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https://github.com/boostorg/python.git
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1 Commits
boost-1.88
...
boost-0.9.
| Author | SHA1 | Date | |
|---|---|---|---|
|
4a8fccf26d |
Binary file not shown.
@@ -1,92 +0,0 @@
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||||
# (C) Copyright David Abrahams 2001. Permission to copy, use, modify, sell and
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||||
# distribute this software is granted provided this copyright notice appears
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||||
# in all copies. This software is provided "as is" without express or implied
|
||||
# warranty, and with no claim as to its suitability for any purpose.
|
||||
#
|
||||
# Boost.Python library Jamfile
|
||||
|
||||
|
||||
# declare the location of this subproject relative to the root
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||||
subproject libs/python/build ;
|
||||
|
||||
# bring in the rules for python
|
||||
import python ;
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||||
|
||||
if [ check-python-config ]
|
||||
{
|
||||
|
||||
local bpl-linkflags ;
|
||||
|
||||
if $(UNIX) && ( $(OS) = AIX )
|
||||
{
|
||||
bpl-linkflags = <linkflags>"-e initlibboost_python" ;
|
||||
}
|
||||
|
||||
# Enabling intrinsics (/0i) or maximize speed (/02) seem to cause
|
||||
# internal compiler errors with this toolset.
|
||||
local msvc-stlport-workarounds
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||||
= <optimization>off "<cxxflags>-Ogty -O1 -Gs" ;
|
||||
|
||||
local sources =
|
||||
numeric.cpp
|
||||
list.cpp
|
||||
long.cpp
|
||||
dict.cpp
|
||||
tuple.cpp
|
||||
str.cpp
|
||||
|
||||
aix_init_module.cpp
|
||||
converter/from_python.cpp
|
||||
converter/registry.cpp
|
||||
converter/type_id.cpp
|
||||
object/enum.cpp
|
||||
object/class.cpp
|
||||
object/function.cpp
|
||||
object/inheritance.cpp
|
||||
object/life_support.cpp
|
||||
object/pickle_support.cpp
|
||||
errors.cpp
|
||||
module.cpp
|
||||
converter/builtin_converters.cpp
|
||||
converter/arg_to_python_base.cpp
|
||||
object/iterator.cpp
|
||||
object_protocol.cpp
|
||||
object_operators.cpp
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||||
;
|
||||
|
||||
dll boost_python
|
||||
: ../src/$(sources)
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||||
: $(BOOST_PYTHON_V2_PROPERTIES)
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||||
<define>BOOST_PYTHON_SOURCE
|
||||
$(bpl-linkflags)
|
||||
<msvc-stlport><release>$(msvc-stlport-workarounds)
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||||
;
|
||||
|
||||
template extension
|
||||
: <dll>boost_python
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||||
: <sysinclude>../../..
|
||||
;
|
||||
|
||||
lib boost_python
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||||
: # sources
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||||
../src/$(sources)
|
||||
|
||||
: # requirements
|
||||
$(BOOST_PYTHON_V2_PROPERTIES)
|
||||
<define>BOOST_PYTHON_SOURCE
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||||
<define>BOOST_STATIC_LIB
|
||||
$(bpl-linkflags)
|
||||
<msvc-stlport><release>$(msvc-stlport-workarounds)
|
||||
;
|
||||
|
||||
stage bin-stage : <dll>boost_python <lib>boost_python
|
||||
: <tag><debug>"_debug"
|
||||
<tag><debug-python>"_pydebug"
|
||||
:
|
||||
debug release
|
||||
;
|
||||
|
||||
install python lib
|
||||
: <dll>boost_python <lib>boost_python
|
||||
;
|
||||
}
|
||||
@@ -1,88 +0,0 @@
|
||||
import os ;
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||||
import modules ;
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||||
|
||||
# Use a very crude way to sense there python is locatted
|
||||
|
||||
|
||||
local PYTHON_PATH = [ modules.peek : PYTHON_PATH ] ;
|
||||
ECHO "XXX" $(PYTHON_PATH) ;
|
||||
|
||||
if [ GLOB /usr/local/include/python2.2 : * ]
|
||||
{
|
||||
PYTHON_PATH = /usr/local ;
|
||||
}
|
||||
else if [ GLOB /usr/include/python2.2 : * ]
|
||||
{
|
||||
PYTHON_PATH = /usr ;
|
||||
}
|
||||
|
||||
if [ os.name ] in CYGWIN NT
|
||||
{
|
||||
lib_condition = <link>shared: ;
|
||||
defines = USE_DL_IMPORT ;
|
||||
|
||||
# Declare a target for the python interpreter library
|
||||
lib python : : <name>python22 <search>$(PYTHON_PATH)/libs ;
|
||||
PYTHON_LIB = python ;
|
||||
}
|
||||
else
|
||||
{
|
||||
lib python : : <name>python2.2 ;
|
||||
PYTHON_LIB = python ;
|
||||
}
|
||||
|
||||
|
||||
|
||||
if $(PYTHON_PATH) {
|
||||
|
||||
|
||||
project boost/python
|
||||
: source-location ../src
|
||||
: requirements <include>$(PYTHON_PATH)/include
|
||||
$(lib_condition)<library-path>$(PYTHON_PATH)/libs
|
||||
<link>shared:<library>$(PYTHON_LIB)
|
||||
<define>$(defines)
|
||||
: usage-requirements # requirement that will be propageted to *users* of this library
|
||||
<include>$(PYTHON_PATH)/include
|
||||
|
||||
# We have a bug which causes us to conclude that conditionalized
|
||||
# properties in this section are not free.
|
||||
# $(lib_condition)<library-path>$(PYTHON_PATH)/lib/python2.2/config
|
||||
# <shared>true:<find-library>$(PYTHON_LIB)
|
||||
|
||||
<library-path>$(PYTHON_PATH)/lib/python2.2/config
|
||||
<library>$(PYTHON_LIB)
|
||||
;
|
||||
|
||||
lib boost_python
|
||||
:
|
||||
numeric.cpp
|
||||
|
||||
list.cpp
|
||||
long.cpp
|
||||
dict.cpp
|
||||
tuple.cpp
|
||||
str.cpp
|
||||
|
||||
aix_init_module.cpp
|
||||
converter/from_python.cpp
|
||||
converter/registry.cpp
|
||||
converter/type_id.cpp
|
||||
object/enum.cpp
|
||||
object/class.cpp
|
||||
object/function.cpp
|
||||
object/inheritance.cpp
|
||||
object/life_support.cpp
|
||||
object/pickle_support.cpp
|
||||
errors.cpp
|
||||
module.cpp
|
||||
converter/builtin_converters.cpp
|
||||
converter/arg_to_python_base.cpp
|
||||
object/iterator.cpp
|
||||
object_protocol.cpp
|
||||
object_operators.cpp
|
||||
: <link>static:<define>BOOST_PYTHON_STATIC_LIB
|
||||
<define>BOOST_PYTHON_SOURCE
|
||||
: <link>shared
|
||||
;
|
||||
}
|
||||
@@ -1,882 +0,0 @@
|
||||
# Microsoft Developer Studio Project File - Name="boost_python" - Package Owner=<4>
|
||||
# Microsoft Developer Studio Generated Build File, Format Version 6.00
|
||||
# ** DO NOT EDIT **
|
||||
|
||||
# TARGTYPE "Win32 (x86) Dynamic-Link Library" 0x0102
|
||||
|
||||
CFG=BOOST_PYTHON - WIN32 RELEASE
|
||||
!MESSAGE This is not a valid makefile. To build this project using NMAKE,
|
||||
!MESSAGE use the Export Makefile command and run
|
||||
!MESSAGE
|
||||
!MESSAGE NMAKE /f "boost_python.mak".
|
||||
!MESSAGE
|
||||
!MESSAGE You can specify a configuration when running NMAKE
|
||||
!MESSAGE by defining the macro CFG on the command line. For example:
|
||||
!MESSAGE
|
||||
!MESSAGE NMAKE /f "boost_python.mak" CFG="BOOST_PYTHON - WIN32 RELEASE"
|
||||
!MESSAGE
|
||||
!MESSAGE Possible choices for configuration are:
|
||||
!MESSAGE
|
||||
!MESSAGE "boost_python - Win32 Release" (based on "Win32 (x86) Dynamic-Link Library")
|
||||
!MESSAGE "boost_python - Win32 Debug" (based on "Win32 (x86) Dynamic-Link Library")
|
||||
!MESSAGE
|
||||
|
||||
# Begin Project
|
||||
# PROP AllowPerConfigDependencies 0
|
||||
# PROP Scc_ProjName ""
|
||||
# PROP Scc_LocalPath ""
|
||||
CPP=cl.exe
|
||||
MTL=midl.exe
|
||||
RSC=rc.exe
|
||||
|
||||
!IF "$(CFG)" == "boost_python - Win32 Release"
|
||||
|
||||
# PROP BASE Use_MFC 0
|
||||
# PROP BASE Use_Debug_Libraries 0
|
||||
# PROP BASE Output_Dir "Release"
|
||||
# PROP BASE Intermediate_Dir "Release"
|
||||
# PROP BASE Target_Dir ""
|
||||
# PROP Use_MFC 0
|
||||
# PROP Use_Debug_Libraries 0
|
||||
# PROP Output_Dir "../bin-stage"
|
||||
# PROP Intermediate_Dir "release-obj"
|
||||
# PROP Ignore_Export_Lib 0
|
||||
# PROP Target_Dir ""
|
||||
F90=df.exe
|
||||
# ADD BASE CPP /nologo /MT /W3 /GX /O2 /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /D "_MBCS" /D "_USRDLL" /D "BPL_EXPORTS" /YX /FD /Zm800 /Zm800 /Zm800 /c
|
||||
# ADD CPP /nologo /MD /W3 /GR /GX /O2 /I "../../../../" /D "NDEBUG" /D "WIN32" /D "_WINDOWS" /D "_MBCS" /D "_USRDLL" /D "BOOST_PYTHON_DYNAMIC_LIB" /D "BOOST_PYTHON_SOURCE" /FD /Zm800 /Zm800 /Zm800 /Zm800 /c
|
||||
# SUBTRACT CPP /YX
|
||||
# ADD BASE MTL /nologo /D "NDEBUG" /mktyplib203 /win32
|
||||
# ADD MTL /nologo /D "NDEBUG" /mktyplib203 /win32
|
||||
# ADD BASE RSC /l 0x1409 /d "NDEBUG"
|
||||
# ADD RSC /l 0x1409 /d "NDEBUG"
|
||||
BSC32=bscmake.exe
|
||||
# ADD BASE BSC32 /nologo
|
||||
# ADD BSC32 /nologo
|
||||
LINK32=link.exe
|
||||
# ADD BASE LINK32 kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib /nologo /dll /machine:I386
|
||||
# ADD LINK32 kernel32.lib user32.lib /nologo /dll /machine:I386
|
||||
|
||||
!ELSEIF "$(CFG)" == "boost_python - Win32 Debug"
|
||||
|
||||
# PROP BASE Use_MFC 0
|
||||
# PROP BASE Use_Debug_Libraries 1
|
||||
# PROP BASE Output_Dir "Debug"
|
||||
# PROP BASE Intermediate_Dir "Debug"
|
||||
# PROP BASE Target_Dir ""
|
||||
# PROP Use_MFC 0
|
||||
# PROP Use_Debug_Libraries 1
|
||||
# PROP Output_Dir "../bin-stage"
|
||||
# PROP Intermediate_Dir "debug-obj"
|
||||
# PROP Ignore_Export_Lib 0
|
||||
# PROP Target_Dir ""
|
||||
F90=df.exe
|
||||
# ADD BASE CPP /nologo /MTd /W3 /Gm /GX /ZI /Od /D "WIN32" /D "_DEBUG" /D "_WINDOWS" /D "_MBCS" /D "_USRDLL" /D "BPL_EXPORTS" /YX /FD /Zm800 /Zm800 /Zm800 /GZ /c
|
||||
# ADD CPP /nologo /MDd /W3 /GR /GX /Zi /Od /I "../../../../" /D "_DEBUG" /D "WIN32" /D "_WINDOWS" /D "_MBCS" /D "_USRDLL" /D "BOOST_PYTHON_DYNAMIC_LIB" /D "BOOST_PYTHON_SOURCE" /FD /Zm800 /Zm800 /Zm800 /Zm800 /Zm800 /GZ /c
|
||||
# ADD BASE MTL /nologo /D "_DEBUG" /mktyplib203 /win32
|
||||
# ADD MTL /nologo /D "_DEBUG" /mktyplib203 /win32
|
||||
# ADD BASE RSC /l 0x1409 /d "_DEBUG"
|
||||
# ADD RSC /l 0x1409 /d "_DEBUG"
|
||||
BSC32=bscmake.exe
|
||||
# ADD BASE BSC32 /nologo
|
||||
# ADD BSC32 /nologo
|
||||
LINK32=link.exe
|
||||
# ADD BASE LINK32 kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib /nologo /dll /debug /machine:I386 /pdbtype:sept
|
||||
# ADD LINK32 kernel32.lib user32.lib /nologo /dll /incremental:no /debug /machine:I386 /out:"../bin-stage/boost_python_debug.dll" /pdbtype:sept
|
||||
|
||||
!ENDIF
|
||||
|
||||
# Begin Target
|
||||
|
||||
# Name "boost_python - Win32 Release"
|
||||
# Name "boost_python - Win32 Debug"
|
||||
# Begin Group "Source Files"
|
||||
|
||||
# PROP Default_Filter "cpp;c;cxx;rc;def;r;odl;idl;hpj;bat"
|
||||
# Begin Source File
|
||||
|
||||
SOURCE=..\..\src\aix_init_module.cpp
|
||||
# End Source File
|
||||
# Begin Source File
|
||||
|
||||
SOURCE=..\..\src\converter\arg_to_python_base.cpp
|
||||
# End Source File
|
||||
# Begin Source File
|
||||
|
||||
SOURCE=..\..\src\converter\builtin_converters.cpp
|
||||
# End Source File
|
||||
# Begin Source File
|
||||
|
||||
SOURCE=..\..\src\object\class.cpp
|
||||
# End Source File
|
||||
# Begin Source File
|
||||
|
||||
SOURCE=..\..\src\dict.cpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\src\object\enum.cpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\src\errors.cpp
|
||||
# End Source File
|
||||
# Begin Source File
|
||||
|
||||
SOURCE=..\..\src\converter\from_python.cpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\src\object\function.cpp
|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\object\iterator.cpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\object\life_support.cpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\list.cpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\long.cpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\module.cpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\numeric.cpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\src\object_operators.cpp
|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\src\tuple.cpp
|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\aix_init_module.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\api_placeholder.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\arg_tuple_size.hpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\borrowed_ptr.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\call_object.hpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\caller.hpp
|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\construct.hpp
|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\force_instantiate.hpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\if_else.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\indirect_traits.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\make_keyword_range_fn.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\make_tuple.hpp
|
||||
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|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\map_entry.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
SOURCE=..\..\..\..\boost\python\detail\member_function_cast.hpp
|
||||
# End Source File
|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
||||
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|
||||
|
||||
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|
||||
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|
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|
||||
|
||||
Package=<4>
|
||||
{{{
|
||||
}}}
|
||||
|
||||
###############################################################################
|
||||
|
||||
Global:
|
||||
|
||||
Package=<5>
|
||||
{{{
|
||||
}}}
|
||||
|
||||
Package=<3>
|
||||
{{{
|
||||
}}}
|
||||
|
||||
###############################################################################
|
||||
|
||||
Binary file not shown.
File diff suppressed because it is too large
Load Diff
Binary file not shown.
@@ -1,947 +0,0 @@
|
||||
+++++++++++++++++++++++++++++++++++++++++++
|
||||
Building Hybrid Systems with Boost.Python
|
||||
+++++++++++++++++++++++++++++++++++++++++++
|
||||
|
||||
:Author: David Abrahams
|
||||
:Contact: dave@boost-consulting.com
|
||||
:organization: `Boost Consulting`_
|
||||
:date: $Date$
|
||||
|
||||
:Author: Ralf W. Grosse-Kunstleve
|
||||
|
||||
:copyright: Copyright David Abrahams and Ralf W. Grosse-Kunstleve 2003. All rights reserved
|
||||
|
||||
.. contents:: Table of Contents
|
||||
|
||||
.. _`Boost Consulting`: http://www.boost-consulting.com
|
||||
|
||||
==========
|
||||
Abstract
|
||||
==========
|
||||
|
||||
Boost.Python is an open source C++ library which provides a concise
|
||||
IDL-like interface for binding C++ classes and functions to
|
||||
Python. Leveraging the full power of C++ compile-time introspection
|
||||
and of recently developed metaprogramming techniques, this is achieved
|
||||
entirely in pure C++, without introducing a new syntax.
|
||||
Boost.Python's rich set of features and high-level interface make it
|
||||
possible to engineer packages from the ground up as hybrid systems,
|
||||
giving programmers easy and coherent access to both the efficient
|
||||
compile-time polymorphism of C++ and the extremely convenient run-time
|
||||
polymorphism of Python.
|
||||
|
||||
==============
|
||||
Introduction
|
||||
==============
|
||||
|
||||
Python and C++ are in many ways as different as two languages could
|
||||
be: while C++ is usually compiled to machine-code, Python is
|
||||
interpreted. Python's dynamic type system is often cited as the
|
||||
foundation of its flexibility, while in C++ static typing is the
|
||||
cornerstone of its efficiency. C++ has an intricate and difficult
|
||||
compile-time meta-language, while in Python, practically everything
|
||||
happens at runtime.
|
||||
|
||||
Yet for many programmers, these very differences mean that Python and
|
||||
C++ complement one another perfectly. Performance bottlenecks in
|
||||
Python programs can be rewritten in C++ for maximal speed, and
|
||||
authors of powerful C++ libraries choose Python as a middleware
|
||||
language for its flexible system integration capabilities.
|
||||
Furthermore, the surface differences mask some strong similarities:
|
||||
|
||||
* 'C'-family control structures (if, while, for...)
|
||||
|
||||
* Support for object-orientation, functional programming, and generic
|
||||
programming (these are both *multi-paradigm* programming languages.)
|
||||
|
||||
* Comprehensive operator overloading facilities, recognizing the
|
||||
importance of syntactic variability for readability and
|
||||
expressivity.
|
||||
|
||||
* High-level concepts such as collections and iterators.
|
||||
|
||||
* High-level encapsulation facilities (C++: namespaces, Python: modules)
|
||||
to support the design of re-usable libraries.
|
||||
|
||||
* Exception-handling for effective management of error conditions.
|
||||
|
||||
* C++ idioms in common use, such as handle/body classes and
|
||||
reference-counted smart pointers mirror Python reference semantics.
|
||||
|
||||
Given Python's rich 'C' interoperability API, it should in principle
|
||||
be possible to expose C++ type and function interfaces to Python with
|
||||
an analogous interface to their C++ counterparts. However, the
|
||||
facilities provided by Python alone for integration with C++ are
|
||||
relatively meager. Compared to C++ and Python, 'C' has only very
|
||||
rudimentary abstraction facilities, and support for exception-handling
|
||||
is completely missing. 'C' extension module writers are required to
|
||||
manually manage Python reference counts, which is both annoyingly
|
||||
tedious and extremely error-prone. Traditional extension modules also
|
||||
tend to contain a great deal of boilerplate code repetition which
|
||||
makes them difficult to maintain, especially when wrapping an evolving
|
||||
API.
|
||||
|
||||
These limitations have lead to the development of a variety of wrapping
|
||||
systems. SWIG_ is probably the most popular package for the
|
||||
integration of C/C++ and Python. A more recent development is SIP_,
|
||||
which was specifically designed for interfacing Python with the Qt_
|
||||
graphical user interface library. Both SWIG and SIP introduce their
|
||||
own specialized languages for customizing inter-language bindings.
|
||||
This has certain advantages, but having to deal with three different
|
||||
languages (Python, C/C++ and the interface language) also introduces
|
||||
practical and mental difficulties. The CXX_ package demonstrates an
|
||||
interesting alternative. It shows that at least some parts of
|
||||
Python's 'C' API can be wrapped and presented through a much more
|
||||
user-friendly C++ interface. However, unlike SWIG and SIP, CXX does
|
||||
not include support for wrapping C++ classes as new Python types.
|
||||
|
||||
The features and goals of Boost.Python_ overlap significantly with
|
||||
many of these other systems. That said, Boost.Python attempts to
|
||||
maximize convenience and flexibility without introducing a separate
|
||||
wrapping language. Instead, it presents the user with a high-level
|
||||
C++ interface for wrapping C++ classes and functions, managing much of
|
||||
the complexity behind-the-scenes with static metaprogramming.
|
||||
Boost.Python also goes beyond the scope of earlier systems by
|
||||
providing:
|
||||
|
||||
* Support for C++ virtual functions that can be overridden in Python.
|
||||
|
||||
* Comprehensive lifetime management facilities for low-level C++
|
||||
pointers and references.
|
||||
|
||||
* Support for organizing extensions as Python packages,
|
||||
with a central registry for inter-language type conversions.
|
||||
|
||||
* A safe and convenient mechanism for tying into Python's powerful
|
||||
serialization engine (pickle).
|
||||
|
||||
* Coherence with the rules for handling C++ lvalues and rvalues that
|
||||
can only come from a deep understanding of both the Python and C++
|
||||
type systems.
|
||||
|
||||
The key insight that sparked the development of Boost.Python is that
|
||||
much of the boilerplate code in traditional extension modules could be
|
||||
eliminated using C++ compile-time introspection. Each argument of a
|
||||
wrapped C++ function must be extracted from a Python object using a
|
||||
procedure that depends on the argument type. Similarly the function's
|
||||
return type determines how the return value will be converted from C++
|
||||
to Python. Of course argument and return types are part of each
|
||||
function's type, and this is exactly the source from which
|
||||
Boost.Python deduces most of the information required.
|
||||
|
||||
This approach leads to *user guided wrapping*: as much information is
|
||||
extracted directly from the source code to be wrapped as is possible
|
||||
within the framework of pure C++, and some additional information is
|
||||
supplied explicitly by the user. Mostly the guidance is mechanical
|
||||
and little real intervention is required. Because the interface
|
||||
specification is written in the same full-featured language as the
|
||||
code being exposed, the user has unprecedented power available when
|
||||
she does need to take control.
|
||||
|
||||
.. _Python: http://www.python.org/
|
||||
.. _SWIG: http://www.swig.org/
|
||||
.. _SIP: http://www.riverbankcomputing.co.uk/sip/index.php
|
||||
.. _Qt: http://www.trolltech.com/
|
||||
.. _CXX: http://cxx.sourceforge.net/
|
||||
.. _Boost.Python: http://www.boost.org/libs/python/doc
|
||||
|
||||
===========================
|
||||
Boost.Python Design Goals
|
||||
===========================
|
||||
|
||||
The primary goal of Boost.Python is to allow users to expose C++
|
||||
classes and functions to Python using nothing more than a C++
|
||||
compiler. In broad strokes, the user experience should be one of
|
||||
directly manipulating C++ objects from Python.
|
||||
|
||||
However, it's also important not to translate all interfaces *too*
|
||||
literally: the idioms of each language must be respected. For
|
||||
example, though C++ and Python both have an iterator concept, they are
|
||||
expressed very differently. Boost.Python has to be able to bridge the
|
||||
interface gap.
|
||||
|
||||
It must be possible to insulate Python users from crashes resulting
|
||||
from trivial misuses of C++ interfaces, such as accessing
|
||||
already-deleted objects. By the same token the library should
|
||||
insulate C++ users from low-level Python 'C' API, replacing
|
||||
error-prone 'C' interfaces like manual reference-count management and
|
||||
raw ``PyObject`` pointers with more-robust alternatives.
|
||||
|
||||
Support for component-based development is crucial, so that C++ types
|
||||
exposed in one extension module can be passed to functions exposed in
|
||||
another without loss of crucial information like C++ inheritance
|
||||
relationships.
|
||||
|
||||
Finally, all wrapping must be *non-intrusive*, without modifying or
|
||||
even seeing the original C++ source code. Existing C++ libraries have
|
||||
to be wrappable by third parties who only have access to header files
|
||||
and binaries.
|
||||
|
||||
==========================
|
||||
Hello Boost.Python World
|
||||
==========================
|
||||
|
||||
And now for a preview of Boost.Python, and how it improves on the raw
|
||||
facilities offered by Python. Here's a function we might want to
|
||||
expose::
|
||||
|
||||
char const* greet(unsigned x)
|
||||
{
|
||||
static char const* const msgs[] = { "hello", "Boost.Python", "world!" };
|
||||
|
||||
if (x > 2)
|
||||
throw std::range_error("greet: index out of range");
|
||||
|
||||
return msgs[x];
|
||||
}
|
||||
|
||||
To wrap this function in standard C++ using the Python 'C' API, we'd
|
||||
need something like this::
|
||||
|
||||
extern "C" // all Python interactions use 'C' linkage and calling convention
|
||||
{
|
||||
// Wrapper to handle argument/result conversion and checking
|
||||
PyObject* greet_wrap(PyObject* args, PyObject * keywords)
|
||||
{
|
||||
int x;
|
||||
if (PyArg_ParseTuple(args, "i", &x)) // extract/check arguments
|
||||
{
|
||||
char const* result = greet(x); // invoke wrapped function
|
||||
return PyString_FromString(result); // convert result to Python
|
||||
}
|
||||
return 0; // error occurred
|
||||
}
|
||||
|
||||
// Table of wrapped functions to be exposed by the module
|
||||
static PyMethodDef methods[] = {
|
||||
{ "greet", greet_wrap, METH_VARARGS, "return one of 3 parts of a greeting" }
|
||||
, { NULL, NULL, 0, NULL } // sentinel
|
||||
};
|
||||
|
||||
// module initialization function
|
||||
DL_EXPORT init_hello()
|
||||
{
|
||||
(void) Py_InitModule("hello", methods); // add the methods to the module
|
||||
}
|
||||
}
|
||||
|
||||
Now here's the wrapping code we'd use to expose it with Boost.Python::
|
||||
|
||||
#include <boost/python.hpp>
|
||||
using namespace boost::python;
|
||||
BOOST_PYTHON_MODULE(hello)
|
||||
{
|
||||
def("greet", greet, "return one of 3 parts of a greeting");
|
||||
}
|
||||
|
||||
and here it is in action::
|
||||
|
||||
>>> import hello
|
||||
>>> for x in range(3):
|
||||
... print hello.greet(x)
|
||||
...
|
||||
hello
|
||||
Boost.Python
|
||||
world!
|
||||
|
||||
Aside from the fact that the 'C' API version is much more verbose,
|
||||
it's worth noting a few things that it doesn't handle correctly:
|
||||
|
||||
* The original function accepts an unsigned integer, and the Python
|
||||
'C' API only gives us a way of extracting signed integers. The
|
||||
Boost.Python version will raise a Python exception if we try to pass
|
||||
a negative number to ``hello.greet``, but the other one will proceed
|
||||
to do whatever the C++ implementation does when converting an
|
||||
negative integer to unsigned (usually wrapping to some very large
|
||||
number), and pass the incorrect translation on to the wrapped
|
||||
function.
|
||||
|
||||
* That brings us to the second problem: if the C++ ``greet()``
|
||||
function is called with a number greater than 2, it will throw an
|
||||
exception. Typically, if a C++ exception propagates across the
|
||||
boundary with code generated by a 'C' compiler, it will cause a
|
||||
crash. As you can see in the first version, there's no C++
|
||||
scaffolding there to prevent this from happening. Functions wrapped
|
||||
by Boost.Python automatically include an exception-handling layer
|
||||
which protects Python users by translating unhandled C++ exceptions
|
||||
into a corresponding Python exception.
|
||||
|
||||
* A slightly more-subtle limitation is that the argument conversion
|
||||
used in the Python 'C' API case can only get that integer ``x`` in
|
||||
*one way*. PyArg_ParseTuple can't convert Python ``long`` objects
|
||||
(arbitrary-precision integers) which happen to fit in an ``unsigned
|
||||
int`` but not in a ``signed long``, nor will it ever handle a
|
||||
wrapped C++ class with a user-defined implicit ``operator unsigned
|
||||
int()`` conversion. Boost.Python's dynamic type conversion
|
||||
registry allows users to add arbitrary conversion methods.
|
||||
|
||||
==================
|
||||
Library Overview
|
||||
==================
|
||||
|
||||
This section outlines some of the library's major features. Except as
|
||||
neccessary to avoid confusion, details of library implementation are
|
||||
omitted.
|
||||
|
||||
------------------
|
||||
Exposing Classes
|
||||
------------------
|
||||
|
||||
C++ classes and structs are exposed with a similarly-terse interface.
|
||||
Given::
|
||||
|
||||
struct World
|
||||
{
|
||||
void set(std::string msg) { this->msg = msg; }
|
||||
std::string greet() { return msg; }
|
||||
std::string msg;
|
||||
};
|
||||
|
||||
The following code will expose it in our extension module::
|
||||
|
||||
#include <boost/python.hpp>
|
||||
BOOST_PYTHON_MODULE(hello)
|
||||
{
|
||||
class_<World>("World")
|
||||
.def("greet", &World::greet)
|
||||
.def("set", &World::set)
|
||||
;
|
||||
}
|
||||
|
||||
Although this code has a certain pythonic familiarity, people
|
||||
sometimes find the syntax bit confusing because it doesn't look like
|
||||
most of the C++ code they're used to. All the same, this is just
|
||||
standard C++. Because of their flexible syntax and operator
|
||||
overloading, C++ and Python are great for defining domain-specific
|
||||
(sub)languages
|
||||
(DSLs), and that's what we've done in Boost.Python. To break it down::
|
||||
|
||||
class_<World>("World")
|
||||
|
||||
constructs an unnamed object of type ``class_<World>`` and passes
|
||||
``"World"`` to its constructor. This creates a new-style Python class
|
||||
called ``World`` in the extension module, and associates it with the
|
||||
C++ type ``World`` in the Boost.Python type conversion registry. We
|
||||
might have also written::
|
||||
|
||||
class_<World> w("World");
|
||||
|
||||
but that would've been more verbose, since we'd have to name ``w``
|
||||
again to invoke its ``def()`` member function::
|
||||
|
||||
w.def("greet", &World::greet)
|
||||
|
||||
There's nothing special about the location of the dot for member
|
||||
access in the original example: C++ allows any amount of whitespace on
|
||||
either side of a token, and placing the dot at the beginning of each
|
||||
line allows us to chain as many successive calls to member functions
|
||||
as we like with a uniform syntax. The other key fact that allows
|
||||
chaining is that ``class_<>`` member functions all return a reference
|
||||
to ``*this``.
|
||||
|
||||
So the example is equivalent to::
|
||||
|
||||
class_<World> w("World");
|
||||
w.def("greet", &World::greet);
|
||||
w.def("set", &World::set);
|
||||
|
||||
It's occasionally useful to be able to break down the components of a
|
||||
Boost.Python class wrapper in this way, but the rest of this article
|
||||
will stick to the terse syntax.
|
||||
|
||||
For completeness, here's the wrapped class in use: ::
|
||||
|
||||
>>> import hello
|
||||
>>> planet = hello.World()
|
||||
>>> planet.set('howdy')
|
||||
>>> planet.greet()
|
||||
'howdy'
|
||||
|
||||
Constructors
|
||||
============
|
||||
|
||||
Since our ``World`` class is just a plain ``struct``, it has an
|
||||
implicit no-argument (nullary) constructor. Boost.Python exposes the
|
||||
nullary constructor by default, which is why we were able to write: ::
|
||||
|
||||
>>> planet = hello.World()
|
||||
|
||||
However, well-designed classes in any language may require constructor
|
||||
arguments in order to establish their invariants. Unlike Python,
|
||||
where ``__init__`` is just a specially-named method, In C++
|
||||
constructors cannot be handled like ordinary member functions. In
|
||||
particular, we can't take their address: ``&World::World`` is an
|
||||
error. The library provides a different interface for specifying
|
||||
constructors. Given::
|
||||
|
||||
struct World
|
||||
{
|
||||
World(std::string msg); // added constructor
|
||||
...
|
||||
|
||||
we can modify our wrapping code as follows::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
...
|
||||
|
||||
of course, a C++ class may have additional constructors, and we can
|
||||
expose those as well by passing more instances of ``init<...>`` to
|
||||
``def()``::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
.def(init<double, double>())
|
||||
...
|
||||
|
||||
Boost.Python allows wrapped functions, member functions, and
|
||||
constructors to be overloaded to mirror C++ overloading.
|
||||
|
||||
Data Members and Properties
|
||||
===========================
|
||||
|
||||
Any publicly-accessible data members in a C++ class can be easily
|
||||
exposed as either ``readonly`` or ``readwrite`` attributes::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
.def_readonly("msg", &World::msg)
|
||||
...
|
||||
|
||||
and can be used directly in Python: ::
|
||||
|
||||
>>> planet = hello.World('howdy')
|
||||
>>> planet.msg
|
||||
'howdy'
|
||||
|
||||
This does *not* result in adding attributes to the ``World`` instance
|
||||
``__dict__``, which can result in substantial memory savings when
|
||||
wrapping large data structures. In fact, no instance ``__dict__``
|
||||
will be created at all unless attributes are explicitly added from
|
||||
Python. Boost.Python owes this capability to the new Python 2.2 type
|
||||
system, in particular the descriptor interface and ``property`` type.
|
||||
|
||||
In C++, publicly-accessible data members are considered a sign of poor
|
||||
design because they break encapsulation, and style guides usually
|
||||
dictate the use of "getter" and "setter" functions instead. In
|
||||
Python, however, ``__getattr__``, ``__setattr__``, and since 2.2,
|
||||
``property`` mean that attribute access is just one more
|
||||
well-encapsulated syntactic tool at the programmer's disposal.
|
||||
Boost.Python bridges this idiomatic gap by making Python ``property``
|
||||
creation directly available to users. If ``msg`` were private, we
|
||||
could still expose it as attribute in Python as follows::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
.add_property("msg", &World::greet, &World::set)
|
||||
...
|
||||
|
||||
The example above mirrors the familiar usage of properties in Python
|
||||
2.2+: ::
|
||||
|
||||
>>> class World(object):
|
||||
... __init__(self, msg):
|
||||
... self.__msg = msg
|
||||
... def greet(self):
|
||||
... return self.__msg
|
||||
... def set(self, msg):
|
||||
... self.__msg = msg
|
||||
... msg = property(greet, set)
|
||||
|
||||
Operator Overloading
|
||||
====================
|
||||
|
||||
The ability to write arithmetic operators for user-defined types has
|
||||
been a major factor in the success of both languages for numerical
|
||||
computation, and the success of packages like NumPy_ attests to the
|
||||
power of exposing operators in extension modules. Boost.Python
|
||||
provides a concise mechanism for wrapping operator overloads. The
|
||||
example below shows a fragment from a wrapper for the Boost rational
|
||||
number library::
|
||||
|
||||
class_<rational<int> >("rational_int")
|
||||
.def(init<int, int>()) // constructor, e.g. rational_int(3,4)
|
||||
.def("numerator", &rational<int>::numerator)
|
||||
.def("denominator", &rational<int>::denominator)
|
||||
.def(-self) // __neg__ (unary minus)
|
||||
.def(self + self) // __add__ (homogeneous)
|
||||
.def(self * self) // __mul__
|
||||
.def(self + int()) // __add__ (heterogenous)
|
||||
.def(int() + self) // __radd__
|
||||
...
|
||||
|
||||
The magic is performed using a simplified application of "expression
|
||||
templates" [VELD1995]_, a technique originally developed for
|
||||
optimization of high-performance matrix algebra expressions. The
|
||||
essence is that instead of performing the computation immediately,
|
||||
operators are overloaded to construct a type *representing* the
|
||||
computation. In matrix algebra, dramatic optimizations are often
|
||||
available when the structure of an entire expression can be taken into
|
||||
account, rather than evaluating each operation "greedily".
|
||||
Boost.Python uses the same technique to build an appropriate Python
|
||||
method object based on expressions involving ``self``.
|
||||
|
||||
.. _NumPy: http://www.pfdubois.com/numpy/
|
||||
|
||||
Inheritance
|
||||
===========
|
||||
|
||||
C++ inheritance relationships can be represented to Boost.Python by adding
|
||||
an optional ``bases<...>`` argument to the ``class_<...>`` template
|
||||
parameter list as follows::
|
||||
|
||||
class_<Derived, bases<Base1,Base2> >("Derived")
|
||||
...
|
||||
|
||||
This has two effects:
|
||||
|
||||
1. When the ``class_<...>`` is created, Python type objects
|
||||
corresponding to ``Base1`` and ``Base2`` are looked up in
|
||||
Boost.Python's registry, and are used as bases for the new Python
|
||||
``Derived`` type object, so methods exposed for the Python ``Base1``
|
||||
and ``Base2`` types are automatically members of the ``Derived``
|
||||
type. Because the registry is global, this works correctly even if
|
||||
``Derived`` is exposed in a different module from either of its
|
||||
bases.
|
||||
|
||||
2. C++ conversions from ``Derived`` to its bases are added to the
|
||||
Boost.Python registry. Thus wrapped C++ methods expecting (a
|
||||
pointer or reference to) an object of either base type can be
|
||||
called with an object wrapping a ``Derived`` instance. Wrapped
|
||||
member functions of class ``T`` are treated as though they have an
|
||||
implicit first argument of ``T&``, so these conversions are
|
||||
neccessary to allow the base class methods to be called for derived
|
||||
objects.
|
||||
|
||||
Of course it's possible to derive new Python classes from wrapped C++
|
||||
class instances. Because Boost.Python uses the new-style class
|
||||
system, that works very much as for the Python built-in types. There
|
||||
is one significant detail in which it differs: the built-in types
|
||||
generally establish their invariants in their ``__new__`` function, so
|
||||
that derived classes do not need to call ``__init__`` on the base
|
||||
class before invoking its methods : ::
|
||||
|
||||
>>> class L(list):
|
||||
... def __init__(self):
|
||||
... pass
|
||||
...
|
||||
>>> L().reverse()
|
||||
>>>
|
||||
|
||||
Because C++ object construction is a one-step operation, C++ instance
|
||||
data cannot be constructed until the arguments are available, in the
|
||||
``__init__`` function: ::
|
||||
|
||||
>>> class D(SomeBoostPythonClass):
|
||||
... def __init__(self):
|
||||
... pass
|
||||
...
|
||||
>>> D().some_boost_python_method()
|
||||
Traceback (most recent call last):
|
||||
File "<stdin>", line 1, in ?
|
||||
TypeError: bad argument type for built-in operation
|
||||
|
||||
This happened because Boost.Python couldn't find instance data of type
|
||||
``SomeBoostPythonClass`` within the ``D`` instance; ``D``'s ``__init__``
|
||||
function masked construction of the base class. It could be corrected
|
||||
by either removing ``D``'s ``__init__`` function or having it call
|
||||
``SomeBoostPythonClass.__init__(...)`` explicitly.
|
||||
|
||||
Virtual Functions
|
||||
=================
|
||||
|
||||
Deriving new types in Python from extension classes is not very
|
||||
interesting unless they can be used polymorphically from C++. In
|
||||
other words, Python method implementations should appear to override
|
||||
the implementation of C++ virtual functions when called *through base
|
||||
class pointers/references from C++*. Since the only way to alter the
|
||||
behavior of a virtual function is to override it in a derived class,
|
||||
the user must build a special derived class to dispatch a polymorphic
|
||||
class' virtual functions::
|
||||
|
||||
//
|
||||
// interface to wrap:
|
||||
//
|
||||
class Base
|
||||
{
|
||||
public:
|
||||
virtual int f(std::string x) { return 42; }
|
||||
virtual ~Base();
|
||||
};
|
||||
|
||||
int calls_f(Base const& b, std::string x) { return b.f(x); }
|
||||
|
||||
//
|
||||
// Wrapping Code
|
||||
//
|
||||
|
||||
// Dispatcher class
|
||||
struct BaseWrap : Base
|
||||
{
|
||||
// Store a pointer to the Python object
|
||||
BaseWrap(PyObject* self_) : self(self_) {}
|
||||
PyObject* self;
|
||||
|
||||
// Default implementation, for when f is not overridden
|
||||
int f_default(std::string x) { return this->Base::f(x); }
|
||||
// Dispatch implementation
|
||||
int f(std::string x) { return call_method<int>(self, "f", x); }
|
||||
};
|
||||
|
||||
...
|
||||
def("calls_f", calls_f);
|
||||
class_<Base, BaseWrap>("Base")
|
||||
.def("f", &Base::f, &BaseWrap::f_default)
|
||||
;
|
||||
|
||||
Now here's some Python code which demonstrates: ::
|
||||
|
||||
>>> class Derived(Base):
|
||||
... def f(self, s):
|
||||
... return len(s)
|
||||
...
|
||||
>>> calls_f(Base(), 'foo')
|
||||
42
|
||||
>>> calls_f(Derived(), 'forty-two')
|
||||
9
|
||||
|
||||
Things to notice about the dispatcher class:
|
||||
|
||||
* The key element which allows overriding in Python is the
|
||||
``call_method`` invocation, which uses the same global type
|
||||
conversion registry as the C++ function wrapping does to convert its
|
||||
arguments from C++ to Python and its return type from Python to C++.
|
||||
|
||||
* Any constructor signatures you wish to wrap must be replicated with
|
||||
an initial ``PyObject*`` argument
|
||||
|
||||
* The dispatcher must store this argument so that it can be used to
|
||||
invoke ``call_method``
|
||||
|
||||
* The ``f_default`` member function is needed when the function being
|
||||
exposed is not pure virtual; there's no other way ``Base::f`` can be
|
||||
called on an object of type ``BaseWrap``, since it overrides ``f``.
|
||||
|
||||
Deeper Reflection on the Horizon?
|
||||
=================================
|
||||
|
||||
Admittedly, this formula is tedious to repeat, especially on a project
|
||||
with many polymorphic classes. That it is neccessary reflects some
|
||||
limitations in C++'s compile-time introspection capabilities: there's
|
||||
no way to enumerate the members of a class and find out which are
|
||||
virtual functions. At least one very promising project has been
|
||||
started to write a front-end which can generate these dispatchers (and
|
||||
other wrapping code) automatically from C++ headers.
|
||||
|
||||
Pyste_ is being developed by Bruno da Silva de Oliveira. It builds on
|
||||
GCC_XML_, which generates an XML version of GCC's internal program
|
||||
representation. Since GCC is a highly-conformant C++ compiler, this
|
||||
ensures correct handling of the most-sophisticated template code and
|
||||
full access to the underlying type system. In keeping with the
|
||||
Boost.Python philosophy, a Pyste interface description is neither
|
||||
intrusive on the code being wrapped, nor expressed in some unfamiliar
|
||||
language: instead it is a 100% pure Python script. If Pyste is
|
||||
successful it will mark a move away from wrapping everything directly
|
||||
in C++ for many of our users. It will also allow us the choice to
|
||||
shift some of the metaprogram code from C++ to Python. We expect that
|
||||
soon, not only our users but the Boost.Python developers themselves
|
||||
will be "thinking hybrid" about their own code.
|
||||
|
||||
.. _`GCC_XML`: http://www.gccxml.org/HTML/Index.html
|
||||
.. _`Pyste`: http://www.boost.org/libs/python/pyste
|
||||
|
||||
---------------
|
||||
Serialization
|
||||
---------------
|
||||
|
||||
*Serialization* is the process of converting objects in memory to a
|
||||
form that can be stored on disk or sent over a network connection. The
|
||||
serialized object (most often a plain string) can be retrieved and
|
||||
converted back to the original object. A good serialization system will
|
||||
automatically convert entire object hierarchies. Python's standard
|
||||
``pickle`` module is just such a system. It leverages the language's strong
|
||||
runtime introspection facilities for serializing practically arbitrary
|
||||
user-defined objects. With a few simple and unintrusive provisions this
|
||||
powerful machinery can be extended to also work for wrapped C++ objects.
|
||||
Here is an example::
|
||||
|
||||
#include <string>
|
||||
|
||||
struct World
|
||||
{
|
||||
World(std::string a_msg) : msg(a_msg) {}
|
||||
std::string greet() const { return msg; }
|
||||
std::string msg;
|
||||
};
|
||||
|
||||
#include <boost/python.hpp>
|
||||
using namespace boost::python;
|
||||
|
||||
struct World_picklers : pickle_suite
|
||||
{
|
||||
static tuple
|
||||
getinitargs(World const& w) { return make_tuple(w.greet()); }
|
||||
};
|
||||
|
||||
BOOST_PYTHON_MODULE(hello)
|
||||
{
|
||||
class_<World>("World", init<std::string>())
|
||||
.def("greet", &World::greet)
|
||||
.def_pickle(World_picklers())
|
||||
;
|
||||
}
|
||||
|
||||
Now let's create a ``World`` object and put it to rest on disk::
|
||||
|
||||
>>> import hello
|
||||
>>> import pickle
|
||||
>>> a_world = hello.World("howdy")
|
||||
>>> pickle.dump(a_world, open("my_world", "w"))
|
||||
|
||||
In a potentially *different script* on a potentially *different
|
||||
computer* with a potentially *different operating system*::
|
||||
|
||||
>>> import pickle
|
||||
>>> resurrected_world = pickle.load(open("my_world", "r"))
|
||||
>>> resurrected_world.greet()
|
||||
'howdy'
|
||||
|
||||
Of course the ``cPickle`` module can also be used for faster
|
||||
processing.
|
||||
|
||||
Boost.Python's ``pickle_suite`` fully supports the ``pickle`` protocol
|
||||
defined in the standard Python documentation. Like a __getinitargs__
|
||||
function in Python, the pickle_suite's getinitargs() is responsible for
|
||||
creating the argument tuple that will be use to reconstruct the pickled
|
||||
object. The other elements of the Python pickling protocol,
|
||||
__getstate__ and __setstate__ can be optionally provided via C++
|
||||
getstate and setstate functions. C++'s static type system allows the
|
||||
library to ensure at compile-time that nonsensical combinations of
|
||||
functions (e.g. getstate without setstate) are not used.
|
||||
|
||||
Enabling serialization of more complex C++ objects requires a little
|
||||
more work than is shown in the example above. Fortunately the
|
||||
``object`` interface (see next section) greatly helps in keeping the
|
||||
code manageable.
|
||||
|
||||
------------------
|
||||
Object interface
|
||||
------------------
|
||||
|
||||
Experienced 'C' language extension module authors will be familiar
|
||||
with the ubiquitous ``PyObject*``, manual reference-counting, and the
|
||||
need to remember which API calls return "new" (owned) references or
|
||||
"borrowed" (raw) references. These constraints are not just
|
||||
cumbersome but also a major source of errors, especially in the
|
||||
presence of exceptions.
|
||||
|
||||
Boost.Python provides a class ``object`` which automates reference
|
||||
counting and provides conversion to Python from C++ objects of
|
||||
arbitrary type. This significantly reduces the learning effort for
|
||||
prospective extension module writers.
|
||||
|
||||
Creating an ``object`` from any other type is extremely simple::
|
||||
|
||||
object s("hello, world"); // s manages a Python string
|
||||
|
||||
``object`` has templated interactions with all other types, with
|
||||
automatic to-python conversions. It happens so naturally that it's
|
||||
easily overlooked::
|
||||
|
||||
object ten_Os = 10 * s[4]; // -> "oooooooooo"
|
||||
|
||||
In the example above, ``4`` and ``10`` are converted to Python objects
|
||||
before the indexing and multiplication operations are invoked.
|
||||
|
||||
The ``extract<T>`` class template can be used to convert Python objects
|
||||
to C++ types::
|
||||
|
||||
double x = extract<double>(o);
|
||||
|
||||
If a conversion in either direction cannot be performed, an
|
||||
appropriate exception is thrown at runtime.
|
||||
|
||||
The ``object`` type is accompanied by a set of derived types
|
||||
that mirror the Python built-in types such as ``list``, ``dict``,
|
||||
``tuple``, etc. as much as possible. This enables convenient
|
||||
manipulation of these high-level types from C++::
|
||||
|
||||
dict d;
|
||||
d["some"] = "thing";
|
||||
d["lucky_number"] = 13;
|
||||
list l = d.keys();
|
||||
|
||||
This almost looks and works like regular Python code, but it is pure
|
||||
C++. Of course we can wrap C++ functions which accept or return
|
||||
``object`` instances.
|
||||
|
||||
=================
|
||||
Thinking hybrid
|
||||
=================
|
||||
|
||||
Because of the practical and mental difficulties of combining
|
||||
programming languages, it is common to settle a single language at the
|
||||
outset of any development effort. For many applications, performance
|
||||
considerations dictate the use of a compiled language for the core
|
||||
algorithms. Unfortunately, due to the complexity of the static type
|
||||
system, the price we pay for runtime performance is often a
|
||||
significant increase in development time. Experience shows that
|
||||
writing maintainable C++ code usually takes longer and requires *far*
|
||||
more hard-earned working experience than developing comparable Python
|
||||
code. Even when developers are comfortable working exclusively in
|
||||
compiled languages, they often augment their systems by some type of
|
||||
ad hoc scripting layer for the benefit of their users without ever
|
||||
availing themselves of the same advantages.
|
||||
|
||||
Boost.Python enables us to *think hybrid*. Python can be used for
|
||||
rapidly prototyping a new application; its ease of use and the large
|
||||
pool of standard libraries give us a head start on the way to a
|
||||
working system. If necessary, the working code can be used to
|
||||
discover rate-limiting hotspots. To maximize performance these can
|
||||
be reimplemented in C++, together with the Boost.Python bindings
|
||||
needed to tie them back into the existing higher-level procedure.
|
||||
|
||||
Of course, this *top-down* approach is less attractive if it is clear
|
||||
from the start that many algorithms will eventually have to be
|
||||
implemented in C++. Fortunately Boost.Python also enables us to
|
||||
pursue a *bottom-up* approach. We have used this approach very
|
||||
successfully in the development of a toolbox for scientific
|
||||
applications. The toolbox started out mainly as a library of C++
|
||||
classes with Boost.Python bindings, and for a while the growth was
|
||||
mainly concentrated on the C++ parts. However, as the toolbox is
|
||||
becoming more complete, more and more newly added functionality can be
|
||||
implemented in Python.
|
||||
|
||||
.. image:: python_cpp_mix.jpg
|
||||
|
||||
This figure shows the estimated ratio of newly added C++ and Python
|
||||
code over time as new algorithms are implemented. We expect this
|
||||
ratio to level out near 70% Python. Being able to solve new problems
|
||||
mostly in Python rather than a more difficult statically typed
|
||||
language is the return on our investment in Boost.Python. The ability
|
||||
to access all of our code from Python allows a broader group of
|
||||
developers to use it in the rapid development of new applications.
|
||||
|
||||
=====================
|
||||
Development history
|
||||
=====================
|
||||
|
||||
The first version of Boost.Python was developed in 2000 by Dave
|
||||
Abrahams at Dragon Systems, where he was privileged to have Tim Peters
|
||||
as a guide to "The Zen of Python". One of Dave's jobs was to develop
|
||||
a Python-based natural language processing system. Since it was
|
||||
eventually going to be targeting embedded hardware, it was always
|
||||
assumed that the compute-intensive core would be rewritten in C++ to
|
||||
optimize speed and memory footprint [#proto]_. The project also wanted to
|
||||
test all of its C++ code using Python test scripts [#test]_. The only
|
||||
tool we knew of for binding C++ and Python was SWIG_, and at the time
|
||||
its handling of C++ was weak. It would be false to claim any deep
|
||||
insight into the possible advantages of Boost.Python's approach at
|
||||
this point. Dave's interest and expertise in fancy C++ template
|
||||
tricks had just reached the point where he could do some real damage,
|
||||
and Boost.Python emerged as it did because it filled a need and
|
||||
because it seemed like a cool thing to try.
|
||||
|
||||
This early version was aimed at many of the same basic goals we've
|
||||
described in this paper, differing most-noticeably by having a
|
||||
slightly more cumbersome syntax and by lack of special support for
|
||||
operator overloading, pickling, and component-based development.
|
||||
These last three features were quickly added by Ullrich Koethe and
|
||||
Ralf Grosse-Kunstleve [#feature]_, and other enthusiastic contributors arrived
|
||||
on the scene to contribute enhancements like support for nested
|
||||
modules and static member functions.
|
||||
|
||||
By early 2001 development had stabilized and few new features were
|
||||
being added, however a disturbing new fact came to light: Ralf had
|
||||
begun testing Boost.Python on pre-release versions of a compiler using
|
||||
the EDG_ front-end, and the mechanism at the core of Boost.Python
|
||||
responsible for handling conversions between Python and C++ types was
|
||||
failing to compile. As it turned out, we had been exploiting a very
|
||||
common bug in the implementation of all the C++ compilers we had
|
||||
tested. We knew that as C++ compilers rapidly became more
|
||||
standards-compliant, the library would begin failing on more
|
||||
platforms. Unfortunately, because the mechanism was so central to the
|
||||
functioning of the library, fixing the problem looked very difficult.
|
||||
|
||||
Fortunately, later that year Lawrence Berkeley and later Lawrence
|
||||
Livermore National labs contracted with `Boost Consulting`_ for support
|
||||
and development of Boost.Python, and there was a new opportunity to
|
||||
address fundamental issues and ensure a future for the library. A
|
||||
redesign effort began with the low level type conversion architecture,
|
||||
building in standards-compliance and support for component-based
|
||||
development (in contrast to version 1 where conversions had to be
|
||||
explicitly imported and exported across module boundaries). A new
|
||||
analysis of the relationship between the Python and C++ objects was
|
||||
done, resulting in more intuitive handling for C++ lvalues and
|
||||
rvalues.
|
||||
|
||||
The emergence of a powerful new type system in Python 2.2 made the
|
||||
choice of whether to maintain compatibility with Python 1.5.2 easy:
|
||||
the opportunity to throw away a great deal of elaborate code for
|
||||
emulating classic Python classes alone was too good to pass up. In
|
||||
addition, Python iterators and descriptors provided crucial and
|
||||
elegant tools for representing similar C++ constructs. The
|
||||
development of the generalized ``object`` interface allowed us to
|
||||
further shield C++ programmers from the dangers and syntactic burdens
|
||||
of the Python 'C' API. A great number of other features including C++
|
||||
exception translation, improved support for overloaded functions, and
|
||||
most significantly, CallPolicies for handling pointers and
|
||||
references, were added during this period.
|
||||
|
||||
In October 2002, version 2 of Boost.Python was released. Development
|
||||
since then has concentrated on improved support for C++ runtime
|
||||
polymorphism and smart pointers. Peter Dimov's ingenious
|
||||
``boost::shared_ptr`` design in particular has allowed us to give the
|
||||
hybrid developer a consistent interface for moving objects back and
|
||||
forth across the language barrier without loss of information. At
|
||||
first, we were concerned that the sophistication and complexity of the
|
||||
Boost.Python v2 implementation might discourage contributors, but the
|
||||
emergence of Pyste_ and several other significant feature
|
||||
contributions have laid those fears to rest. Daily questions on the
|
||||
Python C++-sig and a backlog of desired improvements show that the
|
||||
library is getting used. To us, the future looks bright.
|
||||
|
||||
.. _`EDG`: http://www.edg.com
|
||||
|
||||
=============
|
||||
Conclusions
|
||||
=============
|
||||
|
||||
Boost.Python achieves seamless interoperability between two rich and
|
||||
complimentary language environments. Because it leverages template
|
||||
metaprogramming to introspect about types and functions, the user
|
||||
never has to learn a third syntax: the interface definitions are
|
||||
written in concise and maintainable C++. Also, the wrapping system
|
||||
doesn't have to parse C++ headers or represent the type system: the
|
||||
compiler does that work for us.
|
||||
|
||||
Computationally intensive tasks play to the strengths of C++ and are
|
||||
often impossible to implement efficiently in pure Python, while jobs
|
||||
like serialization that are trivial in Python can be very difficult in
|
||||
pure C++. Given the luxury of building a hybrid software system from
|
||||
the ground up, we can approach design with new confidence and power.
|
||||
|
||||
===========
|
||||
Citations
|
||||
===========
|
||||
|
||||
.. [VELD1995] T. Veldhuizen, "Expression Templates," C++ Report,
|
||||
Vol. 7 No. 5 June 1995, pp. 26-31.
|
||||
http://osl.iu.edu/~tveldhui/papers/Expression-Templates/exprtmpl.html
|
||||
|
||||
===========
|
||||
Footnotes
|
||||
===========
|
||||
|
||||
.. [#proto] In retrospect, it seems that "thinking hybrid" from the
|
||||
ground up might have been better for the NLP system: the
|
||||
natural component boundaries defined by the pure python
|
||||
prototype turned out to be inappropriate for getting the
|
||||
desired performance and memory footprint out of the C++ core,
|
||||
which eventually caused some redesign overhead on the Python
|
||||
side when the core was moved to C++.
|
||||
|
||||
.. [#test] We also have some reservations about driving all C++
|
||||
testing through a Python interface, unless that's the only way
|
||||
it will be ultimately used. Any transition across language
|
||||
boundaries with such different object models can inevitably
|
||||
mask bugs.
|
||||
|
||||
.. [#feature] These features were expressed very differently in v1 of
|
||||
Boost.Python
|
||||
@@ -1,908 +0,0 @@
|
||||
.. This is a comment. Note how any initial comments are moved by
|
||||
transforms to after the document title, subtitle, and docinfo.
|
||||
|
||||
.. Need intro and conclusion
|
||||
.. Exposing classes
|
||||
.. Constructors
|
||||
.. Overloading
|
||||
.. Properties and data members
|
||||
.. Inheritance
|
||||
.. Operators and Special Functions
|
||||
.. Virtual Functions
|
||||
.. Call Policies
|
||||
|
||||
++++++++++++++++++++++++++++++++++++++++++++++
|
||||
Introducing Boost.Python (Extended Abstract)
|
||||
++++++++++++++++++++++++++++++++++++++++++++++
|
||||
|
||||
|
||||
.. bibliographic fields (which also require a transform):
|
||||
|
||||
:Author: David Abrahams
|
||||
:Address: 45 Walnut Street
|
||||
Somerville, MA 02143
|
||||
:Contact: dave@boost-consulting.com
|
||||
:organization: `Boost Consulting`_
|
||||
:date: $Date$
|
||||
:status: This is a "work in progress"
|
||||
:version: 1
|
||||
:copyright: Copyright David Abrahams 2002. All rights reserved
|
||||
|
||||
:Dedication:
|
||||
|
||||
For my girlfriend, wife, and partner Luann
|
||||
|
||||
:abstract:
|
||||
|
||||
This paper describes the Boost.Python library, a system for
|
||||
C++/Python interoperability.
|
||||
|
||||
.. meta::
|
||||
:keywords: Boost,python,Boost.Python,C++
|
||||
:description lang=en: C++/Python interoperability with Boost.Python
|
||||
|
||||
.. contents:: Table of Contents
|
||||
.. section-numbering::
|
||||
|
||||
|
||||
.. _`Boost Consulting`: http://www.boost-consulting.com
|
||||
|
||||
==============
|
||||
Introduction
|
||||
==============
|
||||
|
||||
Python and C++ are in many ways as different as two languages could
|
||||
be: while C++ is usually compiled to machine-code, Python is
|
||||
interpreted. Python's dynamic type system is often cited as the
|
||||
foundation of its flexibility, while in C++ static typing is the
|
||||
cornerstone of its efficiency. C++ has an intricate and difficult
|
||||
meta-language to support compile-time polymorphism, while Python is
|
||||
a uniform language with convenient runtime polymorphism.
|
||||
|
||||
Yet for many programmers, these very differences mean that Python and
|
||||
C++ complement one another perfectly. Performance bottlenecks in
|
||||
Python programs can be rewritten in C++ for maximal speed, and
|
||||
authors of powerful C++ libraries choose Python as a middleware
|
||||
language for its flexible system integration capabilities.
|
||||
Furthermore, the surface differences mask some strong similarities:
|
||||
|
||||
* 'C'-family control structures (if, while, for...)
|
||||
|
||||
* Support for object-orientation, functional programming, and generic
|
||||
programming (these are both *multi-paradigm* programming languages.)
|
||||
|
||||
* Comprehensive operator overloading facilities, recognizing the
|
||||
importance of syntactic variability for readability and
|
||||
expressivity.
|
||||
|
||||
* High-level concepts such as collections and iterators.
|
||||
|
||||
* High-level encapsulation facilities (C++: namespaces, Python: modules)
|
||||
to support the design of re-usable libraries.
|
||||
|
||||
* Exception-handling for effective management of error conditions.
|
||||
|
||||
* C++ idioms in common use, such as handle/body classes and
|
||||
reference-counted smart pointers mirror Python reference semantics.
|
||||
|
||||
Python provides a rich 'C' API for writers of 'C' extension modules.
|
||||
Unfortunately, using this API directly for exposing C++ type and
|
||||
function interfaces to Python is much more tedious than it should be.
|
||||
This is mainly due to the limitations of the 'C' language. Compared to
|
||||
C++ and Python, 'C' has only very rudimentary abstraction facilities.
|
||||
Support for exception-handling is completely missing. One important
|
||||
undesirable consequence is that 'C' extension module writers are
|
||||
required to manually manage Python reference counts. Another unpleasant
|
||||
consequence is a very high degree of repetition of similar code in 'C'
|
||||
extension modules. Of course highly redundant code does not only cause
|
||||
frustration for the module writer, but is also very difficult to
|
||||
maintain.
|
||||
|
||||
The limitations of the 'C' API have lead to the development of a
|
||||
variety of wrapping systems. SWIG_ is probably the most popular package
|
||||
for the integration of C/C++ and Python. A more recent development is
|
||||
the SIP_ package, which is specifically designed for interfacing Python
|
||||
with the Qt_ graphical user interface library. Both SWIG and SIP
|
||||
introduce a new specialized language for defining the inter-language
|
||||
bindings. Of course being able to use a specialized language has
|
||||
advantages, but having to deal with three different languages (Python,
|
||||
C/C++ and the interface language) also introduces practical and mental
|
||||
difficulties. The CXX_ package demonstrates an interesting alternative.
|
||||
It shows that at least some parts of Python's 'C' API can be wrapped
|
||||
and presented through a much more user-friendly C++ interface. However,
|
||||
unlike SWIG and SIP, CXX does not include support for wrapping C++
|
||||
classes as new Python types. CXX is also no longer actively developed.
|
||||
|
||||
In some respects Boost.Python combines ideas from SWIG and SIP with
|
||||
ideas from CXX. Like SWIG and SIP, Boost.Python is a system for
|
||||
wrapping C++ classes as new Python "built-in" types, and C/C++
|
||||
functions as Python functions. Like CXX, Boost.Python presents Python's
|
||||
'C' API through a C++ interface. Boost.Python goes beyond the scope of
|
||||
other systems with the unique support for C++ virtual functions that
|
||||
are overrideable in Python, support for organizing extensions as Python
|
||||
packages with a central registry for inter-language type conversions,
|
||||
and a convenient mechanism for tying into Python's serialization engine
|
||||
(pickle). Importantly, all this is achieved without introducing a new
|
||||
syntax. Boost.Python leverages the power of C++ meta-programming
|
||||
techniques to introspect about the C++ type system, and presents a
|
||||
simple, IDL-like C++ interface for exposing C/C++ code in extension
|
||||
modules. Boost.Python is a pure C++ library, the inter-language
|
||||
bindings are defined in pure C++, and other than a C++ compiler only
|
||||
Python itself is required to get started with Boost.Python. Last but
|
||||
not least, Boost.Python is an unrestricted open source library. There
|
||||
are no strings attached even for commercial applications.
|
||||
|
||||
.. _SWIG: http://www.swig.org/
|
||||
.. _SIP: http://www.riverbankcomputing.co.uk/sip/index.php
|
||||
.. _Qt: http://www.trolltech.com/
|
||||
.. _CXX: http://cxx.sourceforge.net/
|
||||
|
||||
===========================
|
||||
Boost.Python Design Goals
|
||||
===========================
|
||||
|
||||
The primary goal of Boost.Python is to allow users to expose C++
|
||||
classes and functions to Python using nothing more than a C++
|
||||
compiler. In broad strokes, the user experience should be one of
|
||||
directly manipulating C++ objects from Python.
|
||||
|
||||
However, it's also important not to translate all interfaces *too*
|
||||
literally: the idioms of each language must be respected. For
|
||||
example, though C++ and Python both have an iterator concept, they are
|
||||
expressed very differently. Boost.Python has to be able to bridge the
|
||||
interface gap.
|
||||
|
||||
It must be possible to insulate Python users from crashes resulting
|
||||
from trivial misuses of C++ interfaces, such as accessing
|
||||
already-deleted objects. By the same token the library should
|
||||
insulate C++ users from low-level Python 'C' API, replacing
|
||||
error-prone 'C' interfaces like manual reference-count management and
|
||||
raw ``PyObject`` pointers with more-robust alternatives.
|
||||
|
||||
Support for component-based development is crucial, so that C++ types
|
||||
exposed in one extension module can be passed to functions exposed in
|
||||
another without loss of crucial information like C++ inheritance
|
||||
relationships.
|
||||
|
||||
Finally, all wrapping must be *non-intrusive*, without modifying or
|
||||
even seeing the original C++ source code. Existing C++ libraries have
|
||||
to be wrappable by third parties who only have access to header files
|
||||
and binaries.
|
||||
|
||||
==========================
|
||||
Hello Boost.Python World
|
||||
==========================
|
||||
|
||||
And now for a preview of Boost.Python, and how it improves on the raw
|
||||
facilities offered by Python. Here's a function we might want to
|
||||
expose::
|
||||
|
||||
char const* greet(unsigned x)
|
||||
{
|
||||
static char const* const msgs[] = { "hello", "Boost.Python", "world!" };
|
||||
|
||||
if (x > 2)
|
||||
throw std::range_error("greet: index out of range");
|
||||
|
||||
return msgs[x];
|
||||
}
|
||||
|
||||
To wrap this function in standard C++ using the Python 'C' API, we'd
|
||||
need something like this::
|
||||
|
||||
extern "C" // all Python interactions use 'C' linkage and calling convention
|
||||
{
|
||||
// Wrapper to handle argument/result conversion and checking
|
||||
PyObject* greet_wrap(PyObject* args, PyObject * keywords)
|
||||
{
|
||||
int x;
|
||||
if (PyArg_ParseTuple(args, "i", &x)) // extract/check arguments
|
||||
{
|
||||
char const* result = greet(x); // invoke wrapped function
|
||||
return PyString_FromString(result); // convert result to Python
|
||||
}
|
||||
return 0; // error occurred
|
||||
}
|
||||
|
||||
// Table of wrapped functions to be exposed by the module
|
||||
static PyMethodDef methods[] = {
|
||||
{ "greet", greet_wrap, METH_VARARGS, "return one of 3 parts of a greeting" }
|
||||
, { NULL, NULL, 0, NULL } // sentinel
|
||||
};
|
||||
|
||||
// module initialization function
|
||||
DL_EXPORT init_hello()
|
||||
{
|
||||
(void) Py_InitModule("hello", methods); // add the methods to the module
|
||||
}
|
||||
}
|
||||
|
||||
Now here's the wrapping code we'd use to expose it with Boost.Python::
|
||||
|
||||
#include <boost/python.hpp>
|
||||
using namespace boost::python;
|
||||
BOOST_PYTHON_MODULE(hello)
|
||||
{
|
||||
def("greet", greet, "return one of 3 parts of a greeting");
|
||||
}
|
||||
|
||||
and here it is in action::
|
||||
|
||||
>>> import hello
|
||||
>>> for x in range(3):
|
||||
... print hello.greet(x)
|
||||
...
|
||||
hello
|
||||
Boost.Python
|
||||
world!
|
||||
|
||||
Aside from the fact that the 'C' API version is much more verbose than
|
||||
the BPL one, it's worth noting that it doesn't handle a few things
|
||||
correctly:
|
||||
|
||||
* The original function accepts an unsigned integer, and the Python
|
||||
'C' API only gives us a way of extracting signed integers. The
|
||||
Boost.Python version will raise a Python exception if we try to pass
|
||||
a negative number to ``hello.greet``, but the other one will proceed
|
||||
to do whatever the C++ implementation does when converting an
|
||||
negative integer to unsigned (usually wrapping to some very large
|
||||
number), and pass the incorrect translation on to the wrapped
|
||||
function.
|
||||
|
||||
* That brings us to the second problem: if the C++ ``greet()``
|
||||
function is called with a number greater than 2, it will throw an
|
||||
exception. Typically, if a C++ exception propagates across the
|
||||
boundary with code generated by a 'C' compiler, it will cause a
|
||||
crash. As you can see in the first version, there's no C++
|
||||
scaffolding there to prevent this from happening. Functions wrapped
|
||||
by Boost.Python automatically include an exception-handling layer
|
||||
which protects Python users by translating unhandled C++ exceptions
|
||||
into a corresponding Python exception.
|
||||
|
||||
* A slightly more-subtle limitation is that the argument conversion
|
||||
used in the Python 'C' API case can only get that integer ``x`` in
|
||||
*one way*. PyArg_ParseTuple can't convert Python ``long`` objects
|
||||
(arbitrary-precision integers) which happen to fit in an ``unsigned
|
||||
int`` but not in a ``signed long``, nor will it ever handle a
|
||||
wrapped C++ class with a user-defined implicit ``operator unsigned
|
||||
int()`` conversion. The BPL's dynamic type conversion registry
|
||||
allows users to add arbitrary conversion methods.
|
||||
|
||||
==================
|
||||
Library Overview
|
||||
==================
|
||||
|
||||
This section outlines some of the library's major features. Except as
|
||||
neccessary to avoid confusion, details of library implementation are
|
||||
omitted.
|
||||
|
||||
-------------------------------------------
|
||||
The fundamental type-conversion mechanism
|
||||
-------------------------------------------
|
||||
|
||||
XXX This needs to be rewritten.
|
||||
|
||||
Every argument of every wrapped function requires some kind of
|
||||
extraction code to convert it from Python to C++. Likewise, the
|
||||
function return value has to be converted from C++ to Python.
|
||||
Appropriate Python exceptions must be raised if the conversion fails.
|
||||
Argument and return types are part of the function's type, and much of
|
||||
this tedium can be relieved if the wrapping system can extract that
|
||||
information through introspection.
|
||||
|
||||
Passing a wrapped C++ derived class instance to a C++ function
|
||||
accepting a pointer or reference to a base class requires knowledge of
|
||||
the inheritance relationship and how to translate the address of a base
|
||||
class into that of a derived class.
|
||||
|
||||
------------------
|
||||
Exposing Classes
|
||||
------------------
|
||||
|
||||
C++ classes and structs are exposed with a similarly-terse interface.
|
||||
Given::
|
||||
|
||||
struct World
|
||||
{
|
||||
void set(std::string msg) { this->msg = msg; }
|
||||
std::string greet() { return msg; }
|
||||
std::string msg;
|
||||
};
|
||||
|
||||
The following code will expose it in our extension module::
|
||||
|
||||
#include <boost/python.hpp>
|
||||
BOOST_PYTHON_MODULE(hello)
|
||||
{
|
||||
class_<World>("World")
|
||||
.def("greet", &World::greet)
|
||||
.def("set", &World::set)
|
||||
;
|
||||
}
|
||||
|
||||
Although this code has a certain pythonic familiarity, people
|
||||
sometimes find the syntax bit confusing because it doesn't look like
|
||||
most of the C++ code they're used to. All the same, this is just
|
||||
standard C++. Because of their flexible syntax and operator
|
||||
overloading, C++ and Python are great for defining domain-specific
|
||||
(sub)languages
|
||||
(DSLs), and that's what we've done in BPL. To break it down::
|
||||
|
||||
class_<World>("World")
|
||||
|
||||
constructs an unnamed object of type ``class_<World>`` and passes
|
||||
``"World"`` to its constructor. This creates a new-style Python class
|
||||
called ``World`` in the extension module, and associates it with the
|
||||
C++ type ``World`` in the BPL type conversion registry. We might have
|
||||
also written::
|
||||
|
||||
class_<World> w("World");
|
||||
|
||||
but that would've been more verbose, since we'd have to name ``w``
|
||||
again to invoke its ``def()`` member function::
|
||||
|
||||
w.def("greet", &World::greet)
|
||||
|
||||
There's nothing special about the location of the dot for member
|
||||
access in the original example: C++ allows any amount of whitespace on
|
||||
either side of a token, and placing the dot at the beginning of each
|
||||
line allows us to chain as many successive calls to member functions
|
||||
as we like with a uniform syntax. The other key fact that allows
|
||||
chaining is that ``class_<>`` member functions all return a reference
|
||||
to ``*this``.
|
||||
|
||||
So the example is equivalent to::
|
||||
|
||||
class_<World> w("World");
|
||||
w.def("greet", &World::greet);
|
||||
w.def("set", &World::set);
|
||||
|
||||
It's occasionally useful to be able to break down the components of a
|
||||
Boost.Python class wrapper in this way, but the rest of this paper
|
||||
will tend to stick to the terse syntax.
|
||||
|
||||
For completeness, here's the wrapped class in use:
|
||||
|
||||
>>> import hello
|
||||
>>> planet = hello.World()
|
||||
>>> planet.set('howdy')
|
||||
>>> planet.greet()
|
||||
'howdy'
|
||||
|
||||
Constructors
|
||||
============
|
||||
|
||||
Since our ``World`` class is just a plain ``struct``, it has an
|
||||
implicit no-argument (nullary) constructor. Boost.Python exposes the
|
||||
nullary constructor by default, which is why we were able to write:
|
||||
|
||||
>>> planet = hello.World()
|
||||
|
||||
However, well-designed classes in any language may require constructor
|
||||
arguments in order to establish their invariants. Unlike Python,
|
||||
where ``__init__`` is just a specially-named method, In C++
|
||||
constructors cannot be handled like ordinary member functions. In
|
||||
particular, we can't take their address: ``&World::World`` is an
|
||||
error. The library provides a different interface for specifying
|
||||
constructors. Given::
|
||||
|
||||
struct World
|
||||
{
|
||||
World(std::string msg); // added constructor
|
||||
...
|
||||
|
||||
we can modify our wrapping code as follows::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
...
|
||||
|
||||
of course, a C++ class may have additional constructors, and we can
|
||||
expose those as well by passing more instances of ``init<...>`` to
|
||||
``def()``::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
.def(init<double, double>())
|
||||
...
|
||||
|
||||
Boost.Python allows wrapped functions, member functions, and
|
||||
constructors to be overloaded to mirror C++ overloading.
|
||||
|
||||
Data Members and Properties
|
||||
===========================
|
||||
|
||||
Any publicly-accessible data members in a C++ class can be easily
|
||||
exposed as either ``readonly`` or ``readwrite`` attributes::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
.def_readonly("msg", &World::msg)
|
||||
...
|
||||
|
||||
and can be used directly in Python:
|
||||
|
||||
>>> planet = hello.World('howdy')
|
||||
>>> planet.msg
|
||||
'howdy'
|
||||
|
||||
This does *not* result in adding attributes to the ``World`` instance
|
||||
``__dict__``, which can result in substantial memory savings when
|
||||
wrapping large data structures. In fact, no instance ``__dict__``
|
||||
will be created at all unless attributes are explicitly added from
|
||||
Python. BPL owes this capability to the new Python 2.2 type system,
|
||||
in particular the descriptor interface and ``property`` type.
|
||||
|
||||
In C++, publicly-accessible data members are considered a sign of poor
|
||||
design because they break encapsulation, and style guides usually
|
||||
dictate the use of "getter" and "setter" functions instead. In
|
||||
Python, however, ``__getattr__``, ``__setattr__``, and since 2.2,
|
||||
``property`` mean that attribute access is just one more
|
||||
well-encapsulated syntactic tool at the programmer's disposal. BPL
|
||||
bridges this idiomatic gap by making Python ``property`` creation
|
||||
directly available to users. So if ``msg`` were private, we could
|
||||
still expose it as attribute in Python as follows::
|
||||
|
||||
class_<World>("World", init<std::string>())
|
||||
.add_property("msg", &World::greet, &World::set)
|
||||
...
|
||||
|
||||
The example above mirrors the familiar usage of properties in Python
|
||||
2.2+:
|
||||
|
||||
>>> class World(object):
|
||||
... __init__(self, msg):
|
||||
... self.__msg = msg
|
||||
... def greet(self):
|
||||
... return self.__msg
|
||||
... def set(self, msg):
|
||||
... self.__msg = msg
|
||||
... msg = property(greet, set)
|
||||
|
||||
Operators and Special Functions
|
||||
===============================
|
||||
|
||||
The ability to write arithmetic operators for user-defined types that
|
||||
C++ and Python both allow the definition of has been a major factor in
|
||||
the popularity of both languages for scientific computing. The
|
||||
success of packages like NumPy attests to the power of exposing
|
||||
operators in extension modules. In this example we'll wrap a class
|
||||
representing a position in a large file::
|
||||
|
||||
class FilePos { /*...*/ };
|
||||
|
||||
// Linear offset
|
||||
FilePos operator+(FilePos, int);
|
||||
FilePos operator+(int, FilePos);
|
||||
FilePos operator-(FilePos, int);
|
||||
|
||||
// Distance between two FilePos objects
|
||||
int operator-(FilePos, FilePos);
|
||||
|
||||
// Offset with assignment
|
||||
FilePos& operator+=(FilePos&, int);
|
||||
FilePos& operator-=(FilePos&, int);
|
||||
|
||||
// Comparison
|
||||
bool operator<(FilePos, FilePos);
|
||||
|
||||
The wrapping code looks like this::
|
||||
|
||||
class_<FilePos>("FilePos")
|
||||
.def(self + int()) // __add__
|
||||
.def(int() + self) // __radd__
|
||||
.def(self - int()) // __sub__
|
||||
|
||||
.def(self - self) // __sub__
|
||||
|
||||
.def(self += int()) // __iadd__
|
||||
.def(self -= int()) // __isub__
|
||||
|
||||
.def(self < self); // __lt__
|
||||
;
|
||||
|
||||
The magic is performed using a simplified application of "expression
|
||||
templates" [VELD1995]_, a technique originally developed by for
|
||||
optimization of high-performance matrix algebra expressions. The
|
||||
essence is that instead of performing the computation immediately,
|
||||
operators are overloaded to construct a type *representing* the
|
||||
computation. In matrix algebra, dramatic optimizations are often
|
||||
available when the structure of an entire expression can be taken into
|
||||
account, rather than processing each operation "greedily".
|
||||
Boost.Python uses the same technique to build an appropriate Python
|
||||
callable object based on an expression involving ``self``, which is
|
||||
then added to the class.
|
||||
|
||||
Inheritance
|
||||
===========
|
||||
|
||||
C++ inheritance relationships can be represented to Boost.Python by adding
|
||||
an optional ``bases<...>`` argument to the ``class_<...>`` template
|
||||
parameter list as follows::
|
||||
|
||||
class_<Derived, bases<Base1,Base2> >("Derived")
|
||||
...
|
||||
|
||||
This has two effects:
|
||||
|
||||
1. When the ``class_<...>`` is created, Python type objects
|
||||
corresponding to ``Base1`` and ``Base2`` are looked up in the BPL
|
||||
registry, and are used as bases for the new Python ``Derived`` type
|
||||
object [#mi]_, so methods exposed for the Python ``Base1`` and
|
||||
``Base2`` types are automatically members of the ``Derived`` type.
|
||||
Because the registry is global, this works correctly even if
|
||||
``Derived`` is exposed in a different module from either of its
|
||||
bases.
|
||||
|
||||
2. C++ conversions from ``Derived`` to its bases are added to the
|
||||
Boost.Python registry. Thus wrapped C++ methods expecting (a
|
||||
pointer or reference to) an object of either base type can be
|
||||
called with an object wrapping a ``Derived`` instance. Wrapped
|
||||
member functions of class ``T`` are treated as though they have an
|
||||
implicit first argument of ``T&``, so these conversions are
|
||||
neccessary to allow the base class methods to be called for derived
|
||||
objects.
|
||||
|
||||
Of course it's possible to derive new Python classes from wrapped C++
|
||||
class instances. Because Boost.Python uses the new-style class
|
||||
system, that works very much as for the Python built-in types. There
|
||||
is one significant detail in which it differs: the built-in types
|
||||
generally establish their invariants in their ``__new__`` function, so
|
||||
that derived classes do not need to call ``__init__`` on the base
|
||||
class before invoking its methods :
|
||||
|
||||
>>> class L(list):
|
||||
... def __init__(self):
|
||||
... pass
|
||||
...
|
||||
>>> L().reverse()
|
||||
>>>
|
||||
|
||||
Because C++ object construction is a one-step operation, C++ instance
|
||||
data cannot be constructed until the arguments are available, in the
|
||||
``__init__`` function:
|
||||
|
||||
>>> class D(SomeBPLClass):
|
||||
... def __init__(self):
|
||||
... pass
|
||||
...
|
||||
>>> D().some_bpl_method()
|
||||
Traceback (most recent call last):
|
||||
File "<stdin>", line 1, in ?
|
||||
TypeError: bad argument type for built-in operation
|
||||
|
||||
This happened because Boost.Python couldn't find instance data of type
|
||||
``SomeBPLClass`` within the ``D`` instance; ``D``'s ``__init__``
|
||||
function masked construction of the base class. It could be corrected
|
||||
by either removing ``D``'s ``__init__`` function or having it call
|
||||
``SomeBPLClass.__init__(...)`` explicitly.
|
||||
|
||||
Virtual Functions
|
||||
=================
|
||||
|
||||
Deriving new types in Python from extension classes is not very
|
||||
interesting unless they can be used polymorphically from C++. In
|
||||
other words, Python method implementations should appear to override
|
||||
the implementation of C++ virtual functions when called *through base
|
||||
class pointers/references from C++*. Since the only way to alter the
|
||||
behavior of a virtual function is to override it in a derived class,
|
||||
the user must build a special derived class to dispatch a polymorphic
|
||||
class' virtual functions::
|
||||
|
||||
//
|
||||
// interface to wrap:
|
||||
//
|
||||
class Base
|
||||
{
|
||||
public:
|
||||
virtual int f(std::string x) { return 42; }
|
||||
virtual ~Base();
|
||||
};
|
||||
|
||||
int calls_f(Base const& b, std::string x) { return b.f(x); }
|
||||
|
||||
//
|
||||
// Wrapping Code
|
||||
//
|
||||
|
||||
// Dispatcher class
|
||||
struct BaseWrap : Base
|
||||
{
|
||||
// Store a pointer to the Python object
|
||||
BaseWrap(PyObject* self_) : self(self_) {}
|
||||
PyObject* self;
|
||||
|
||||
// Default implementation, for when f is not overridden
|
||||
int f_default(std::string x) { return this->Base::f(x); }
|
||||
// Dispatch implementation
|
||||
int f(std::string x) { return call_method<int>(self, "f", x); }
|
||||
};
|
||||
|
||||
...
|
||||
def("calls_f", calls_f);
|
||||
class_<Base, BaseWrap>("Base")
|
||||
.def("f", &Base::f, &BaseWrap::f_default)
|
||||
;
|
||||
|
||||
Now here's some Python code which demonstrates:
|
||||
|
||||
>>> class Derived(Base):
|
||||
... def f(self, s):
|
||||
... return len(s)
|
||||
...
|
||||
>>> calls_f(Base(), 'foo')
|
||||
42
|
||||
>>> calls_f(Derived(), 'forty-two')
|
||||
9
|
||||
|
||||
Things to notice about the dispatcher class:
|
||||
|
||||
* The key element which allows overriding in Python is the
|
||||
``call_method`` invocation, which uses the same global type
|
||||
conversion registry as the C++ function wrapping does to convert its
|
||||
arguments from C++ to Python and its return type from Python to C++.
|
||||
|
||||
* Any constructor signatures you wish to wrap must be replicated with
|
||||
an initial ``PyObject*`` argument
|
||||
|
||||
* The dispatcher must store this argument so that it can be used to
|
||||
invoke ``call_method``
|
||||
|
||||
* The ``f_default`` member function is needed when the function being
|
||||
exposed is not pure virtual; there's no other way ``Base::f`` can be
|
||||
called on an object of type ``BaseWrap``, since it overrides ``f``.
|
||||
|
||||
Admittedly, this formula is tedious to repeat, especially on a project
|
||||
with many polymorphic classes; that it is neccessary reflects
|
||||
limitations in C++'s compile-time reflection capabilities. Several
|
||||
efforts are underway to write front-ends for Boost.Python which can
|
||||
generate these dispatchers (and other wrapping code) automatically.
|
||||
If these are successful it will mark a move away from wrapping
|
||||
everything directly in pure C++ for many of our users.
|
||||
|
||||
---------------
|
||||
Serialization
|
||||
---------------
|
||||
|
||||
*Serialization* is the process of converting objects in memory to a
|
||||
form that can be stored on disk or sent over a network connection. The
|
||||
serialized object (most often a plain string) can be retrieved and
|
||||
converted back to the original object. A good serialization system will
|
||||
automatically convert entire object hierarchies. Python's standard
|
||||
``pickle`` module is such a system. It leverages the language's strong
|
||||
runtime introspection facilities for serializing practically arbitrary
|
||||
user-defined objects. With a few simple and unintrusive provisions this
|
||||
powerful machinery can be extended to also work for wrapped C++ objects.
|
||||
Here is an example::
|
||||
|
||||
#include <string>
|
||||
|
||||
struct World
|
||||
{
|
||||
World(std::string a_msg) : msg(a_msg) {}
|
||||
std::string greet() const { return msg; }
|
||||
std::string msg;
|
||||
};
|
||||
|
||||
#include <boost/python.hpp>
|
||||
using namespace boost::python;
|
||||
|
||||
struct World_picklers : pickle_suite
|
||||
{
|
||||
static tuple
|
||||
getinitargs(World const& w) { return make_tuple(w.greet()); }
|
||||
};
|
||||
|
||||
BOOST_PYTHON_MODULE(hello)
|
||||
{
|
||||
class_<World>("World", init<std::string>())
|
||||
.def("greet", &World::greet)
|
||||
.def_pickle(World_picklers())
|
||||
;
|
||||
}
|
||||
|
||||
Now let's create a ``World`` object and put it to rest on disk::
|
||||
|
||||
>>> import hello
|
||||
>>> import pickle
|
||||
>>> a_world = hello.World("howdy")
|
||||
>>> pickle.dump(a_world, open("my_world", "w"))
|
||||
|
||||
In a potentially *different script* on a potentially *different
|
||||
computer* with a potentially *different operating system*::
|
||||
|
||||
>>> import pickle
|
||||
>>> resurrected_world = pickle.load(open("my_world", "r"))
|
||||
>>> resurrected_world.greet()
|
||||
'howdy'
|
||||
|
||||
Of course the ``cPickle`` module can also be used for faster
|
||||
processing.
|
||||
|
||||
Boost.Python's ``pickle_suite`` fully supports the ``pickle`` protocol
|
||||
defined in the standard Python documentation. There is a one-to-one
|
||||
correspondence between the standard pickling methods (``__getinitargs__``,
|
||||
``__getstate__``, ``__setstate__``) and the functions defined by the
|
||||
user in the class derived from ``pickle_suite`` (``getinitargs``,
|
||||
``getstate``, ``setstate``). The ``class_::def_pickle()`` member function
|
||||
is used to establish the Python bindings for all user-defined functions
|
||||
simultaneously. Correct signatures for these functions are enforced at
|
||||
compile time. Non-sensical combinations of the three pickle functions
|
||||
are also rejected at compile time. These measures are designed to
|
||||
help the user in avoiding obvious errors.
|
||||
|
||||
Enabling serialization of more complex C++ objects requires a little
|
||||
more work than is shown in the example above. Fortunately the
|
||||
``object`` interface (see next section) greatly helps in keeping the
|
||||
code manageable.
|
||||
|
||||
------------------
|
||||
Object interface
|
||||
------------------
|
||||
|
||||
Experienced extension module authors will be familiar with the 'C' view
|
||||
of Python objects, the ubiquitous ``PyObject*``. Most if not all Python
|
||||
'C' API functions involve ``PyObject*`` as arguments or return type. A
|
||||
major complication is the raw reference counting interface presented to
|
||||
the 'C' programmer. E.g. some API functions return *new references* and
|
||||
others return *borrowed references*. It is up to the extension module
|
||||
writer to properly increment and decrement reference counts. This
|
||||
quickly becomes cumbersome and error prone, especially if there are
|
||||
multiple execution paths.
|
||||
|
||||
Boost.Python provides a type ``object`` which is essentially a high
|
||||
level wrapper around ``PyObject*``. ``object`` automates reference
|
||||
counting as much as possible. It also provides the facilities for
|
||||
converting arbitrary C++ types to Python objects and vice versa.
|
||||
This significantly reduces the learning effort for prospective
|
||||
extension module writers.
|
||||
|
||||
Creating an ``object`` from any other type is extremely simple::
|
||||
|
||||
object o(3);
|
||||
|
||||
``object`` has templated interactions with all other types, with
|
||||
automatic to-python conversions. It happens so naturally that it's
|
||||
easily overlooked.
|
||||
|
||||
The ``extract<T>`` class template can be used to convert Python objects
|
||||
to C++ types::
|
||||
|
||||
double x = extract<double>(o);
|
||||
|
||||
All registered user-defined conversions are automatically accessible
|
||||
through the ``object`` interface. With reference to the ``World`` class
|
||||
defined in previous examples::
|
||||
|
||||
object as_python_object(World("howdy"));
|
||||
World back_as_c_plus_plus_object = extract<World>(as_python_object);
|
||||
|
||||
If a C++ type cannot be converted to a Python object an appropriate
|
||||
exception is thrown at runtime. Similarly, an appropriate exception is
|
||||
thrown if a C++ type cannot be extracted from a Python object.
|
||||
``extract<T>`` provides facilities for avoiding exceptions if this is
|
||||
desired.
|
||||
|
||||
The ``object::attr()`` member function is available for accessing
|
||||
and manipulating attributes of Python objects. For example::
|
||||
|
||||
object planet(World());
|
||||
planet.attr("set")("howdy");
|
||||
|
||||
``planet.attr("set")`` returns a callable ``object``. ``"howdy"`` is
|
||||
converted to a Python string object which is then passed as an argument
|
||||
to the ``set`` method.
|
||||
|
||||
The ``object`` type is accompanied by a set of derived types
|
||||
that mirror the Python built-in types such as ``list``, ``dict``,
|
||||
``tuple``, etc. as much as possible. This enables convenient
|
||||
manipulation of these high-level types from C++::
|
||||
|
||||
dict d;
|
||||
d["some"] = "thing";
|
||||
d["lucky_number"] = 13;
|
||||
list l = d.keys();
|
||||
|
||||
This almost looks and works like regular Python code, but it is pure C++.
|
||||
|
||||
=================
|
||||
Thinking hybrid
|
||||
=================
|
||||
|
||||
For many applications runtime performance considerations are very
|
||||
important. This is particularly true for most scientific applications.
|
||||
Often the performance considerations dictate the use of a compiled
|
||||
language for the core algorithms. Traditionally the decision to use a
|
||||
particular programming language is an exclusive one. Because of the
|
||||
practical and mental difficulties of combining different languages many
|
||||
systems are written in just one language. This is quite unfortunate
|
||||
because the price payed for runtime performance is typically a
|
||||
significant overhead due to static typing. For example, our experience
|
||||
shows that developing maintainable C++ code is typically much more
|
||||
time-consuming and requires much more hard-earned working experience
|
||||
than developing useful Python code. A related observation is that many
|
||||
compiled packages are augmented by some type of rudimentary scripting
|
||||
layer. These ad hoc solutions clearly show that many times a compiled
|
||||
language alone does not get the job done. On the other hand it is also
|
||||
clear that a pure Python implementation is too slow for numerically
|
||||
intensive production code.
|
||||
|
||||
Boost.Python enables us to *think hybrid* when developing new
|
||||
applications. Python can be used for rapidly prototyping a
|
||||
new application. Python's ease of use and the large pool of standard
|
||||
libraries give us a head start on the way to a first working system. If
|
||||
necessary, the working procedure can be used to discover the
|
||||
rate-limiting algorithms. To maximize performance these can be
|
||||
reimplemented in C++, together with the Boost.Python bindings needed to
|
||||
tie them back into the existing higher-level procedure.
|
||||
|
||||
Of course, this *top-down* approach is less attractive if it is clear
|
||||
from the start that many algorithms will eventually have to be
|
||||
implemented in a compiled language. Fortunately Boost.Python also
|
||||
enables us to pursue a *bottom-up* approach. We have used this approach
|
||||
very successfully in the development of a toolbox for scientific
|
||||
applications (scitbx) that we will describe elsewhere. The toolbox
|
||||
started out mainly as a library of C++ classes with Boost.Python
|
||||
bindings, and for a while the growth was mainly concentrated on the C++
|
||||
parts. However, as the toolbox is becoming more complete, more and more
|
||||
newly added functionality can be implemented in Python. We expect this
|
||||
trend to continue, as illustrated qualitatively in this figure:
|
||||
|
||||
.. image:: python_cpp_mix.png
|
||||
|
||||
This figure shows the ratio of newly added C++ and Python code over
|
||||
time as new algorithms are implemented. We expect this ratio to level
|
||||
out near 70% Python. The increasing ability to solve new problems
|
||||
mostly with the easy-to-use Python language rather than a necessarily
|
||||
more arcane statically typed language is the return on the investment
|
||||
of learning how to use Boost.Python. The ability to solve some problems
|
||||
entirely using only Python will enable a larger group of people to
|
||||
participate in the rapid development of new applications.
|
||||
|
||||
=============
|
||||
Conclusions
|
||||
=============
|
||||
|
||||
The examples in this paper illustrate that Boost.Python enables
|
||||
seamless interoperability between C++ and Python. Importantly, this is
|
||||
achieved without introducing a third syntax: the Python/C++ interface
|
||||
definitions are written in pure C++. This avoids any problems with
|
||||
parsing the C++ code to be interfaced to Python, yet the interface
|
||||
definitions are concise and maintainable. Freed from most of the
|
||||
development-time penalties of crossing a language boundary, software
|
||||
designers can take full advantage of two rich and complimentary
|
||||
language environments. In practice it turns out that some things are
|
||||
very difficult to do with pure Python/C (e.g. an efficient array
|
||||
library with an intuitive interface in the compiled language) and
|
||||
others are very difficult to do with pure C++ (e.g. serialization).
|
||||
If one has the luxury of being able to design a software system as a
|
||||
hybrid system from the ground up there are many new ways of avoiding
|
||||
road blocks in one language or the other.
|
||||
|
||||
.. I'm not ready to give up on all of this quite yet
|
||||
|
||||
.. Perhaps one day we'll have a language with the simplicity and
|
||||
expressive power of Python and the compile-time muscle of C++. Being
|
||||
able to take advantage of all of these facilities without paying the
|
||||
mental and development-time penalties of crossing a language barrier
|
||||
would bring enormous benefits. Until then, interoperability tools
|
||||
like Boost.Python can help lower the barrier and make the benefits of
|
||||
both languages more accessible to both communities.
|
||||
|
||||
===========
|
||||
Footnotes
|
||||
===========
|
||||
|
||||
.. [#mi] For hard-core new-style class/extension module writers it is
|
||||
worth noting that the normal requirement that all extension classes
|
||||
with data form a layout-compatible single-inheritance chain is
|
||||
lifted for Boost.Python extension classes. Clearly, either
|
||||
``Base1`` or ``Base2`` has to occupy a different offset in the
|
||||
``Derived`` class instance. This is possible because the wrapped
|
||||
part of BPL extension class instances is never assumed to have a
|
||||
fixed offset within the wrapper.
|
||||
|
||||
===========
|
||||
Citations
|
||||
===========
|
||||
|
||||
.. [VELD1995] T. Veldhuizen, "Expression Templates," C++ Report,
|
||||
Vol. 7 No. 5 June 1995, pp. 26-31.
|
||||
http://osl.iu.edu/~tveldhui/papers/Expression-Templates/exprtmpl.html
|
||||
@@ -1,188 +0,0 @@
|
||||
/*
|
||||
:Author: David Goodger
|
||||
:Contact: goodger@users.sourceforge.net
|
||||
:date: $Date$
|
||||
:version: $Revision$
|
||||
:copyright: This stylesheet has been placed in the public domain.
|
||||
|
||||
Default cascading style sheet for the HTML output of Docutils.
|
||||
*/
|
||||
|
||||
.first {
|
||||
margin-top: 0 }
|
||||
|
||||
.last {
|
||||
margin-bottom: 0 }
|
||||
|
||||
a.toc-backref {
|
||||
text-decoration: none ;
|
||||
color: black }
|
||||
|
||||
dd {
|
||||
margin-bottom: 0.5em }
|
||||
|
||||
div.abstract {
|
||||
margin: 2em 5em }
|
||||
|
||||
div.abstract p.topic-title {
|
||||
font-weight: bold ;
|
||||
text-align: center }
|
||||
|
||||
div.attention, div.caution, div.danger, div.error, div.hint,
|
||||
div.important, div.note, div.tip, div.warning {
|
||||
margin: 2em ;
|
||||
border: medium outset ;
|
||||
padding: 1em }
|
||||
|
||||
div.attention p.admonition-title, div.caution p.admonition-title,
|
||||
div.danger p.admonition-title, div.error p.admonition-title,
|
||||
div.warning p.admonition-title {
|
||||
color: red ;
|
||||
font-weight: bold ;
|
||||
font-family: sans-serif }
|
||||
|
||||
div.hint p.admonition-title, div.important p.admonition-title,
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="boost.css">
|
||||
|
||||
<title>Boost.Python - Building and Testing</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Building and Testing</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="Reference">
|
||||
<dt><a href="#requirements">Requirements</a></dt>
|
||||
|
||||
<dt><a href="#building">Building Boost.Python</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="index">
|
||||
<dt><a href="#configuration">Configuration</a></dt>
|
||||
|
||||
<dt><a href="#cygwin_configuration">Configuration for Cygwin GCC
|
||||
from a Windows prompt</a></dt>
|
||||
|
||||
<dt><a href="#results">Results</a></dt>
|
||||
|
||||
<dt><a href="#cygwin">Notes for Cygwin GCC Users</a></dt>
|
||||
|
||||
<dt><a href="#mingw">Notes for MinGW (and Cygwin with -mno-cygwin)
|
||||
GCC Users</a></dt>
|
||||
|
||||
<dt><a href="#testing">Testing</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#building_ext">Building your Extension Module</a></dt>
|
||||
|
||||
<dt><a href="#variants">Build Variants</a></dt>
|
||||
|
||||
<dt><a href="#VisualStudio">Building Using the Microsoft Visual Studio
|
||||
IDE</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="requirements">Requirements</a></h2>
|
||||
<b>Boost.Python</b> version 2 requires <a href=
|
||||
"http://www.python.org/2.2">Python 2.2</a> <i>or <a href=
|
||||
"http://www.python.org">newer</a></i>. An unsupported archive of
|
||||
Boost.Python version 1, which works with versions of Python since 1.5.2,
|
||||
is available <a href="../build/python_v1.zip">here</a>.
|
||||
|
||||
<h2><a name="building">Building Boost.Python</a></h2>
|
||||
|
||||
<p>Normally, Boost.Python extension modules must be linked with the
|
||||
<code>boost_python</code> shared library. In special circumstances you
|
||||
may want to link to a static version of the <code>boost_python</code>
|
||||
library, but if multiple Boost.Python extension modules are used
|
||||
together, it will prevent sharing of types across extension modules, and
|
||||
consume extra code space. To build <code>boost_python</code>, use <a
|
||||
href="../../../tools/build/index.html">Boost.Build</a> in the usual way
|
||||
from the <code>libs/python/build</code> subdirectory of your boost
|
||||
installation (if you have already built boost from the top level this may
|
||||
have no effect, since the work is already done).</p>
|
||||
|
||||
<h3><a name="configuration">Basic Configuration</a></h3>
|
||||
You may need to configure the following variables to point Boost.Build at
|
||||
your Python installation:
|
||||
|
||||
<table border="1" summary="build configuration variables">
|
||||
<tr>
|
||||
<th>Variable Name</th>
|
||||
|
||||
<th>Semantics</th>
|
||||
|
||||
<th>Default</th>
|
||||
|
||||
<th>Notes</th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>PYTHON_ROOT</code></td>
|
||||
|
||||
<td>The root directory of your Python installation</td>
|
||||
|
||||
<td>Windows: <code>c:/tools/python</code>
|
||||
Unix: <code>/usr/local</code></td>
|
||||
|
||||
<td>On Unix, this is the <code>--with-prefix=</code> directory used
|
||||
to configure Python</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>PYTHON_VERSION</code></td>
|
||||
|
||||
<td>The The 2-part python Major.Minor version number</td>
|
||||
|
||||
<td><code>2.2</code></td>
|
||||
|
||||
<td>Be sure not to include a third number, e.g. <b>not</b>
|
||||
"<code>2.2.1</code>", even if that's the version you have.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>PYTHON_INCLUDES</code></td>
|
||||
|
||||
<td>path to Python <code>#include</code> directories</td>
|
||||
|
||||
<td>Autoconfigured from <code>PYTHON_ROOT</code>. Try the default
|
||||
before attempting to set it yourself.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>PYTHON_LIB_PATH</code></td>
|
||||
|
||||
<td>path to Python library object.</td>
|
||||
|
||||
<td>Autoconfigured from <code>PYTHON_ROOT</code>. Try the default
|
||||
before attempting to set it yourself.</td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h3><a name="cygwin_configuration">Configuration for Cygwin GCC from a
|
||||
Windows prompt</a></h3>
|
||||
The following settings may be useful when building with <a href=
|
||||
"http://www.cygwin.com">Cygwin</a> GCC (not MinGW) from a Windows command
|
||||
shell using a Windows build of <code>bjam</code>. <b>If
|
||||
"<code>bjam -v</code>" does not report "<code>OS=NT</code>", these
|
||||
settings do not apply to you</b>; you should use the <a href=
|
||||
"#configuration">normal configuration</a> variables instead. They are
|
||||
only useful when building and testing with multiple toolsets on Windows
|
||||
using a single build command, since Cygwin GCC requires a different build
|
||||
of Python.
|
||||
|
||||
<table border="1" summary=
|
||||
"Cygwin GCC under NT build configuration variables">
|
||||
<tr>
|
||||
<th>Variable Name</th>
|
||||
|
||||
<th>Semantics</th>
|
||||
|
||||
<th>Default</th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>CYGWIN_PYTHON_[DEBUG_]VERSION</code></td>
|
||||
|
||||
<td>The version of python being used under Cygwin.</td>
|
||||
|
||||
<td>$(PYTHON_VERSION)</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>CYGWIN_PYTHON_[DEBUG_]ROOT</code></td>
|
||||
|
||||
<td>unix-style path containing the <code>include/</code> directory
|
||||
containing
|
||||
<code>python$(CYGWIN_PYTHON_[DEBUG_]VERSION)/python.h</code>.</td>
|
||||
|
||||
<td>$(PYTHON_ROOT)</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>CYGWIN_PYTHON_[DEBUG_]LIB_PATH</code></td>
|
||||
|
||||
<td>path containing the user's Cygwin Python import lib
|
||||
<code>libpython$(CYGWIN_PYTHON_[DEBUG_]VERSION).dll.a</code></td>
|
||||
|
||||
<td>Autoconfigured from <code>CYGWIN_PYTHON_ROOT</code></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>CYGWIN_PYTHON_[DEBUG_]DLL_PATH</code></td>
|
||||
|
||||
<td>path containing the user's Cygwin Python dll
|
||||
(<code>libpython$(CYGWIN_PYTHON_[DEBUG_]VERSION).dll</code>)</td>
|
||||
|
||||
<td><code>/bin</code></td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h3><a name="cygwin">Notes for Cygwin GCC Users</a></h3>
|
||||
|
||||
<p>If you are using Cygwin GCC to build extension modules, you must use a
|
||||
Cygwin build of Python. The regular Win32 Python installation that you
|
||||
can download from <a href="http://www.python.org">python.org</a> will not
|
||||
work with your compiler because the dynamic linking conventions are
|
||||
different (you can use <a href="http://www.mingw.org/">MinGW</a> GCC if
|
||||
you want to build extension modules which are compatible with a stock
|
||||
Win32 Python). The Cygwin installer may be able to install an appropriate
|
||||
version of Python, or you can follow the traditional <a href=
|
||||
"http://www.python.org/download/download_source.html">Unix installation
|
||||
process</a> to build Python from source.</p>
|
||||
|
||||
<p>The special build configuration variables listed <a href=
|
||||
"#cygwin_configuration">above</a> make it possible to use a regular Win32
|
||||
build of bjam to build and test Boost.Python and Boost.Python extensions
|
||||
using Cygwin GCC and targeting a Cygwin build of Python.</p>
|
||||
|
||||
<h3><a name="mingw">Notes for MinGW (and Cygwin with -mno-cygwin) GCC
|
||||
Users</a></h3>
|
||||
|
||||
<p>You will need to create a MinGW-compatible version of the Python
|
||||
library; the one shipped with Python will only work with a
|
||||
Microsoft-compatible linker. Follow the instructions in the
|
||||
"Non-Microsoft" section of the "Building Extensions: Tips And Tricks"
|
||||
chapter in <a href=
|
||||
"http://www.python.org/doc/current/inst/index.html">Installing Python
|
||||
Modules</a> to create <code>libpythonXX.a</code>, where <code>XX</code>
|
||||
corresponds to the major and minor version numbers of your Python
|
||||
installation.</p>
|
||||
|
||||
<h3><a name="results">Results</a></h3>
|
||||
|
||||
<p>The build process will create a
|
||||
<code>libs/python/build/bin-stage</code> subdirectory of the boost root
|
||||
(or of <code>$(ALL_LOCATE_TARGET)</code>, if you have set that variable),
|
||||
containing the built libraries. The libraries are actually built to
|
||||
unique directories for each toolset and variant elsewhere in the
|
||||
filesystem, and copied to the <code>bin-stage</code> directory as a
|
||||
convenience, so if you build with multiple toolsets at once, the product
|
||||
of later toolsets will overwrite that of earlier toolsets in
|
||||
<code>bin-stage</code>.</p>
|
||||
|
||||
<h3><a name="testing">Testing</a></h3>
|
||||
|
||||
<p>To build and test Boost.Python, start from the
|
||||
<code>libs/python/test</code> directory and invoke</p>
|
||||
|
||||
<blockquote>
|
||||
<pre>
|
||||
bjam -sTOOLS=<i><a href=
|
||||
"../../../tools/build/index.html#Tools">toolset</a></i> test
|
||||
</pre>
|
||||
</blockquote>
|
||||
This will update all of the Boost.Python v1 test and example targets. The
|
||||
tests are relatively quiet by default. To get more-verbose output, you
|
||||
might try
|
||||
|
||||
<blockquote>
|
||||
<pre>
|
||||
bjam -sTOOLS=<i><a href=
|
||||
"../../../tools/build/index.html#Tools">toolset</a></i> -sPYTHON_TEST_ARGS=-v test
|
||||
</pre>
|
||||
</blockquote>
|
||||
which will print each test's Python code with the expected output as it
|
||||
passes.
|
||||
|
||||
<h2><a name="building_ext">Building your Extension Module</a></h2>
|
||||
Though there are other approaches, the smoothest and most reliable
|
||||
way to build an extension module using Boost.Python is with
|
||||
Boost.Build. If you have to use another build system, you should
|
||||
use Boost.Build at least once with the
|
||||
"<code><b>-n</b></code>" option so you can see the command-lines it uses,
|
||||
and replicate them. You are likely to run into compilation or linking
|
||||
problems otherwise.
|
||||
|
||||
The <code><a href="../example">libs/python/example</a></code>
|
||||
subdirectory of your boost installation contains a small example
|
||||
which builds and tests two extensions. To build your own
|
||||
extensions copy the example subproject and make the following two edits:
|
||||
|
||||
<ol>
|
||||
<li><code><a
|
||||
href="../example/boost-build.jam"><b>boost-build.jam</b></a></code> -
|
||||
edit the line which reads
|
||||
|
||||
<blockquote>
|
||||
<pre>
|
||||
boost-build ../../../tools/build ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
|
||||
so that the path refers to the <code>tools/build</code> subdirectory
|
||||
of your Boost installation.
|
||||
|
||||
|
||||
<li><code><a href="../example/Jamrules"><b>Jamrules</b></a></code> -
|
||||
edit the line which reads
|
||||
|
||||
<blockquote>
|
||||
<pre>
|
||||
path-global BOOST_ROOT : ../../.. ;
|
||||
</pre>
|
||||
</blockquote>
|
||||
so that the path refers to the root directory of your Boost installation.
|
||||
</ol>
|
||||
|
||||
<p>
|
||||
The instructions <a href="#testing">above</a> for testing Boost.Python
|
||||
apply equally to your new extension modules in this subproject.
|
||||
|
||||
<h2><a name="variants">Build Variants</a></h2>
|
||||
Three <a href=
|
||||
"../../../tools/build/build_system.htm#variants">variant</a>
|
||||
configurations of all python-related targets are supported, and can be
|
||||
selected by setting the <code><a href=
|
||||
"../../../tools/build/build_system.htm#user_globals">BUILD</a></code>
|
||||
variable:
|
||||
|
||||
<ul>
|
||||
<li><code>release</code> (optimization, <tt>-DNDEBUG</tt>)</li>
|
||||
|
||||
<li><code>debug</code> (no optimization <tt>-D_DEBUG</tt>)</li>
|
||||
|
||||
<li><code>debug-python</code> (no optimization, <tt>-D_DEBUG
|
||||
-DBOOST_DEBUG_PYTHON</tt>)</li>
|
||||
</ul>
|
||||
|
||||
<p>The first two variants of the <code>boost_python</code> library are
|
||||
built by default, and are compatible with the default Python
|
||||
distribution. The <code>debug-python</code> variant corresponds to a
|
||||
specially-built debugging version of Python. On Unix platforms, this
|
||||
python is built by adding <code>--with-pydebug</code> when configuring
|
||||
the Python build. On Windows, the debugging version of Python is
|
||||
generated by the "Win32 Debug" target of the <code>PCBuild.dsw</code>
|
||||
Visual C++ 6.0 project in the <code>PCBuild</code> subdirectory of your
|
||||
Python distribution. Extension modules built with Python debugging
|
||||
enabled are <b>not link-compatible</b> with a non-debug build of Python.
|
||||
Since few people actually have a debug build of Python (it doesn't come
|
||||
with the standard distribution), the normal <code>debug</code> variant
|
||||
builds modules which are compatible with ordinary Python.</p>
|
||||
|
||||
<p>On many windows compilers, when extension modules are built with
|
||||
<tt>-D_DEBUG</tt>, Python defaults to <i>force</i> linking with a special
|
||||
debugging version of the Python DLL. Since this debug DLL isn't supplied
|
||||
with the default Python installation for Windows, Boost.Python uses
|
||||
<tt><a href=
|
||||
"../../../boost/python/detail/wrap_python.hpp">boost/python/detail/wrap_python.hpp</a></tt>
|
||||
to temporarily undefine <tt>_DEBUG</tt> when <tt>Python.h</tt> is
|
||||
<tt>#include</tt>d - unless <code>BOOST_DEBUG_PYTHON</code> is
|
||||
defined.</p>
|
||||
|
||||
<p>If you want the extra runtime checks available with the debugging
|
||||
version of the library, <tt>#define BOOST_DEBUG_PYTHON</tt> to re-enable
|
||||
python debuggin, and link with the <code>debug-python</code> variant of
|
||||
<tt>boost_python</tt>.</p>
|
||||
|
||||
<p>If you do not <tt>#define BOOST_DEBUG_PYTHON</tt>, be sure that any
|
||||
source files in your extension module <tt>#include <<a href=
|
||||
"../../../boost/python/detail/wrap_python.hpp">boost/python/detail/wrap_python.hpp</a>></tt>
|
||||
instead of the usual <tt>Python.h</tt>, or you will have link
|
||||
incompatibilities.<br>
|
||||
</p>
|
||||
|
||||
<h2><a name="VisualStudio">Building Using the Microsoft Visual Studio
|
||||
IDE</a></h2>
|
||||
|
||||
<p>For the those of you who feel more comfortable in the IDE world, a
|
||||
workspace and project file have been included in the <a href=
|
||||
"../build/VisualStudio">libs/python/build/VisualStudio</a> subdirectory.
|
||||
It builds release and debug versions of the Boost.Python libraries and
|
||||
places them and the same directory as Jamfile build does, though the
|
||||
intermediate object files are placed in a different directory. The files
|
||||
have been created using Microsoft Visual C++ version 6, but they should
|
||||
work for later versions as well. You will need to tell the IDE where to
|
||||
find the Python <code>Include/</code> and <code>Libs/</code> directories.
|
||||
Under <b>Tools>Options>Directories</b>, add an entry for the Python
|
||||
include dir (i.e. <code>c:/Python22/Include</code>), and one for the Lib
|
||||
(i.e. <code>c:/Python/Libs</code>. Make sure it is <code>Libs</code> with
|
||||
an "<code>s</code>" and not just <code>Lib</code>).</p>
|
||||
|
||||
<h3>Using the IDE for your own projects</h3>
|
||||
|
||||
<p>Building your own projects using the IDE is slightly more complicated.
|
||||
Firstly, you need to make sure that the project you create as the right
|
||||
kind. It should be a "Win32 Dynamic-Link Library". The default one that
|
||||
Visual Studio 6 creates needs some modifications: turn on RTTI, and
|
||||
change the debug and release builds to use the respective debug and
|
||||
release Multithreaded DLL versions. You should probably turn off
|
||||
incremental linking too -- I believe it a bit flaky. If you do this, then
|
||||
change the "Debug Info" to "Program Database" to get rid of the Edit and
|
||||
Continue warning.</p>
|
||||
|
||||
<p>You'll need to add the Boost root directory under
|
||||
<b>Tools>Options>Directories</b> to get your code compiling. To
|
||||
make it link, add the above <code>boost_python.dsp</code> file to your
|
||||
workspace, and make your project depend upon it (under
|
||||
<b>Project>Dependencies</b>). You should be able to build now.</p>
|
||||
|
||||
<p>Lastly, go to the <b>Project Settings>Debug</b> Page and add the
|
||||
<code>Python.exe</code> as the executable for the project. Set a startup
|
||||
directory, and make sure that your current project's output dll, the
|
||||
<code>boost_python.dll</code> and the <code>python22.dll</code> are on
|
||||
the current <code>PATH</code>. If you have a python script that tests
|
||||
your dll, then add it in the "Program Arguments". Now, if all went well,
|
||||
you should be able to hit the Run (F5) button, and debug your code.</p>
|
||||
|
||||
<blockquote>
|
||||
<em>The Visual Studio project files are graciously contributed and
|
||||
maintained by <a href="mailto:brett.calcott@paradise.net.nz">Brett
|
||||
Calcott</a></em>.
|
||||
</blockquote>
|
||||
<hr>
|
||||
|
||||
<p>© Copyright David Abrahams 2002. Permission to copy, use, modify,
|
||||
sell and distribute this document is granted provided this copyright
|
||||
notice appears in all copies. This document is provided ``as is'' without
|
||||
express or implied warranty, and with no claim as to its suitability for
|
||||
any purpose.</p>
|
||||
|
||||
<p>Updated: 29 December, 2002 (David Abrahams)</p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
121
doc/index.html
121
doc/index.html
@@ -1,121 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="boost.css">
|
||||
|
||||
<title>Boost.Python</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center">Boost.Python</h1>
|
||||
|
||||
<h2 align="center">Index</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Synopsis</h2>
|
||||
Welcome to version 2 of <b>Boost.Python</b>, a C++ library which enables
|
||||
seamless interoperability between C++ and the <a href=
|
||||
"http://www.python.org">Python</a> programming language. The new version
|
||||
has been rewritten from the ground up, with a more convenient and
|
||||
flexible interface, and many new capabilities, including support for:
|
||||
|
||||
<ul>
|
||||
<li>References and Pointers</li>
|
||||
|
||||
<li>Globally Registered Type Coercions</li>
|
||||
|
||||
<li>Automatic Cross-Module Type Conversions</li>
|
||||
|
||||
<li>Efficient Function Overloading</li>
|
||||
|
||||
<li>C++ to Python Exception Translation</li>
|
||||
|
||||
<li>Default Arguments</li>
|
||||
|
||||
<li>Keyword Arguments</li>
|
||||
|
||||
<li>Manipulating Python objects in C++</li>
|
||||
|
||||
<li>Exporting C++ Iterators as Python Iterators</li>
|
||||
|
||||
<li>Documentation Strings</li>
|
||||
</ul>
|
||||
The development of these features was funded in part by grants to <a
|
||||
href="http://www.boost-consulting.com">Boost Consulting</a> from the <a
|
||||
href="http://www.llnl.gov/">Lawrence Livermore National Laboratories</a>
|
||||
and by the <a href="http://cci.lbl.gov/">Computational Crystallography
|
||||
Initiative</a> at Lawrence Berkeley National Laboratories.
|
||||
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="index">
|
||||
<dt><a href="tutorial/index.html">Tutorial Introduction</a></dt>
|
||||
|
||||
<dt><a href="building.html">Building and Testing</a></dt>
|
||||
|
||||
<dt><a href="v2/reference.html">Reference Manual</a></dt>
|
||||
|
||||
<dt><a href="v2/configuration.html">Configuration Information</a></dt>
|
||||
|
||||
<dt><a href="v2/platforms.html">Known Working Platforms and
|
||||
Compilers</a></dt>
|
||||
|
||||
<dt><a href="v2/definitions.html">Definitions</a></dt>
|
||||
|
||||
<dt><a href="projects.html">Projects using Boost.Python</a></dt>
|
||||
|
||||
<dt><a href="support.html">Support Resources</a></dt>
|
||||
|
||||
<dt><a href="v2/faq.html">Frequently Asked Questions (FAQs)</a></dt>
|
||||
|
||||
<dt><a href="../pyste/index.html">Pyste (Boost.Python code generator)</a></dt>
|
||||
|
||||
<dt><a href="internals.html">Internals Documentation</a></dt>
|
||||
|
||||
<dt><a href="news.html">News/Change Log</a></dt>
|
||||
|
||||
<dt><a href="../todo.html">TODO list</a></dt>
|
||||
|
||||
<dt><a href="v2/progress_reports.html">LLNL Progress Reports</a></dt>
|
||||
|
||||
<dt><a href="v2/acknowledgments.html">Acknowledgments</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2>Articles</h2>
|
||||
|
||||
"<a href="PyConDC_2003/bpl.html">Building Hybrid
|
||||
Systems With Boost Python</a>", by Dave Abrahams and Ralf
|
||||
W. Grosse-Kunstleve (<a href="PyConDC_2003/bpl.pdf">PDF</a>)
|
||||
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
26 August, 2003
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href="../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002-2003. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,186 +0,0 @@
|
||||
<?xml version="1.0" encoding="utf-8" ?>
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||||
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
||||
<meta name="generator" content="Docutils 0.3.0: http://docutils.sourceforge.net/" />
|
||||
<title>Boost.Python Internals Boost</title>
|
||||
<link rel="stylesheet" href="../../../rst.css" type="text/css" />
|
||||
</head>
|
||||
<body>
|
||||
<div class="document" id="boost-python-internals-logo">
|
||||
<h1 class="title"><a class="reference" href="index.html">Boost.Python</a> Internals <a class="reference" href="../../../index.htm"><img alt="Boost" src="../../../c++boost.gif" /></a></h1>
|
||||
<div class="section" id="a-conversation-between-brett-calcott-and-david-abrahams">
|
||||
<h1><a name="a-conversation-between-brett-calcott-and-david-abrahams">A conversation between Brett Calcott and David Abrahams</a></h1>
|
||||
<table class="field-list" frame="void" rules="none">
|
||||
<col class="field-name" />
|
||||
<col class="field-body" />
|
||||
<tbody valign="top">
|
||||
<tr class="field"><th class="field-name">copyright:</th><td class="field-body">Copyright David Abrahams and Brett Calcott 2003. See
|
||||
accompanying <a class="reference" href="../../../LICENSE">license</a> for terms of use.</td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
<p>In both of these cases, I'm quite capable of reading code - but the
|
||||
thing I don't get from scanning the source is a sense of the
|
||||
architecture, both structurally, and temporally (er, I mean in what
|
||||
order things go on).</p>
|
||||
<ol class="arabic">
|
||||
<li><p class="first">What happens when you do the following:</p>
|
||||
<pre class="literal-block">
|
||||
struct boring {};
|
||||
...etc...
|
||||
class_<boring>("boring")
|
||||
;
|
||||
</pre>
|
||||
</li>
|
||||
</ol>
|
||||
<p>There seems to be a fair bit going on.</p>
|
||||
<blockquote>
|
||||
<ul class="simple">
|
||||
<li>Python needs a new ClassType to be registered.</li>
|
||||
<li>We need to construct a new type that can hold our boring struct.</li>
|
||||
<li>Inward and outward converters need to be registered for the type.</li>
|
||||
</ul>
|
||||
</blockquote>
|
||||
<p>Can you gesture in the general direction where these things are done?</p>
|
||||
<blockquote>
|
||||
<p>I only have time for a "off-the-top-of-my-head" answer at the moment;
|
||||
I suggest you step through the code with a debugger after reading this
|
||||
to see how it works, fill in details, and make sure I didn't forget
|
||||
anything.</p>
|
||||
<blockquote>
|
||||
<p>A new (Python) subclass of Boost.Python.Instance (see
|
||||
libs/python/src/object/class.cpp) is created by invoking
|
||||
Boost.Python.class, the metatype:</p>
|
||||
<pre class="literal-block">
|
||||
>>> boring = Boost.Python.class(
|
||||
... 'boring'
|
||||
... , bases_tuple # in this case, just ()
|
||||
... , {
|
||||
... '__module__' : module_name
|
||||
... , '__doc__' : doc_string # optional
|
||||
... }
|
||||
... )
|
||||
</pre>
|
||||
<p>A handle to this object is stuck in the m_class_object field
|
||||
of the registration associated with <tt class="literal"><span class="pre">typeid(boring)</span></tt>. The
|
||||
registry will keep that object alive forever, even if you
|
||||
wipe out the 'boring' attribute of the extension module
|
||||
(probably not a good thing).</p>
|
||||
<p>Because you didn't specify <tt class="literal"><span class="pre">class<boring,</span> <span class="pre">non_copyable,</span>
|
||||
<span class="pre">...></span></tt>, a to-python converter for boring is registered which
|
||||
copies its argument into a value_holder held by the the
|
||||
Python boring object.</p>
|
||||
<p>Because you didn't specify <tt class="literal"><span class="pre">class<boring</span> <span class="pre">...>(no_init)</span></tt>,
|
||||
an <tt class="literal"><span class="pre">__init__</span></tt> function object is added to the class
|
||||
dictionary which default-constructs a boring in a
|
||||
value_holder (because you didn't specify some smart pointer
|
||||
or derived wrapper class as a holder) held by the Python
|
||||
boring object.</p>
|
||||
<p><tt class="literal"><span class="pre">register_class_from_python</span></tt> is used to register a
|
||||
from-python converter for <tt class="literal"><span class="pre">shared_ptr<boring></span></tt>.
|
||||
<tt class="literal"><span class="pre">boost::shared_ptr</span></tt>s are special among smart pointers
|
||||
because their Deleter argument can be made to manage the
|
||||
whole Python object, not just the C++ object it contains, no
|
||||
matter how the C++ object is held.</p>
|
||||
<p>If there were any <tt class="literal"><span class="pre">bases<></span></tt>, we'd also be registering the
|
||||
relationship between these base classes and boring in the
|
||||
up/down cast graph (<tt class="literal"><span class="pre">inheritance.[hpp/cpp]</span></tt>).</p>
|
||||
<p>In earlier versions of the code, we'd be registering lvalue
|
||||
from-python converters for the class here, but now
|
||||
from-python conversion for wrapped classes is handled as a
|
||||
special case, before consulting the registry, if the source
|
||||
Python object's metaclass is the Boost.Python metaclass.</p>
|
||||
<p>Hmm, that from-python converter probably ought to be handled
|
||||
the way class converters are, with no explicit conversions
|
||||
registered.</p>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
<ol class="arabic" start="2">
|
||||
<li><p class="first">Can you give a brief overview of the data structures that are
|
||||
present in the registry</p>
|
||||
<blockquote>
|
||||
<p>The registry is simple: it's just a map from typeid ->
|
||||
registration (see boost/python/converter/registrations.hpp).
|
||||
<tt class="literal"><span class="pre">lvalue_chain</span></tt> and <tt class="literal"><span class="pre">rvalue_chain</span></tt> are simple endogenous
|
||||
linked lists.</p>
|
||||
<p>If you want to know more, just ask.</p>
|
||||
<p>If you want to know about the cast graph, ask me something specific in
|
||||
a separate message.</p>
|
||||
</blockquote>
|
||||
<p>and an overview of the process that happens as a type makes its
|
||||
way from c++ to python and back again.</p>
|
||||
</li>
|
||||
</ol>
|
||||
<blockquote>
|
||||
<p>Big subject. I suggest some background reading: look for relevant
|
||||
info in the LLNL progress reports and the messages they link to.
|
||||
Also,</p>
|
||||
<blockquote>
|
||||
<p><a class="reference" href="http://mail.python.org/pipermail/c++-sig/2002-May/001023.html">http://mail.python.org/pipermail/c++-sig/2002-May/001023.html</a></p>
|
||||
<p><a class="reference" href="http://mail.python.org/pipermail/c++-sig/2002-December/003115.html">http://mail.python.org/pipermail/c++-sig/2002-December/003115.html</a></p>
|
||||
<p><a class="reference" href="http://aspn.activestate.com/ASPN/Mail/Message/1280898">http://aspn.activestate.com/ASPN/Mail/Message/1280898</a></p>
|
||||
<p><a class="reference" href="http://mail.python.org/pipermail/c++-sig/2002-July/001755.html">http://mail.python.org/pipermail/c++-sig/2002-July/001755.html</a></p>
|
||||
</blockquote>
|
||||
<p>from c++ to python:</p>
|
||||
<blockquote>
|
||||
<p>It depends on the type and the call policies in use or, for
|
||||
<tt class="literal"><span class="pre">call<>(...)</span></tt>, <tt class="literal"><span class="pre">call_method<>(...)</span></tt>, or <tt class="literal"><span class="pre">object(...)</span></tt>, if
|
||||
<tt class="literal"><span class="pre">ref</span></tt> or <tt class="literal"><span class="pre">ptr</span></tt> is used. There are also two basic
|
||||
categories to to-python conversion, "return value" conversion
|
||||
(for Python->C++ calls) and "argument" conversion (for
|
||||
C++->Python calls and explicit <tt class="literal"><span class="pre">object()</span></tt> conversions). The
|
||||
behavior of these two categories differs subtly in various ways
|
||||
whose details I forget at the moment. You can probably find
|
||||
the answers in the above references, and certainly in the code.</p>
|
||||
<p>The "default" case is by-value (copying) conversion, which uses
|
||||
to_python_value as a to-python converter.</p>
|
||||
<blockquote>
|
||||
<p>Since there can sensibly be only one way to convert any type
|
||||
to python (disregarding the idea of scoped registries for the
|
||||
moment), it makes sense that to-python conversions can be
|
||||
handled by specializing a template. If the type is one of
|
||||
the types handled by a built-in conversion
|
||||
(builtin_converters.hpp), the corresponding template
|
||||
specialization of to_python_value gets used.</p>
|
||||
<p>Otherwise, to_python_value uses the <tt class="literal"><span class="pre">m_to_python</span></tt>
|
||||
function in the registration for the C++ type.</p>
|
||||
</blockquote>
|
||||
<p>Other conversions, like by-reference conversions, are only
|
||||
available for wrapped classes, and are requested explicitly by
|
||||
using <tt class="literal"><span class="pre">ref(...)</span></tt>, <tt class="literal"><span class="pre">ptr(...)</span></tt>, or by specifying different
|
||||
CallPolicies for a call, which can cause a different to-python
|
||||
converter to be used. These conversions are never registered
|
||||
anywhere, though they do need to use the registration to find
|
||||
the Python class corresponding to the C++ type being referred
|
||||
to. They just build a new Python instance and stick the
|
||||
appropriate Holder instance in it.</p>
|
||||
</blockquote>
|
||||
<p>from python to C++:</p>
|
||||
<blockquote>
|
||||
<p>Once again I think there is a distinction between "return value"
|
||||
and "argument" conversions, and I forget exactly what that is.</p>
|
||||
<p>What happens depends on whether an lvalue conversion is needed
|
||||
(see <a class="reference" href="http://mail.python.org/pipermail/c++-sig/2002-May/001023.html">http://mail.python.org/pipermail/c++-sig/2002-May/001023.html</a>)
|
||||
All lvalue conversions are also registered in a type's rvalue
|
||||
conversion chain, since when an rvalue will do, an lvalue is
|
||||
certainly good enough.</p>
|
||||
<p>An lvalue conversion can be done in one step (just get me the
|
||||
pointer to the object - it can be <tt class="literal"><span class="pre">NULL</span></tt> if no conversion is
|
||||
possible) while an rvalue conversion requires two steps to
|
||||
support wrapped function overloading and multiple converters for
|
||||
a given C++ target type: first tell me if a conversion is
|
||||
possible, then construct the converted object as a second step.</p>
|
||||
</blockquote>
|
||||
</blockquote>
|
||||
</div>
|
||||
</div>
|
||||
<hr class="footer"/>
|
||||
<div class="footer">
|
||||
<a class="reference" href="internals.rst">View document source</a>.
|
||||
Generated on: 2003-09-12 14:51 UTC.
|
||||
Generated by <a class="reference" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
|
||||
</div>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,181 +0,0 @@
|
||||
===================================
|
||||
Boost.Python_ Internals |(logo)|__
|
||||
===================================
|
||||
|
||||
.. |(logo)| image:: ../../../c++boost.gif
|
||||
:alt: Boost
|
||||
|
||||
__ ../../../index.htm
|
||||
|
||||
.. _`Boost.Python`: index.html
|
||||
|
||||
.. _license: ../../../LICENSE
|
||||
|
||||
|
||||
-------------------------------------------------------
|
||||
A conversation between Brett Calcott and David Abrahams
|
||||
-------------------------------------------------------
|
||||
|
||||
:copyright: Copyright David Abrahams and Brett Calcott 2003. See
|
||||
accompanying license_ for terms of use.
|
||||
|
||||
In both of these cases, I'm quite capable of reading code - but the
|
||||
thing I don't get from scanning the source is a sense of the
|
||||
architecture, both structurally, and temporally (er, I mean in what
|
||||
order things go on).
|
||||
|
||||
1) What happens when you do the following::
|
||||
|
||||
struct boring {};
|
||||
...etc...
|
||||
class_<boring>("boring")
|
||||
;
|
||||
|
||||
There seems to be a fair bit going on.
|
||||
|
||||
- Python needs a new ClassType to be registered.
|
||||
- We need to construct a new type that can hold our boring struct.
|
||||
- Inward and outward converters need to be registered for the type.
|
||||
|
||||
Can you gesture in the general direction where these things are done?
|
||||
|
||||
I only have time for a "off-the-top-of-my-head" answer at the moment;
|
||||
I suggest you step through the code with a debugger after reading this
|
||||
to see how it works, fill in details, and make sure I didn't forget
|
||||
anything.
|
||||
|
||||
A new (Python) subclass of Boost.Python.Instance (see
|
||||
libs/python/src/object/class.cpp) is created by invoking
|
||||
Boost.Python.class, the metatype::
|
||||
|
||||
>>> boring = Boost.Python.class(
|
||||
... 'boring'
|
||||
... , bases_tuple # in this case, just ()
|
||||
... , {
|
||||
... '__module__' : module_name
|
||||
... , '__doc__' : doc_string # optional
|
||||
... }
|
||||
... )
|
||||
|
||||
A handle to this object is stuck in the m_class_object field
|
||||
of the registration associated with ``typeid(boring)``. The
|
||||
registry will keep that object alive forever, even if you
|
||||
wipe out the 'boring' attribute of the extension module
|
||||
(probably not a good thing).
|
||||
|
||||
Because you didn't specify ``class<boring, non_copyable,
|
||||
...>``, a to-python converter for boring is registered which
|
||||
copies its argument into a value_holder held by the the
|
||||
Python boring object.
|
||||
|
||||
Because you didn't specify ``class<boring ...>(no_init)``,
|
||||
an ``__init__`` function object is added to the class
|
||||
dictionary which default-constructs a boring in a
|
||||
value_holder (because you didn't specify some smart pointer
|
||||
or derived wrapper class as a holder) held by the Python
|
||||
boring object.
|
||||
|
||||
``register_class_from_python`` is used to register a
|
||||
from-python converter for ``shared_ptr<boring>``.
|
||||
``boost::shared_ptr``\ s are special among smart pointers
|
||||
because their Deleter argument can be made to manage the
|
||||
whole Python object, not just the C++ object it contains, no
|
||||
matter how the C++ object is held.
|
||||
|
||||
If there were any ``bases<>``, we'd also be registering the
|
||||
relationship between these base classes and boring in the
|
||||
up/down cast graph (``inheritance.[hpp/cpp]``).
|
||||
|
||||
In earlier versions of the code, we'd be registering lvalue
|
||||
from-python converters for the class here, but now
|
||||
from-python conversion for wrapped classes is handled as a
|
||||
special case, before consulting the registry, if the source
|
||||
Python object's metaclass is the Boost.Python metaclass.
|
||||
|
||||
Hmm, that from-python converter probably ought to be handled
|
||||
the way class converters are, with no explicit conversions
|
||||
registered.
|
||||
|
||||
2) Can you give a brief overview of the data structures that are
|
||||
present in the registry
|
||||
|
||||
The registry is simple: it's just a map from typeid ->
|
||||
registration (see boost/python/converter/registrations.hpp).
|
||||
``lvalue_chain`` and ``rvalue_chain`` are simple endogenous
|
||||
linked lists.
|
||||
|
||||
If you want to know more, just ask.
|
||||
|
||||
If you want to know about the cast graph, ask me something specific in
|
||||
a separate message.
|
||||
|
||||
and an overview of the process that happens as a type makes its
|
||||
way from c++ to python and back again.
|
||||
|
||||
Big subject. I suggest some background reading: look for relevant
|
||||
info in the LLNL progress reports and the messages they link to.
|
||||
Also,
|
||||
|
||||
http://mail.python.org/pipermail/c++-sig/2002-May/001023.html
|
||||
|
||||
http://mail.python.org/pipermail/c++-sig/2002-December/003115.html
|
||||
|
||||
http://aspn.activestate.com/ASPN/Mail/Message/1280898
|
||||
|
||||
http://mail.python.org/pipermail/c++-sig/2002-July/001755.html
|
||||
|
||||
from c++ to python:
|
||||
|
||||
It depends on the type and the call policies in use or, for
|
||||
``call<>(...)``, ``call_method<>(...)``, or ``object(...)``, if
|
||||
``ref`` or ``ptr`` is used. There are also two basic
|
||||
categories to to-python conversion, "return value" conversion
|
||||
(for Python->C++ calls) and "argument" conversion (for
|
||||
C++->Python calls and explicit ``object()`` conversions). The
|
||||
behavior of these two categories differs subtly in various ways
|
||||
whose details I forget at the moment. You can probably find
|
||||
the answers in the above references, and certainly in the code.
|
||||
|
||||
The "default" case is by-value (copying) conversion, which uses
|
||||
to_python_value as a to-python converter.
|
||||
|
||||
Since there can sensibly be only one way to convert any type
|
||||
to python (disregarding the idea of scoped registries for the
|
||||
moment), it makes sense that to-python conversions can be
|
||||
handled by specializing a template. If the type is one of
|
||||
the types handled by a built-in conversion
|
||||
(builtin_converters.hpp), the corresponding template
|
||||
specialization of to_python_value gets used.
|
||||
|
||||
Otherwise, to_python_value uses the ``m_to_python``
|
||||
function in the registration for the C++ type.
|
||||
|
||||
Other conversions, like by-reference conversions, are only
|
||||
available for wrapped classes, and are requested explicitly by
|
||||
using ``ref(...)``, ``ptr(...)``, or by specifying different
|
||||
CallPolicies for a call, which can cause a different to-python
|
||||
converter to be used. These conversions are never registered
|
||||
anywhere, though they do need to use the registration to find
|
||||
the Python class corresponding to the C++ type being referred
|
||||
to. They just build a new Python instance and stick the
|
||||
appropriate Holder instance in it.
|
||||
|
||||
|
||||
from python to C++:
|
||||
|
||||
Once again I think there is a distinction between "return value"
|
||||
and "argument" conversions, and I forget exactly what that is.
|
||||
|
||||
What happens depends on whether an lvalue conversion is needed
|
||||
(see http://mail.python.org/pipermail/c++-sig/2002-May/001023.html)
|
||||
All lvalue conversions are also registered in a type's rvalue
|
||||
conversion chain, since when an rvalue will do, an lvalue is
|
||||
certainly good enough.
|
||||
|
||||
An lvalue conversion can be done in one step (just get me the
|
||||
pointer to the object - it can be ``NULL`` if no conversion is
|
||||
possible) while an rvalue conversion requires two steps to
|
||||
support wrapped function overloading and multiple converters for
|
||||
a given C++ target type: first tell me if a conversion is
|
||||
possible, then construct the converted object as a second step.
|
||||
|
||||
@@ -1,328 +0,0 @@
|
||||
<html>
|
||||
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
|
||||
<title>A New Type Conversion Mechanism for Boost.Python</title>
|
||||
</head>
|
||||
|
||||
<body bgcolor="#FFFFFF" text="#000000">
|
||||
|
||||
<p><img border="0" src="../../../c++boost.gif" width="277" height="86"
|
||||
alt="boost logo"></p>
|
||||
|
||||
<h1>A New Type Conversion Mechanism for Boost.Python</h1>
|
||||
|
||||
<p>By <a href="../../../people/dave_abrahams.htm">David Abrahams</a>.
|
||||
|
||||
<h2>Introduction</h2>
|
||||
|
||||
This document describes a redesign of the mechanism for automatically
|
||||
converting objects between C++ and Python. The current implementation
|
||||
uses two functions for any type <tt>T</tt>:
|
||||
|
||||
<blockquote><pre>
|
||||
U from_python(PyObject*, type<T>);
|
||||
void to_python(V);
|
||||
</pre></blockquote>
|
||||
|
||||
where U is convertible to T and T is convertible to V. These functions
|
||||
are at the heart of C++/Python interoperability in Boost.Python, so
|
||||
why would we want to change them? There are many reasons:
|
||||
|
||||
<h3>Bugs</h3>
|
||||
<p>Firstly, the current mechanism relies on a common C++ compiler
|
||||
bug. This is not just embarrassing: as compilers get to be more
|
||||
conformant, the library stops working. The issue, in detail, is the
|
||||
use of inline friend functions in templates to generate
|
||||
conversions. It is a very powerful, and legal technique as long as
|
||||
it's used correctly:
|
||||
|
||||
<blockquote><pre>
|
||||
template <class Derived>
|
||||
struct add_some_functions
|
||||
{
|
||||
friend <i>return-type</i> some_function1(..., Derived <i>cv-*-&-opt</i>, ...);
|
||||
friend <i>return-type</i> some_function2(..., Derived <i>cv-*-&-opt</i>, ...);
|
||||
};
|
||||
|
||||
template <class T>
|
||||
struct some_template : add_some_functions<some_template<T> >
|
||||
{
|
||||
};
|
||||
</pre></blockquote>
|
||||
|
||||
The <tt>add_some_functions</tt> template generates free functions
|
||||
which operate on <tt>Derived</tt>, or on related types. Strictly
|
||||
speaking the related types are not just cv-qualified <tt>Derived</tt>
|
||||
values, pointers and/or references. Section 3.4.2 in the standard
|
||||
describes exactly which types you must use as parameters to these
|
||||
functions if you want the functions to be found
|
||||
(there is also a less-technical description in section 11.5.1 of
|
||||
C++PL3 <a href="#ref_1">[1]</a>). Suffice it to say that
|
||||
with the current design, the <tt>from_python</tt> and
|
||||
<tt>to_python</tt> functions are not supposed to be callable under any
|
||||
conditions!
|
||||
|
||||
<h3>Compilation and Linking Time</h3>
|
||||
|
||||
The conversion functions generated for each wrapped class using the
|
||||
above technique are not function templates, but regular functions. The
|
||||
upshot is that they must <i>all</i> be generated regardless of whether
|
||||
they are actually used. Generating all of those functions can slow
|
||||
down module compilation, and resolving the references can slow down
|
||||
linking.
|
||||
|
||||
<h3>Efficiency</h3>
|
||||
|
||||
The conversion functions are primarily used in (member) function
|
||||
wrappers to convert the arguments and return values. Being functions,
|
||||
converters have no interface which allows us to ask "will the
|
||||
conversion succeed?" without calling the function. Since the
|
||||
return value of the function must be the object to be passed as an
|
||||
argument, Boost.Python currently uses C++ exception-handling to detect
|
||||
an unsuccessful conversion. It's not a particularly good use of
|
||||
exception-handling, since the failure is not handled very far from
|
||||
where it occurred. More importantly, it means that C++ exceptions are
|
||||
thrown during overload resolution as we seek an overload that matches
|
||||
the arguments passed. Depending on the implementation, this approach
|
||||
can result in significant slowdowns.
|
||||
|
||||
<p>It is also unclear that the current library generates a minimal
|
||||
amount of code for any type conversion. Many of the conversion
|
||||
functions are nontrivial, and partly because of compiler limitations,
|
||||
they are declared <tt>inline</tt>. Also, we could have done a better
|
||||
job separating the type-specific conversion code from the code which
|
||||
is type-independent.
|
||||
|
||||
<h3>Cross-module Support</h3>
|
||||
|
||||
The current strategy requires every module to contain the definition
|
||||
of conversions it uses. In general, a new module can never supply
|
||||
conversion code which is used by another module. Ralf Grosse-Kunstleve
|
||||
designed a clever system which imports conversions directly from one
|
||||
library into another using some explicit declarations, but it has some
|
||||
disadvantages also:
|
||||
|
||||
<ol>
|
||||
<li>The system Ullrich Koethe designed for implicit conversion between
|
||||
wrapped classes related through inheritance does not currently work if
|
||||
the classes are defined in separate modules.
|
||||
|
||||
<li>The writer of the importing module is required to know the name of
|
||||
the module supplying the imported conversions.
|
||||
|
||||
<li>There can be only one way to extract any given C++ type from a
|
||||
Python object in a given module.
|
||||
</ol>
|
||||
|
||||
The first item might be addressed by moving Boost.Python into a shared
|
||||
library, but the other two cannot. Ralf turned the limitation in item
|
||||
two into a feature: the required module is loaded implicitly when a
|
||||
conversion it defines is invoked. We will probably want to provide
|
||||
that functionality anyway, but it's not clear that we should require
|
||||
the declaration of all such conversions. The final item is a more
|
||||
serious limitation. If, for example, new numeric types are defined in
|
||||
separate modules, and these types can all be converted to
|
||||
<tt>double</tt>s, we have to choose just one conversion method.
|
||||
|
||||
<h3>Ease-of-use</h3>
|
||||
|
||||
One persistent source of confusion for users of Boost.Python has been
|
||||
the fact that conversions for a class are not be visible at
|
||||
compile-time until the declaration of that class has been seen. When
|
||||
the user tries to expose a (member) function operating on or returning
|
||||
an instance of the class in question, compilation fails...even though
|
||||
the user goes on to expose the class in the same translation unit!
|
||||
|
||||
<p>
|
||||
The new system lifts all compile-time checks for the existence of
|
||||
particular type conversions and replaces them with runtime checks, in
|
||||
true Pythonic style. While this might seem cavalier, the compile-time
|
||||
checks are actually not much use in the current system if many classes
|
||||
are wrapped in separate modules, since the checks are based only on
|
||||
the user's declaration that the conversions exist.
|
||||
|
||||
<h2>The New Design</h2>
|
||||
|
||||
<h3>Motivation</h3>
|
||||
|
||||
The new design was heavily influenced by a desire to generate as
|
||||
little code as possible in extension modules. Some of Boost.Python's
|
||||
clients are enormous projects where link time is proportional to the
|
||||
amount of object code, and there are many Python extension modules. As
|
||||
such, we try to keep type-specific conversion code out of modules
|
||||
other than the one the converters are defined in, and rely as much as
|
||||
possible on centralized control through a shared library.
|
||||
|
||||
<h3>The Basics</h3>
|
||||
|
||||
The library contains a <tt>registry</tt> which maps runtime type
|
||||
identifiers (actually an extension of <tt>std::type_info</tt> which
|
||||
preserves references and constness) to entries containing type
|
||||
converters. An <tt>entry</tt> can contain only one converter from C++ to Python
|
||||
(<tt>wrapper</tt>), but many converters from Python to C++
|
||||
(<tt>unwrapper</tt>s). <font color="#ff0000">What should happen if
|
||||
multiple modules try to register wrappers for the same type?</font>. Wrappers
|
||||
and unwrappers are known as <tt>body</tt> objects, and are accessed
|
||||
by the user and the library (in its function-wrapping code) through
|
||||
corresponding <tt>handle</tt> (<tt>wrap<T></tt> and
|
||||
<tt>unwrap<T></tt>) objects. The <tt>handle</tt> objects are
|
||||
extremely lightweight, and delegate <i>all</i> of their operations to
|
||||
the corresponding <tt>body</tt>.
|
||||
|
||||
<p>
|
||||
When a <tt>handle</tt> object is constructed, it accesses the
|
||||
registry to find a corresponding <tt>body</tt> that can convert the
|
||||
handle's constructor argument. Actually the registry record for any
|
||||
type
|
||||
<tt>T</tt>used in a module is looked up only once and stored in a
|
||||
static <tt>registration<T></tt> object for efficiency. For
|
||||
example, if the handle is an <tt>unwrap<Foo&></tt> object,
|
||||
the <tt>entry</tt> for <tt>Foo&</tt> is looked up in the
|
||||
<tt>registry</tt>, and each <tt>unwrapper</tt> it contains is queried
|
||||
to determine if it can convert the
|
||||
<tt>PyObject*</tt> with which the <tt>unwrap</tt> was constructed. If
|
||||
a body object which can perform the conversion is found, a pointer to
|
||||
it is stored in the handle. A body object may at any point store
|
||||
additional data in the handle to speed up the conversion process.
|
||||
|
||||
<p>
|
||||
Now that the handle has been constructed, the user can ask it whether
|
||||
the conversion can be performed. All handles can be tested as though
|
||||
they were convertible to <tt>bool</tt>; a <tt>true</tt> value
|
||||
indicates success. If the user forges ahead and tries to do the
|
||||
conversion without checking when no conversion is possible, an
|
||||
exception will be thrown as usual. The conversion itself is performed
|
||||
by the body object.
|
||||
|
||||
<h3>Handling complex conversions</h3>
|
||||
|
||||
<p>Some conversions may require a dynamic allocation. For example,
|
||||
when a Python tuple is converted to a <tt>std::vector<double>
|
||||
const&</tt>, we need some storage into which to construct the
|
||||
vector so that a reference to it can be formed. Furthermore, multiple
|
||||
conversions of the same type may need to be "active"
|
||||
simultaneously, so we can't keep a single copy of the storage
|
||||
anywhere. We could keep the storage in the <tt>body</tt> object, and
|
||||
have the body clone itself in case the storage is used, but in that
|
||||
case the storage in the body which lives in the registry is never
|
||||
used. If the storage was actually an object of the target type (the
|
||||
safest way in C++), we'd have to find a way to construct one for the
|
||||
body in the registry, since it may not have a default constructor.
|
||||
|
||||
<p>
|
||||
The most obvious way out of this quagmire is to allocate the object using a
|
||||
<i>new-expression</i>, and store a pointer to it in the handle. Since
|
||||
the <tt>body</tt> object knows everything about the data it needs to
|
||||
allocate (if any), it is also given responsibility for destroying that
|
||||
data. When the <tt>handle</tt> is destroyed it asks the <tt>body</tt>
|
||||
object to tear down any data it may have stored there. In many ways,
|
||||
you can think of the <tt>body</tt> as a "dynamically-determined
|
||||
vtable" for the handle.
|
||||
|
||||
<h3>Eliminating Redundancy</h3>
|
||||
|
||||
If you look at the current Boost.Python code, you'll see that there
|
||||
are an enormous number of conversion functions generated for each
|
||||
wrapped class. For a given class <tt>T</tt>, functions are generated
|
||||
to extract the following types <tt>from_python</tt>:
|
||||
|
||||
<blockquote><pre>
|
||||
T*
|
||||
T const*
|
||||
T const* const&
|
||||
T* const&
|
||||
T&
|
||||
T const&
|
||||
T
|
||||
std::auto_ptr<T>&
|
||||
std::auto_ptr<T>
|
||||
std::auto_ptr<T> const&
|
||||
boost::shared_ptr<T>&
|
||||
boost::shared_ptr<T>
|
||||
boost::shared_ptr<T> const&
|
||||
</pre></blockquote>
|
||||
|
||||
Most of these are implemented in terms of just a few conversions, and
|
||||
<t>if you're lucky</t>, they will be inlined and cause no extra
|
||||
overhead. In the new system, however, a significant amount of data
|
||||
will be associated with each type that needs to be converted. We
|
||||
certainly don't want to register a separate unwrapper object for all
|
||||
of the above types.
|
||||
|
||||
<p>Fortunately, much of the redundancy can be eliminated. For example,
|
||||
if we generate an unwrapper for <tt>T&</tt>, we don't need an
|
||||
unwrapper for <tt>T const&</tt> or <tt>T</tt>. Accordingly, the user's
|
||||
request to wrap/unwrap a given type is translated at compile-time into
|
||||
a request which helps to eliminate redundancy. The rules used to
|
||||
<tt>unwrap</tt> a type are:
|
||||
|
||||
<ol>
|
||||
<li> Treat built-in types specially: when unwrapping a value or
|
||||
constant reference to one of these, use a value for the target
|
||||
type. It will bind to a const reference if neccessary, and more
|
||||
importantly, avoids having to dynamically allocate room for
|
||||
an lvalue of types which can be cheaply copied.
|
||||
<li>
|
||||
Reduce everything else to a reference to an un-cv-qualified type
|
||||
where possible. Since cv-qualification is lost on Python
|
||||
anyway, there's no point in trying to convert to a
|
||||
<tt>const&</tt>. <font color="#ff0000">What about conversions
|
||||
to values like the tuple->vector example above? It seems to me
|
||||
that we don't want to make a <tt>vector<double>&</tt>
|
||||
(non-const) converter available for that case. We may need to
|
||||
rethink this slightly.</font>
|
||||
</ol>
|
||||
|
||||
<p>To handle the problem described above in item 2, we modify the
|
||||
procedure slightly. To unwrap any non-scalar <tt>T</tt>, we seek an
|
||||
unwrapper for <tt>add_reference<T>::type</tt>. Unwrappers for
|
||||
<tt>T const&</tt> always return <tt>T&</tt>, and are
|
||||
registered under both <tt>T &</tt> and
|
||||
<tt>T const&</tt>.
|
||||
|
||||
<p>For compilers not supporting partial specialization, unwrappers for
|
||||
<tt>T const&</tt> must return <tt>T const&</tt>
|
||||
(since constness can't be stripped), but a separate unwrapper object
|
||||
need to be registered for <tt>T &</tt> and
|
||||
<tt>T const&</tt> anyway, for the same reasons.
|
||||
|
||||
<font color="#ff0000">We may want to make it possible to compile as
|
||||
though partial specialization were unavailable even on compilers where
|
||||
it is available, in case modules could be compiled by different
|
||||
compilers with compatible ABIs (e.g. Intel C++ and MSVC6).</font>
|
||||
|
||||
<h3>Efficient Argument Conversion</h3>
|
||||
|
||||
Since type conversions are primarily used in function wrappers, an
|
||||
optimization is provided for the case where a group of conversions are
|
||||
used together. Each <tt>handle</tt> class has a corresponding
|
||||
"<tt>_more</tt>" class which does the same job, but has a
|
||||
trivial destructor. Instead of asking each "<tt>_more</tt>"
|
||||
handle to destroy its own body, it is linked into an endogenous list
|
||||
managed by the first (ordinary) handle. The <tt>wrap</tt> and
|
||||
<tt>unwrap</tt> destructors are responsible for traversing that list
|
||||
and asking each <tt>body</tt> class to tear down its
|
||||
<tt>handle</tt>. This mechanism is also used to determine if all of
|
||||
the argument/return-value conversions can succeed with a single
|
||||
function call in the function wrapping code. <font color="#ff0000">We
|
||||
might need to handle return values in a separate step for Python
|
||||
callbacks, since the availablility of a conversion won't be known
|
||||
until the result object is retrieved.</font>
|
||||
|
||||
<br>
|
||||
<hr>
|
||||
<h2>References</h2>
|
||||
|
||||
<p><a name="ref_1">[1]</a>B. Stroustrup, The C++ Programming Language
|
||||
Special Edition Addison-Wesley, ISBN 0-201-70073-5.
|
||||
|
||||
<hr>
|
||||
<p>Revised <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="31283" --></p>
|
||||
<p>© Copyright David Abrahams, 2001</p>
|
||||
|
||||
</body>
|
||||
|
||||
</html>
|
||||
@@ -1,111 +0,0 @@
|
||||
This hierarchy contains converter handle classes.
|
||||
|
||||
|
||||
+-------------+
|
||||
| noncopyable |
|
||||
+-------------+
|
||||
^
|
||||
| A common base class used so that
|
||||
+--------+--------+ conversions can be linked into a
|
||||
| conversion_base | chain for efficient argument
|
||||
+-----------------+ conversion
|
||||
^
|
||||
|
|
||||
+---------+-----------+
|
||||
| |
|
||||
+-----------+----+ +------+-------+ only used for
|
||||
| unwrap_more<T> | | wrap_more<T> | chaining, and don't manage any
|
||||
+----------------+ +--------------+ resources.
|
||||
^ ^
|
||||
| |
|
||||
+-----+-----+ +-------+-+ These converters are what users
|
||||
| unwrap<T> | | wrap<T> | actually touch, but they do so
|
||||
+-----------+ +---------+ through a type generator which
|
||||
minimizes the number of converters
|
||||
that must be generated, so they
|
||||
|
||||
|
||||
Each unwrap<T>, unwrap_more<T>, wrap<T>, wrap_more<T> converter holds
|
||||
a reference to an appropriate converter object
|
||||
|
||||
This hierarchy contains converter body classes
|
||||
|
||||
Exposes use/release which
|
||||
are needed in case the converter
|
||||
+-----------+ in the registry needs to be
|
||||
| converter | cloned. That occurs when a
|
||||
+-----------+ unwrap target type is not
|
||||
^ contained within the Python object.
|
||||
|
|
||||
+------------------+-----+
|
||||
| |
|
||||
+--------+-------+ Exposes |
|
||||
| unwrapper_base | convertible() |
|
||||
+----------------+ |
|
||||
^ |
|
||||
| |
|
||||
+--------+----+ +-----+-----+
|
||||
| unwrapper<T>| | wrapper<T>|
|
||||
+-------------+ +-----------+
|
||||
Exposes T convert(PyObject*) Exposes PyObject* convert(T)
|
||||
|
||||
|
||||
unwrap:
|
||||
|
||||
constructed with a PyObject*, whose reference count is
|
||||
incremented.
|
||||
|
||||
find the registry entry for the target type
|
||||
|
||||
look in the collection of converters for one which claims to be
|
||||
able to convert the PyObject to the target type.
|
||||
|
||||
stick a pointer to the unwrapper in the unwrap object
|
||||
|
||||
when unwrap is queried for convertibility, it checks to see
|
||||
if it has a pointer to an unwrapper.
|
||||
|
||||
on conversion, the unwrapper is asked to allocate an
|
||||
implementation if the unwrap object isn't already holding
|
||||
one. The unwrap object "takes ownership" of the unwrapper's
|
||||
implementation. No memory allocation will actually take place
|
||||
unless this is a value conversion.
|
||||
|
||||
on destruction, the unwrapper is asked to free any implementation
|
||||
held by the unwrap object. No memory deallocation actually
|
||||
takes place unless this is a value conversion
|
||||
|
||||
on destruction, the reference count on the held PyObject is
|
||||
decremented.
|
||||
|
||||
We need to make sure that by default, you can't instantiate
|
||||
callback<> for reference and pointer return types: although the
|
||||
unwrappers may exist, they may convert by-value, which would cause
|
||||
the referent to be destroyed upon return.
|
||||
|
||||
wrap:
|
||||
|
||||
find the registry entry for the source type
|
||||
|
||||
see if there is a converter. If found, stick a pointer to it in
|
||||
the wrap object.
|
||||
|
||||
when queried for convertibility, it checks to see if it has a
|
||||
pointer to a converter.
|
||||
|
||||
on conversion, a reference to the target PyObject is held by the
|
||||
converter. Generally, the PyObject will have been created by the
|
||||
converter, but in certain cases it may be a pre-existing object,
|
||||
whose reference count will have been incremented.
|
||||
|
||||
when a wrap<T> x is used to return from a C++ function,
|
||||
x.release() is returned so that x no longer holds a reference to
|
||||
the PyObject when destroyed.
|
||||
|
||||
Otherwise, on destruction, any PyObject still held has its
|
||||
reference-count decremented.
|
||||
|
||||
|
||||
When a converter is created by the user, the appropriate element must
|
||||
be added to the registry; when it is destroyed, it must be removed
|
||||
from the registry.
|
||||
191
doc/news.html
191
doc/news.html
@@ -1,191 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="boost.css">
|
||||
|
||||
<title>Boost.Python - News/Change Log</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">News/Change Log</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt>11 Sept 2003</dt>
|
||||
|
||||
<dd>
|
||||
<ul>
|
||||
<li>Changed the response to multiple to-python converters being
|
||||
registered for the same type from a hard error into warning;
|
||||
Boost.Python now reports the offending type in the message.</li>
|
||||
|
||||
<li>Added builtin <code>std::wstring</code> conversions</li>
|
||||
|
||||
<li>Added <code>std::out_of_range</code> => Python
|
||||
<code>IndexError</code> exception conversion, thanks to <a href=
|
||||
"mailto:RaoulGough-at-yahoo.co.uk">Raoul Gough</a></li>
|
||||
</ul>
|
||||
</dd>
|
||||
|
||||
<dt>9 Sept 2003</dt>
|
||||
|
||||
<dd>Added new <code><a href="v2/str.html#str-spec">str</a></code></dd>
|
||||
|
||||
<dt>constructors which take a range of characters, allowing strings
|
||||
containing nul (<code>'\0'</code>) characters.</dt>
|
||||
|
||||
<dt>8 Sept 2003</dt>
|
||||
|
||||
<dd>Added the ability to create methods from function objects (with an
|
||||
<code>operator()</code>); see the <a href=
|
||||
"v2/make_function.html#make_function-spec">make_function</a> docs for
|
||||
more info.</dd>
|
||||
|
||||
<dt>10 August 2003</dt>
|
||||
|
||||
<dd>Added the new <code>properties</code> unit tests contributed by <a
|
||||
href="mailto:romany-at-actimize.com">Roman Yakovenko</a> and documented
|
||||
<code>add_static_property</code> at his urging.</dd>
|
||||
|
||||
<dt>1 August 2003</dt>
|
||||
|
||||
<dd>
|
||||
Added the new <code>arg</code> class contributed by <a href=
|
||||
"mailto:nickm-at-sitius.com">Nikolay Mladenov</a> which supplies the
|
||||
ability to wrap functions that can be called with ommitted arguments
|
||||
in the middle:
|
||||
<pre>
|
||||
void f(int x = 0, double y = 3.14, std::string z = std::string("foo"));
|
||||
|
||||
BOOST_PYTHON_MODULE(test)
|
||||
{
|
||||
def("f", f
|
||||
, (arg("x", 0), arg("y", 3.14), arg("z", "foo")));
|
||||
}
|
||||
|
||||
</pre>
|
||||
And in Python:
|
||||
<pre>
|
||||
>>> import test
|
||||
>>> f(0, z = "bar")
|
||||
>>> f(z = "bar", y = 0.0)
|
||||
</pre>
|
||||
Thanks, Nikolay!
|
||||
</dd>
|
||||
|
||||
<dt>22 July 2003</dt>
|
||||
|
||||
<dd>Killed the dreaded "bad argument type for builtin operation" error.
|
||||
Argument errors now show the actual and expected argument types!</dd>
|
||||
|
||||
<dt>19 July 2003</dt>
|
||||
|
||||
<dd>Added the new <code><a href=
|
||||
"v2/return_arg.html">return_arg</a></code> policy from <a href=
|
||||
"mailto:nickm-at-sitius.com">Nikolay Mladenov</a>. Thanks,
|
||||
Nikolay!</dd>
|
||||
|
||||
<dt>18 March, 2003</dt>
|
||||
|
||||
<dd><a href="mailto:Gottfried.Ganssauge-at-haufe.de">Gottfried
|
||||
Ganßauge</a> has contributed <a href=
|
||||
"v2/opaque_pointer_converter.html">opaque pointer support</a>.<br>
|
||||
<a href="nicodemus-at-globalite.com.br">Bruno da Silva de Oliveira</a>
|
||||
has contributed the exciting <a href="../pyste/index.html">Pyste</a>
|
||||
("Pie-steh") package.</dd>
|
||||
|
||||
<dt>24 February 2003</dt>
|
||||
|
||||
<dd>Finished improved support for <code>boost::shared_ptr</code>. Now
|
||||
any wrapped object of C++ class <code>X</code> can be converted
|
||||
automatically to <code>shared_ptr<X></code>, regardless of how it
|
||||
was wrapped. The <code>shared_ptr</code> will manage the lifetime of
|
||||
the Python object which supplied the <code>X</code>, rather than just
|
||||
the <code>X</code> object itself, and when such a
|
||||
<code>shared_ptr</code> is converted back to Python, the original
|
||||
Python object will be returned.</dd>
|
||||
|
||||
<dt>19 January 2003</dt>
|
||||
|
||||
<dd>Integrated <code>staticmethod</code> support from <a href=
|
||||
"mailto:nickm-at-sitius.com">Nikolay Mladenov</a>. Thanks,
|
||||
Nikolay!</dd>
|
||||
|
||||
<dt>29 December 2002</dt>
|
||||
|
||||
<dd>Added Visual Studio project file and instructions from Brett
|
||||
Calcott. Thanks, Brett!</dd>
|
||||
|
||||
<dt>20 December 2002</dt>
|
||||
|
||||
<dd>Added automatic downcasting for pointers, references, and smart
|
||||
pointers to polymorphic class types upon conversion to python</dd>
|
||||
|
||||
<dt>18 December 2002</dt>
|
||||
|
||||
<dd>Optimized from_python conversions for wrapped classes by putting
|
||||
the conversion logic in the shared library instead of registering
|
||||
separate converters for each class in each extension module</dd>
|
||||
|
||||
<dt>19 November 2002</dt>
|
||||
|
||||
<dd>Removed the need for users to cast base class member function
|
||||
pointers when used as arguments to <a href=
|
||||
"v2/class.html#class_-spec-modifiers">add_property</a></dd>
|
||||
|
||||
<dt>13 December 2002</dt>
|
||||
|
||||
<dd>Allow exporting of <a href=
|
||||
"v2/enum.html#enum_-spec"><code>enum_</code></a> values into enclosing
|
||||
<a href="v2/scope.html#scope-spec"><code>scope</code></a>.<br>
|
||||
Fixed unsigned integer conversions to deal correctly with numbers that
|
||||
are out-of-range of <code>signed long</code>.</dd>
|
||||
|
||||
<dt>14 November 2002</dt>
|
||||
|
||||
<dd>Auto-detection of class data members wrapped with <a href=
|
||||
"v2/data_members.html#make_getter-spec"><code>make_getter</code></a></dd>
|
||||
|
||||
<dt>13 November 2002</dt>
|
||||
|
||||
<dd>Full Support for <code>std::auto_ptr<></code> added.</dd>
|
||||
|
||||
<dt>October 2002</dt>
|
||||
|
||||
<dd>Ongoing updates and improvements to tutorial documentation</dd>
|
||||
|
||||
<dt>10 October 2002</dt>
|
||||
|
||||
<dd>Boost.Python V2 is released!</dd>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
11 September 2003
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href="../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002-2003. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,217 +0,0 @@
|
||||
How Runtime Polymorphism is expressed in Boost.Python:
|
||||
-----------------------------------------------------
|
||||
|
||||
struct A { virtual std::string f(); virtual ~A(); };
|
||||
|
||||
std::string call_f(A& x) { return x.f(); }
|
||||
|
||||
struct B { virtual std::string f() { return "B"; } };
|
||||
|
||||
struct Bcb : B
|
||||
{
|
||||
Bcb(PyObject* self) : m_self(self) {}
|
||||
|
||||
virtual std::string f() { return call_method<std::string>(m_sef, "f"); }
|
||||
static std::string f_default(B& b) { return b.B::f(); }
|
||||
|
||||
PyObject* m_self;
|
||||
};
|
||||
|
||||
struct C : B
|
||||
{
|
||||
virtual std::string f() { return "C"; }
|
||||
};
|
||||
|
||||
>>> class D(B):
|
||||
... def f():
|
||||
... return 'D'
|
||||
...
|
||||
>>> class E(B): pass
|
||||
...
|
||||
|
||||
|
||||
When we write, "invokes B::f non-virtually", we mean:
|
||||
|
||||
void g(B& x) { x.B::f(); }
|
||||
|
||||
This will call B::f() regardless of the dynamic type of x. Any other
|
||||
way of invoking B::f, including through a function pointer, is a
|
||||
"virtual invocation", and will call the most-derived override of f().
|
||||
|
||||
Case studies
|
||||
|
||||
C++\Python class
|
||||
\___A_____B_____C_____D____E___
|
||||
|
|
||||
A | 1
|
||||
|
|
||||
B | 2 3
|
||||
|
|
||||
Bcb | 4 5 6
|
||||
|
|
||||
C | 7 8
|
||||
|
|
||||
|
||||
|
||||
1. Simple case
|
||||
|
||||
2. Python A holds a B*. Probably won't happen once we have forced
|
||||
downcasting.
|
||||
|
||||
Requires:
|
||||
x.f() -> 'B'
|
||||
call_f(x) -> 'B'
|
||||
|
||||
Implies: A.f invokes A::f() (virtually or otherwise)
|
||||
|
||||
3. Python B holds a B*.
|
||||
|
||||
Requires:
|
||||
x.f() -> 'B'
|
||||
call_f(x) -> 'B'
|
||||
|
||||
Implies: B.f invokes B::f (virtually or otherwise)
|
||||
|
||||
|
||||
4. B constructed from Python
|
||||
|
||||
Requires:
|
||||
|
||||
x.f() -> 'B'
|
||||
call_f(x) -> 'B'
|
||||
|
||||
Implies: B.f invokes B::f non-virtually. Bcb::f invokes B::f
|
||||
non-virtually.
|
||||
|
||||
Question: Does it help if we arrange for Python B construction to
|
||||
build a true B object? Then this case doesn't arise.
|
||||
|
||||
|
||||
5. D is a Python class derived from B
|
||||
|
||||
Requires:
|
||||
|
||||
x.f() -> 'D'
|
||||
call_f(x) -> 'D'
|
||||
|
||||
Implies: Bcb::f must invoke call_method to look up the Python
|
||||
method override, otherwise call_f wouldn't work.
|
||||
|
||||
6. E is like D, but doesn't override f
|
||||
|
||||
Requires:
|
||||
|
||||
x.f() -> 'B'
|
||||
call_f(x) -> 'B'
|
||||
|
||||
Implies: B.f invokes B::f non-virtually. If it were virtual, x.f()
|
||||
would cause infinite recursion, because we've already
|
||||
determined that Bcb::f must invoke call_method to look up
|
||||
the Python method override.
|
||||
|
||||
7. Python B object holds a C*
|
||||
|
||||
Requires:
|
||||
|
||||
x.f() -> 'C'
|
||||
call_f(x) -> 'C'
|
||||
|
||||
Implies: B.f invokes B::f virtually.
|
||||
|
||||
8. C object constructed from Python
|
||||
|
||||
Requires:
|
||||
|
||||
x.f() -> 'C'
|
||||
call_f(x) -> 'C'
|
||||
|
||||
Implies: nothing new.
|
||||
|
||||
------
|
||||
|
||||
Total implications:
|
||||
|
||||
2: A.f invokes A::f() (virtually or otherwise)
|
||||
3: B.f invokes B::f (virtually or otherwise)
|
||||
4: B.f invokes B::f non-virtually. Bcb::f invokes B::f non-virtually
|
||||
6: B.f invokes B::f non-virtually.
|
||||
7: B.f invokes B::f virtually.
|
||||
|
||||
5: Bcb::f invokes call_method to look up the Python method
|
||||
|
||||
Though (4) is avoidable, clearly 6 and 7 are not, and they
|
||||
conflict. The implication is that B.f must choose its behavior
|
||||
according to the type of the contained C++ object. If it is Bcb, a
|
||||
non-virtual call to B::f must occur. Otherwise, a virtual call to B::f
|
||||
must occur. This is essentially the same scheme we had with
|
||||
Boost.Python v1.
|
||||
|
||||
Note: in early versions of Boost.Python v1, we solved this problem by
|
||||
introducing a new Python class in the hierarchy, so that D and E
|
||||
actually derive from a B', and B'.f invokes B::f non-virtually, while
|
||||
B.f invokes B::f virtually. However, people complained about the
|
||||
artificial class in the hierarchy, which was revealed when they tried
|
||||
to do normal kinds of Python introspection.
|
||||
|
||||
-------
|
||||
|
||||
Assumption: we will have a function which builds a virtual function
|
||||
dispatch callable Python object.
|
||||
|
||||
make_virtual_function(pvmf, default_impl, call_policies, dispatch_type)
|
||||
|
||||
Pseudocode:
|
||||
|
||||
Get first argument from Python arg tuple
|
||||
if it contains dispatch_type
|
||||
call default_impl
|
||||
else
|
||||
call through pvmf
|
||||
|
||||
|
||||
Open questions:
|
||||
|
||||
1. What about Python multiple inheritance? Do we have the right
|
||||
check in the if clause above?
|
||||
|
||||
A: Not quite. The correct test looks like:
|
||||
|
||||
Deduce target type of pvmf, i.e. T in R(T::*)(A1...AN).
|
||||
Find holder in first argument which holds T
|
||||
if it holds dispatch_type...
|
||||
|
||||
2. Can we make this more efficient?
|
||||
|
||||
The current "returning" mechanism will look up a holder for T
|
||||
again. I don't know if we know how to avoid that.
|
||||
|
||||
|
||||
OK, the solution involves reworking the call mechanism. This is
|
||||
neccesary anyway in order to enable wrapping of function objects.
|
||||
|
||||
It can result in a reduction in the overall amount of source code,
|
||||
because returning<> won't need to be specialized for every
|
||||
combination of function and member function... though it will still
|
||||
need a void specialization. We will still need a way to dispatch to
|
||||
member functions through a regular function interface. mem_fn is
|
||||
almost the right tool, but it only goes up to 8
|
||||
arguments. Forwarding is tricky if you don't want to incur copies.
|
||||
I think the trick is to use arg_from_python<T>::result_type for each
|
||||
argument to the forwarder.
|
||||
|
||||
Another option would be to use separate function, function object,
|
||||
and member function dispatchers. Once you know you have a member
|
||||
function, you don't need cv-qualified overloads to call it.
|
||||
|
||||
Hmm, while we're at this, maybe we should solve the write-back
|
||||
converter problem. Can we do it? Maybe not. Ralf doesn't want to
|
||||
write special write-back functions here, does he? He wants the
|
||||
converter to do the work automatically. We could add
|
||||
cleanup/destructor registration. That would relieve the client from
|
||||
having accessible destructors for types which are being converted by
|
||||
rvalue. I'm not sure that this will really save any code,
|
||||
however. It rather depends on the linker, doesn't it? I wonder if
|
||||
this can be done in a backwards-compatible fashion by generating the
|
||||
delete function when it's not supplied?
|
||||
|
||||
|
||||
@@ -1,344 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="boost.css">
|
||||
|
||||
<title>Boost.Python - Projects using Boost.Python</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Projects using Boost.Python</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Introduction</h2>
|
||||
|
||||
<p>This is a partial list of projects using Boost.Python. If you are
|
||||
using Boost.Python as your Python/C++ binding solution, we'd be proud to
|
||||
list your project on this page. Just <a href=
|
||||
"mailto:c++-sig@python.org">post</a> a short description of your project
|
||||
and how Boost.Python helps you get the job done, and we'll add it to this
|
||||
page .</p>
|
||||
<hr>
|
||||
|
||||
<h3>Data Analysis</h3>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><b><a href=
|
||||
"http://www.neuralynx.com/neuralab/index.htm">NeuraLab</a></b></dt>
|
||||
|
||||
<dd>Neuralab is a data analysis environment specifically tailored for
|
||||
neural data from <a href="http://www.neuralynx.com">Neuralynx</a>
|
||||
acquisition systems. Neuralab combines presentation quality graphics, a
|
||||
numerical analysis library, and the <a href=
|
||||
"http://www.python.org">Python</a> scripting engine in a single
|
||||
application. With Neuralab, Neuralynx users can perform common analysis
|
||||
tasks with just a few mouse clicks. More advanced users can create
|
||||
custom Python scripts, which can optionally be assigned to menus and
|
||||
mouse clicks.</dd>
|
||||
</dl>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><b>TSLib</b> - <a href="http://www.fortressinv.com">Fortress
|
||||
Investment Group LLC</a></dt>
|
||||
|
||||
<dd>
|
||||
Fortress Investment Group has contracted <a href=
|
||||
"http://www.boost-consulting.com">Boost Consulting</a> to develop
|
||||
core internal financial analysis tools in C++ and to prepare Python
|
||||
bindings for them using Boost.Python.
|
||||
|
||||
<p>Tom Barket of Fortress writes:</p>
|
||||
|
||||
<blockquote>
|
||||
We have a large C++ analytical library specialized for research in
|
||||
finance and economics, built for speed and mission critical
|
||||
stability. Yet Python offers us the flexibility to test out new
|
||||
ideas quickly and increase the productivity of our time versus
|
||||
working in C++. There are several key features which make Python
|
||||
stand out. Its elegance, stability, and breadth of resources on the
|
||||
web are all valuable, but the most important is its extensibility,
|
||||
due to its open source transparency. Boost.Python makes Python
|
||||
extensibility extremely simple and straightforward, yet preserves a
|
||||
great deal of power and control.
|
||||
</blockquote>
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h3>Educational</h3>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="http://edu.kde.org/kig"><b>Kig</b></a></dt>
|
||||
|
||||
<dd>
|
||||
<p>KDE Interactive Geometry is a high-school level educational tool,
|
||||
built for the KDE desktop. It is a nice tool to let students work
|
||||
with geometrical constructions. It is meant to be the most intuitive,
|
||||
yet featureful application of its kind.</p>
|
||||
|
||||
<p>Versions after 0.6.x (will) support objects built by the user
|
||||
himself in the Python language. The exporting of the relevant
|
||||
internal API's were done using Boost.Python, which made the process
|
||||
very easy.</p>
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h3>Enterprise Software</h3>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><b><a href="http://openwbem.sourceforge.net">OpenWBEM</a></b></dt>
|
||||
|
||||
<dd>
|
||||
The OpenWBEM project is an effort to develop an open-source
|
||||
implementation of Web Based Enterprise Management suitable for
|
||||
commercial and non-commercial application
|
||||
|
||||
<p><a href="mailto:dnuffer@sco.com">Dan Nuffer</a> writes:</p>
|
||||
|
||||
<blockquote>
|
||||
I'm using Boost.Python to wrap the client API of OpenWBEM.This will
|
||||
make it easier to do rapid prototyping, testing, and scripting when
|
||||
developing management solutions that use WBEM.
|
||||
</blockquote>
|
||||
</dd>
|
||||
|
||||
<dt><b><a href="http://www.transversal.com">Metafaq</a></b></dt>
|
||||
|
||||
<dd>
|
||||
Metafaq, from <a href="http://www.transversal.com">Transversal,
|
||||
Inc.</a>, is an enterprise level online knowledge base management
|
||||
system.
|
||||
|
||||
<p><a href="mailto:ben.young-at-transversal.com">Ben Young</a>
|
||||
writes:</p>
|
||||
|
||||
<blockquote>
|
||||
Boost.Python is used in an automated process to generate python
|
||||
bindings to our api which is exposed though multiple backends and
|
||||
frontends. This allows us to write quick tests and bespoke scripts
|
||||
to perform one off tasks without having to go through the full
|
||||
compilation cycle.
|
||||
</blockquote>
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h3>Graphics</h3>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><b><a href="http://sourceforge.net/projects/pyosg">OpenSceneGraph
|
||||
Bindings</a></b></dt>
|
||||
|
||||
<dd><a href="mailto:gideon@computer.org">Gideon May</a> has created a
|
||||
set of bindings for <a href=
|
||||
"http://www.openscenegraph.org">OpenSceneGraph</a>, a cross-platform
|
||||
C++/OpenGL library for the real-time visualization.<br>
|
||||
</dd>
|
||||
|
||||
<dt><a href=
|
||||
"http://www.procoders.net/pythonmagick"><b>PythonMagick</b></a></dt>
|
||||
|
||||
<dd>PythonMagick binds the <a href=
|
||||
"http://www.graphicsmagick.org">GraphicsMagick</a> image manipulation
|
||||
library to Python.<br>
|
||||
</dd>
|
||||
|
||||
<dt><b><a href=
|
||||
"http://www.slac.stanford.edu/grp/ek/hippodraw/index.html">HippoDraw</a></b></dt>
|
||||
|
||||
<dd>
|
||||
HippoDraw is a data analysis environment consisting of a canvas upon
|
||||
which graphs such as histograms, scattter plots, etc, are prsented.
|
||||
It has a highly interactive GUI interface, but some things you need
|
||||
to do with scripts. HippoDraw can be run as Python extension module
|
||||
so that all the manipulation can be done from either Python or the
|
||||
GUI.
|
||||
|
||||
<p>Before the web page came online, <a href=
|
||||
"mailto:Paul_Kunz@SLAC.Stanford.EDU">Paul F. Kunz</a> wrote:</p>
|
||||
|
||||
<blockquote>
|
||||
Don't have a web page for the project, but the organization's is <a
|
||||
href=
|
||||
"http://www.slac.stanford.edu">http://www.slac.stanford.edu</a>
|
||||
(the first web server site in America, I installed it).
|
||||
</blockquote>
|
||||
Which was just too cool a piece of trivia to omit.<br>
|
||||
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h3>Scientific Computing</h3>
|
||||
|
||||
<dl class="page index">
|
||||
<dt><a href="http://camfr.sourceforge.net"><b>CAMFR</b></a></dt>
|
||||
|
||||
<dd>
|
||||
CAMFR is a photonics and electromagnetics modelling tool. Python is
|
||||
used for computational steering.
|
||||
|
||||
<p><a href="mailto:Peter.Bienstman@rug.ac.be">Peter Bienstman</a>
|
||||
writes:</p>
|
||||
|
||||
<blockquote>
|
||||
Thanks for providing such a great tool!
|
||||
</blockquote>
|
||||
</dd>
|
||||
|
||||
<dt><a href="http://cctbx.sourceforge.net"><b>cctbx - Computational
|
||||
Crystallography Toolbox</b></a></dt>
|
||||
|
||||
<dd>
|
||||
Computational Crystallography is concerned with the derivation of
|
||||
atomic models of crystal structures, given experimental X-ray
|
||||
diffraction data. The cctbx is an open-source library of fundamental
|
||||
algorithms for crystallographic computations. The core algorithms are
|
||||
implemented in C++ and accessed through higher-level Python
|
||||
interfaces.
|
||||
|
||||
<p>The cctbx grew together with Boost.Python and is designed from the
|
||||
ground up as a hybrid Python/C++ system. With one minor exception,
|
||||
run-time polymorphism is completely handled by Python. C++
|
||||
compile-time polymorphism is used to implement performance critical
|
||||
algorithms. The Python and C++ layers are seamlessly integrated using
|
||||
Boost.Python.</p>
|
||||
|
||||
<p>The SourceForge cctbx project is organized in modules to
|
||||
facilitate use in non-crystallographic applications. The scitbx
|
||||
module implements a general purpose array family for scientific
|
||||
applications and pure C++ ports of FFTPACK and the LBFGS conjugate
|
||||
gradient minimizer.</p>
|
||||
</dd>
|
||||
|
||||
<dt><a href="http://www.llnl.gov/CASC/emsolve"><b>EMSolve</b></a></dt>
|
||||
|
||||
<dd>EMSolve is a provably stable, charge conserving, and energy
|
||||
conserving solver for Maxwell's equations.<br>
|
||||
</dd>
|
||||
|
||||
<dt><b><a href="http://cern.ch/gaudi">Gaudi</a></b> and <b><a href=
|
||||
"http://cern.ch/Gaudi/RootPython/">RootPython</a></b></dt>
|
||||
|
||||
<dd>
|
||||
Gaudi is a framework for particle physics collision data processing
|
||||
applications developed in the context of the LHCb and ATLAS
|
||||
experiments at CERN.
|
||||
|
||||
<p><a href="mailto:Pere.Mato@cern.ch">Pere Mato Vila</a> writes:</p>
|
||||
|
||||
<blockquote>
|
||||
We are using Boost.Python to provide scripting/interactive
|
||||
capability to our framework. We have a module called "GaudiPython"
|
||||
implemented using Boost.Python that allows the interaction with any
|
||||
framework service or algorithm from python. RootPython also uses
|
||||
Boost.Python to provide a generic "gateway" between the <a href=
|
||||
"http://root.cern.ch">ROOT</a> framework and python
|
||||
|
||||
<p>Boost.Python is great. We managed very quickly to interface our
|
||||
framework to python, which is great language. We are trying to
|
||||
facilitate to our physicists (end-users) a rapid analysis
|
||||
application development environment based on python. For that,
|
||||
Boost.Python plays and essential role.</p>
|
||||
</blockquote>
|
||||
</dd>
|
||||
|
||||
<dt><b><a href="http://www.esss.com.br">ESSS</a></b></dt>
|
||||
|
||||
<dd>
|
||||
ESSS (Engineering Simulation and Scientific Software) is a company
|
||||
that provides engineering solutions and acts in the brazilian and
|
||||
south-american market providing products and services related to
|
||||
Computational Fluid Dynamics and Image Analysis.
|
||||
|
||||
<p><a href="mailto:bruno@esss.com.br">Bruno da Silva de Oliveira</a>
|
||||
writes:</p>
|
||||
|
||||
<blockquote>
|
||||
Recently we moved our work from working exclusively with C++ to an
|
||||
hybrid-language approach, using Python and C++, with Boost.Python
|
||||
providing the layer between the two. The results are great so far!
|
||||
</blockquote>
|
||||
|
||||
<p>Two projects have been developed so far with this technology:</p>
|
||||
|
||||
<p><b><a href="http://www.esss.com.br/dev_simba.phtml">Simba</a></b>
|
||||
provides 3D visualization of geological formations gattered from the
|
||||
simulation of the evolution of oil systems, allowing the user to
|
||||
analyse various aspects of the simulation, like deformation, pressure
|
||||
and fluids, along the time of the simulation.</p>
|
||||
|
||||
<p><b><a href="http://www.esss.com.br/dev_aero.phtml">Aero</a></b>
|
||||
aims to construct a CFD with brazilian technology, which involves
|
||||
various companies and universities. ESSS is responsible for various
|
||||
of the application modules, including GUI and post-processing of
|
||||
results.</p>
|
||||
</dd>
|
||||
|
||||
<dt><b><a href="http://www.rationaldiscovery.com">Rational Discovery
|
||||
LLC</a></b></dt>
|
||||
|
||||
<dd>
|
||||
Rational Discovery provides computational modeling, combinatorial
|
||||
library design and custom software development services to the
|
||||
pharmaceutical, biotech and chemical industries. We do a substantial
|
||||
amount of internal research to develop new approaches for applying
|
||||
machine-learning techniques to solve chemical problems. Because we're
|
||||
a small organization and chemistry is a large and complex field, it
|
||||
is essential that we be able to quickly and easily prototype and test
|
||||
new algorithms.
|
||||
|
||||
<p>For our internal software, we implement core data structures in C
|
||||
and expose them to Python using Boost.Python. Algorithm development
|
||||
is done in Python and then translated to C if required (often it's
|
||||
not). This hybrid development approach not only greatly increases our
|
||||
productivity, but it also allows "non-developers" (people without C
|
||||
experience) to take part in method development. Learning C is a
|
||||
daunting task, but "Python fits your brain." (Thanks to Bruce Eckel
|
||||
for the quote.)</p>
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h3>Tools</h3>
|
||||
|
||||
<dl>
|
||||
<dt><a href="http://www.jayacard.org"><b>Jayacard</b></a></dt>
|
||||
|
||||
<dd>
|
||||
Jayacard aims at developing a secure portable open source operating
|
||||
system for contactless smart cards and a complete suite of high
|
||||
quality development tools to ease smart card OS and application
|
||||
development.
|
||||
|
||||
<p>The core of the smart card reader management is written in C++ but
|
||||
all the development tools are written in the friendly Python
|
||||
language. Boost plays the fundamental role of binding the tools to
|
||||
our core smart card reader library.</p>
|
||||
</dd>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
15 July, 2003</p>
|
||||
|
||||
<p><i>© Copyright <a href="../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002-2003. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,71 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="boost.css">
|
||||
|
||||
<title>Boost.Python - Support Resources</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Support Resources</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Synopsis</h2>
|
||||
|
||||
<p>This is a list of available resources for support with Boost.Python
|
||||
problems and feature requests. <b>Please try to resist emailing the
|
||||
Boost.Python developers directly for support.</b> Use the following
|
||||
resources instead; the developers are listening!</p>
|
||||
<hr>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><b><a href="http://www.boost-consulting.com">Boost
|
||||
Consulting</a></b> - Commercial support, development, training, and
|
||||
distribution for all the Boost libraries, from the people who brought
|
||||
you Boost.Python.<br>
|
||||
</dt>
|
||||
|
||||
<dt><b><a href=
|
||||
"http://www.boost.org/more/mailing_lists.htm#cplussig">The Python
|
||||
C++-sig</a></b> mailing list is a forum for discussing Python/C++
|
||||
interoperability, and Boost.Python in particular. Post your
|
||||
Boost.Python questions here.<br>
|
||||
</dt>
|
||||
|
||||
<dt>The <b>Boost.Python <a href=
|
||||
"http://www.python.org/cgi-bin/moinmoin/boost_2epython">Wiki
|
||||
Pages</a></b> established by Mike Rovner as part of the <a href=
|
||||
"http://www.python.org/cgi-bin/moinmoin">PythonInfo Wiki</a> serves as
|
||||
a forum to gather peoples' experience and as a cookbook.<br>
|
||||
</dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
12 Sept, 2003 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href="../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2003.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,112 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Auto-Overloading</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="default_arguments.html">
|
||||
<link rel="next" href="object_interface.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Auto-Overloading</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="default_arguments.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="object_interface.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
It was mentioned in passing in the previous section that
|
||||
<tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt> and <tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt>
|
||||
can also be used for overloaded functions and member functions with a
|
||||
common sequence of initial arguments. Here is an example:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>void </span><span class=identifier>foo</span><span class=special>()
|
||||
{
|
||||
/*...*/
|
||||
}
|
||||
|
||||
</span><span class=keyword>void </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>bool </span><span class=identifier>a</span><span class=special>)
|
||||
{
|
||||
/*...*/
|
||||
}
|
||||
|
||||
</span><span class=keyword>void </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>bool </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>b</span><span class=special>)
|
||||
{
|
||||
/*...*/
|
||||
}
|
||||
|
||||
</span><span class=keyword>void </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>bool </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>b</span><span class=special>, </span><span class=keyword>char </span><span class=identifier>c</span><span class=special>)
|
||||
{
|
||||
/*...*/
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Like in the previous section, we can generate thin wrappers for these
|
||||
overloaded functions in one-shot:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>BOOST_PYTHON_FUNCTION_OVERLOADS</span><span class=special>(</span><span class=identifier>foo_overloads</span><span class=special>, </span><span class=identifier>foo</span><span class=special>, </span><span class=number>0</span><span class=special>, </span><span class=number>3</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Then...</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"foo"</span><span class=special>, </span><span class=identifier>foo</span><span class=special>, </span><span class=identifier>foo_overloads</span><span class=special>());
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Notice though that we have a situation now where we have a minimum of zero
|
||||
(0) arguments and a maximum of 3 arguments.</p>
|
||||
<a name="manual_wrapping"></a><h2>Manual Wrapping</h2><p>
|
||||
It is important to emphasize however that <b>the overloaded functions must
|
||||
have a common sequence of initial arguments</b>. Otherwise, our scheme above
|
||||
will not work. If this is not the case, we have to wrap our functions
|
||||
<a href="overloading.html">
|
||||
manually</a>.</p>
|
||||
<p>
|
||||
Actually, we can mix and match manual wrapping of overloaded functions and
|
||||
automatic wrapping through <tt>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</tt> and
|
||||
its sister, <tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt>. Following up on our example
|
||||
presented in the section <a href="overloading.html">
|
||||
on overloading</a>, since the
|
||||
first 4 overload functins have a common sequence of initial arguments, we
|
||||
can use <tt>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</tt> to automatically wrap the
|
||||
first three of the <tt>def</tt>s and manually wrap just the last. Here's
|
||||
how we'll do this:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</span><span class=special>(</span><span class=identifier>xf_overloads</span><span class=special>, </span><span class=identifier>f</span><span class=special>, </span><span class=number>1</span><span class=special>, </span><span class=number>4</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Create a member function pointers as above for both X::f overloads:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>bool </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx1</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>double</span><span class=special>, </span><span class=keyword>char</span><span class=special>) = &</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
|
||||
</span><span class=keyword>int </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx2</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>int</span><span class=special>, </span><span class=keyword>int</span><span class=special>) = &</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Then...</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>fx1</span><span class=special>, </span><span class=identifier>xf_overloads</span><span class=special>());
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>fx2</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="default_arguments.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="object_interface.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,77 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Basic Interface</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="object_interface.html">
|
||||
<link rel="next" href="derived_object_types.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Basic Interface</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="object_interface.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="derived_object_types.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Class <tt>object</tt> wraps <tt>PyObject*</tt>. All the intricacies of dealing with
|
||||
<tt>PyObject</tt>s such as managing reference counting are handled by the
|
||||
<tt>object</tt> class. C++ object interoperability is seamless. Boost.Python C++
|
||||
<tt>object</tt>s can in fact be explicitly constructed from any C++ object.</p>
|
||||
<p>
|
||||
To illustrate, this Python code snippet:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>def </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>x</span><span class=special>, </span><span class=identifier>y</span><span class=special>):
|
||||
</span><span class=keyword>if </span><span class=special>(</span><span class=identifier>y </span><span class=special>== </span><span class=literal>'foo'</span><span class=special>):
|
||||
</span><span class=identifier>x</span><span class=special>[</span><span class=number>3</span><span class=special>:</span><span class=number>7</span><span class=special>] = </span><span class=literal>'bar'
|
||||
</span><span class=keyword>else</span><span class=special>:
|
||||
</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>items </span><span class=special>+= </span><span class=identifier>y</span><span class=special>(</span><span class=number>3</span><span class=special>, </span><span class=identifier>x</span><span class=special>)
|
||||
</span><span class=keyword>return </span><span class=identifier>x
|
||||
|
||||
</span><span class=identifier>def </span><span class=identifier>getfunc</span><span class=special>():
|
||||
</span><span class=keyword>return </span><span class=identifier>f</span><span class=special>;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Can be rewritten in C++ using Boost.Python facilities this way:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>object </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>object </span><span class=identifier>x</span><span class=special>, </span><span class=identifier>object </span><span class=identifier>y</span><span class=special>) {
|
||||
</span><span class=keyword>if </span><span class=special>(</span><span class=identifier>y </span><span class=special>== </span><span class=string>"foo"</span><span class=special>)
|
||||
</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>slice</span><span class=special>(</span><span class=number>3</span><span class=special>,</span><span class=number>7</span><span class=special>) = </span><span class=string>"bar"</span><span class=special>;
|
||||
</span><span class=keyword>else
|
||||
</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"items"</span><span class=special>) += </span><span class=identifier>y</span><span class=special>(</span><span class=number>3</span><span class=special>, </span><span class=identifier>x</span><span class=special>);
|
||||
</span><span class=keyword>return </span><span class=identifier>x</span><span class=special>;
|
||||
}
|
||||
</span><span class=identifier>object </span><span class=identifier>getfunc</span><span class=special>() {
|
||||
</span><span class=keyword>return </span><span class=identifier>object</span><span class=special>(</span><span class=identifier>f</span><span class=special>);
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Apart from cosmetic differences due to the fact that we are writing the
|
||||
code in C++, the look and feel should be immediately apparent to the Python
|
||||
coder.</p>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="object_interface.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="derived_object_types.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,194 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Building Hello World</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="quickstart.html">
|
||||
<link rel="next" href="exposing_classes.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Building Hello World</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="quickstart.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="exposing_classes.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<a name="from_start_to_finish"></a><h2>From Start To Finish</h2><p>
|
||||
Now the first thing you'd want to do is to build the Hello World module and
|
||||
try it for yourself in Python. In this section, we shall outline the steps
|
||||
necessary to achieve that. We shall use the build tool that comes bundled
|
||||
with every boost distribution: <b>bjam</b>.</p>
|
||||
<table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<p><img src="theme/lens.gif"></img> <b>Building without bjam</b><br>
|
||||
<br>
|
||||
Besides bjam, there are of course other ways to get your module built.
|
||||
What's written here should not be taken as "the one and only way".
|
||||
There are of course other build tools apart from <tt>bjam</tt>. </p>
|
||||
<p>Take note however that the preferred build tool for Boost.Python is <tt>bjam</tt>.
|
||||
There are so many ways to set up the build incorrectly. Experience shows
|
||||
that 90% of the "I can't build Boost.Python" problems come from
|
||||
people who had to use a different tool<tt></tt>.</p></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
We shall skip over the details. Our objective will be to simply create the
|
||||
hello world module and run it in Python. For a complete reference to
|
||||
building Boost.Python, check out: <a href="../../building.html">
|
||||
building.html</a>.
|
||||
After this brief <i>bjam</i> tutorial, we should have built two DLLs:</p>
|
||||
<ul><li>boost_python.dll</li><li>hello.pyd</li></ul><p>
|
||||
if you are on Windows, and</p>
|
||||
<ul><li>libboost_python.so</li><li>hello.so</li></ul><p>
|
||||
if you are on Unix.</p>
|
||||
<p>
|
||||
The tutorial example can be found in the directory:
|
||||
<tt>libs/python/example/tutorial</tt>. There, you can find:</p>
|
||||
<ul><li>hello.cpp</li><li>Jamfile</li></ul><p>
|
||||
The <tt>hello.cpp</tt> file is our C++ hello world example. The <tt>Jamfile</tt> is a
|
||||
minimalist <i>bjam</i> script that builds the DLLs for us.</p>
|
||||
<p>
|
||||
Before anything else, you should have the bjam executable in your boost
|
||||
directory or somewhere in your path such that <tt>bjam</tt> can be executed in
|
||||
the command line. Pre-built Boost.Jam executables are available for most
|
||||
platforms. For example, a pre-built Microsoft Windows bjam executable can
|
||||
be downloaded <a href="http://boost.sourceforge.net/jam-executables/bin.ntx86/bjam.zip">
|
||||
here</a>.
|
||||
The complete list of bjam pre-built
|
||||
executables can be found <a href="../../../../../tools/build/index.html#Jam">
|
||||
here</a>.</p>
|
||||
<a name="lets_jam_"></a><h2>Lets Jam!</h2><p>
|
||||
<img src="theme/jam.png"></img></p>
|
||||
<p>
|
||||
Here is our minimalist Jamfile:</p>
|
||||
<code><pre>
|
||||
subproject libs/python/example/tutorial ;
|
||||
|
||||
SEARCH on python.jam = $(BOOST_BUILD_PATH) ;
|
||||
include python.jam ;
|
||||
|
||||
extension hello # Declare a Python extension called hello
|
||||
: hello.cpp # source
|
||||
<dll>../../build/boost_python # dependencies
|
||||
;
|
||||
</pre></code><p>
|
||||
First, we need to specify our location in the boost project hierarchy.
|
||||
It so happens that the tutorial example is located in <tt>/libs/python/example/tutorial</tt>.
|
||||
Thus:</p>
|
||||
<code><pre>
|
||||
subproject libs/python/example/tutorial ;
|
||||
</pre></code><p>
|
||||
Then we will include the definitions needed by Python modules:</p>
|
||||
<code><pre>
|
||||
SEARCH on python.jam = $(BOOST_BUILD_PATH) ;
|
||||
include python.jam ;
|
||||
</pre></code><p>
|
||||
Finally we declare our <tt>hello</tt> extension:</p>
|
||||
<code><pre>
|
||||
extension hello # Declare a Python extension called hello
|
||||
: hello.cpp # source
|
||||
<dll>../../build/boost_python # dependencies
|
||||
;
|
||||
</pre></code><a name="running_bjam"></a><h2>Running bjam</h2><p>
|
||||
<i>bjam</i> is run using your operating system's command line interpreter.</p>
|
||||
<blockquote><p>Start it up.</p></blockquote><p>
|
||||
Make sure that the environment is set so that we can invoke the C++
|
||||
compiler. With MSVC, that would mean running the <tt>Vcvars32.bat</tt> batch
|
||||
file. For instance:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>C</span><span class=special>:\</span><span class=identifier>Program </span><span class=identifier>Files</span><span class=special>\</span><span class=identifier>Microsoft </span><span class=identifier>Visual </span><span class=identifier>Studio</span><span class=special>\</span><span class=identifier>VC98</span><span class=special>\</span><span class=identifier>bin</span><span class=special>\</span><span class=identifier>Vcvars32</span><span class=special>.</span><span class=identifier>bat
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Some environment variables will have to be setup for proper building of our
|
||||
Python modules. Example:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>set </span><span class=identifier>PYTHON_ROOT</span><span class=special>=</span><span class=identifier>c</span><span class=special>:/</span><span class=identifier>dev</span><span class=special>/</span><span class=identifier>tools</span><span class=special>/</span><span class=identifier>python
|
||||
</span><span class=identifier>set </span><span class=identifier>PYTHON_VERSION</span><span class=special>=</span><span class=number>2.2
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The above assumes that the Python installation is in <tt>c:/dev/tools/python</tt>
|
||||
and that we are using Python version 2.2. You'll have to tweak this path
|
||||
appropriately. <img src="theme/note.gif"></img> Be sure not to include a third number, e.g. <b>not</b> "2.2.1",
|
||||
even if that's the version you have.</p>
|
||||
<p>
|
||||
Now we are ready... Be sure to <tt>cd</tt> to <tt>libs/python/example/tutorial</tt>
|
||||
where the tutorial <tt>"hello.cpp"</tt> and the <tt>"Jamfile"</tt> is situated.</p>
|
||||
<p>
|
||||
Finally:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>bjam </span><span class=special>-</span><span class=identifier>sTOOLS</span><span class=special>=</span><span class=identifier>msvc
|
||||
</span></pre></code>
|
||||
<p>
|
||||
We are again assuming that we are using Microsoft Visual C++ version 6. If
|
||||
not, then you will have to specify the appropriate tool. See
|
||||
<a href="../../../../../tools/build/index.html">
|
||||
Building Boost Libraries</a> for
|
||||
further details.</p>
|
||||
<p>
|
||||
It should be building now:</p>
|
||||
<code><pre>
|
||||
cd C:\dev\boost\libs\python\example\tutorial
|
||||
bjam -sTOOLS=msvc
|
||||
...patience...
|
||||
...found 1703 targets...
|
||||
...updating 40 targets...
|
||||
</pre></code><p>
|
||||
And so on... Finally:</p>
|
||||
<code><pre>
|
||||
vc-C++ ..\..\..\..\libs\python\example\tutorial\bin\hello.pyd\msvc\debug\
|
||||
runtime-link-dynamic\hello.obj
|
||||
hello.cpp
|
||||
vc-Link ..\..\..\..\libs\python\example\tutorial\bin\hello.pyd\msvc\debug\
|
||||
runtime-link-dynamic\hello.pyd ..\..\..\..\libs\python\example\tutorial\bin\
|
||||
hello.pyd\msvc\debug\runtime-link-dynamic\hello.lib
|
||||
Creating library ..\..\..\..\libs\python\example\tutorial\bin\hello.pyd\
|
||||
msvc\debug\runtime-link-dynamic\hello.lib and object ..\..\..\..\libs\python\
|
||||
example\tutorial\bin\hello.pyd\msvc\debug\runtime-link-dynamic\hello.exp
|
||||
...updated 40 targets...
|
||||
</pre></code><p>
|
||||
If all is well, you should now have:</p>
|
||||
<ul><li>boost_python.dll</li><li>hello.pyd</li></ul><p>
|
||||
if you are on Windows, and</p>
|
||||
<ul><li>libboost_python.so</li><li>hello.so</li></ul><p>
|
||||
if you are on Unix.</p>
|
||||
<p>
|
||||
<tt>boost_python.dll</tt> can be found somewhere in <tt>libs\python\build\bin</tt>
|
||||
while <tt>hello.pyd</tt> can be found somewhere in
|
||||
<tt>libs\python\example\tutorial\bin</tt>. After a successful build, you can just
|
||||
link in these DLLs with the Python interpreter. In Windows for example, you
|
||||
can simply put these libraries inside the directory where the Python
|
||||
executable is.</p>
|
||||
<p>
|
||||
You may now fire up Python and run our hello module:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>import </span><span class=identifier>hello
|
||||
</span><span class=special>>>> </span><span class=identifier>print </span><span class=identifier>hello</span><span class=special>.</span><span class=identifier>greet</span><span class=special>()
|
||||
</span><span class=identifier>hello</span><span class=special>, </span><span class=identifier>world
|
||||
</span></pre></code>
|
||||
<blockquote><p><b>There you go... Have fun!</b></p></blockquote><table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="quickstart.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="exposing_classes.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,169 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Call Policies</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="functions.html">
|
||||
<link rel="next" href="overloading.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Call Policies</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="functions.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="overloading.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
In C++, we often deal with arguments and return types such as pointers
|
||||
and references. Such primitive types are rather, ummmm, low level and
|
||||
they really don't tell us much. At the very least, we don't know the
|
||||
owner of the pointer or the referenced object. No wonder languages
|
||||
such as Java and Python never deal with such low level entities. In
|
||||
C++, it's usually considered a good practice to use smart pointers
|
||||
which exactly describe ownership semantics. Still, even good C++
|
||||
interfaces use raw references and pointers sometimes, so Boost.Python
|
||||
must deal with them. To do this, it may need your help. Consider the
|
||||
following C++ function:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>X</span><span class=special>& </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>Y</span><span class=special>& </span><span class=identifier>y</span><span class=special>, </span><span class=identifier>Z</span><span class=special>* </span><span class=identifier>z</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
How should the library wrap this function? A naive approach builds a
|
||||
Python X object around result reference. This strategy might or might
|
||||
not work out. Here's an example where it didn't</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>x </span><span class=special>= </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>y</span><span class=special>, </span><span class=identifier>z</span><span class=special>) </span>##<span class=identifier>x </span><span class=identifier>refers </span><span class=identifier>to </span><span class=identifier>some </span><span class=identifier>C</span><span class=special>++ </span><span class=identifier>X
|
||||
</span><span class=special>>>> </span><span class=identifier>del </span><span class=identifier>y
|
||||
</span><span class=special>>>> </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>some_method</span><span class=special>() </span>##<span class=identifier>CRASH</span><span class=special>!
|
||||
</span></pre></code>
|
||||
<p>
|
||||
What's the problem?</p>
|
||||
<p>
|
||||
Well, what if f() was implemented as shown below:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>X</span><span class=special>& </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>Y</span><span class=special>& </span><span class=identifier>y</span><span class=special>, </span><span class=identifier>Z</span><span class=special>* </span><span class=identifier>z</span><span class=special>)
|
||||
{
|
||||
</span><span class=identifier>y</span><span class=special>.</span><span class=identifier>z </span><span class=special>= </span><span class=identifier>z</span><span class=special>;
|
||||
</span><span class=keyword>return </span><span class=identifier>y</span><span class=special>.</span><span class=identifier>x</span><span class=special>;
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The problem is that the lifetime of result X& is tied to the lifetime
|
||||
of y, because the f() returns a reference to a member of the y
|
||||
object. This idiom is is not uncommon and perfectly acceptable in the
|
||||
context of C++. However, Python users should not be able to crash the
|
||||
system just by using our C++ interface. In this case deleting y will
|
||||
invalidate the reference to X. We have a dangling reference.</p>
|
||||
<p>
|
||||
Here's what's happening:</p>
|
||||
<ol><li><tt>f</tt> is called passing in a reference to <tt>y</tt> and a pointer to <tt>z</tt></li><li>A reference to <tt>y.x</tt> is returned</li><li><tt>y</tt> is deleted. <tt>x</tt> is a dangling reference</li><li><tt>x.some_method()</tt> is called</li><li><b>BOOM!</b></li></ol><p>
|
||||
We could copy result into a new object:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>y</span><span class=special>, </span><span class=identifier>z</span><span class=special>).</span><span class=identifier>set</span><span class=special>(</span><span class=number>42</span><span class=special>) </span>##<span class=identifier>Result </span><span class=identifier>disappears
|
||||
</span><span class=special>>>> </span><span class=identifier>y</span><span class=special>.</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>get</span><span class=special>() </span>##<span class=identifier>No </span><span class=identifier>crash</span><span class=special>, </span><span class=identifier>but </span><span class=identifier>still </span><span class=identifier>bad
|
||||
</span><span class=number>3.14
|
||||
</span></pre></code>
|
||||
<p>
|
||||
This is not really our intent of our C++ interface. We've broken our
|
||||
promise that the Python interface should reflect the C++ interface as
|
||||
closely as possible.</p>
|
||||
<p>
|
||||
Our problems do not end there. Suppose Y is implemented as follows:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Y
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>X </span><span class=identifier>x</span><span class=special>; </span><span class=identifier>Z</span><span class=special>* </span><span class=identifier>z</span><span class=special>;
|
||||
</span><span class=keyword>int </span><span class=identifier>z_value</span><span class=special>() { </span><span class=keyword>return </span><span class=identifier>z</span><span class=special>-></span><span class=identifier>value</span><span class=special>(); }
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Notice that the data member <tt>z</tt> is held by class Y using a raw
|
||||
pointer. Now we have a potential dangling pointer problem inside Y:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>x </span><span class=special>= </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>y</span><span class=special>, </span><span class=identifier>z</span><span class=special>) </span>##<span class=identifier>y </span><span class=identifier>refers </span><span class=identifier>to </span><span class=identifier>z
|
||||
</span><span class=special>>>> </span><span class=identifier>del </span><span class=identifier>z </span>##<span class=identifier>Kill </span><span class=identifier>the </span><span class=identifier>z </span><span class=identifier>object
|
||||
</span><span class=special>>>> </span><span class=identifier>y</span><span class=special>.</span><span class=identifier>z_value</span><span class=special>() </span>##<span class=identifier>CRASH</span><span class=special>!
|
||||
</span></pre></code>
|
||||
<p>
|
||||
For reference, here's the implementation of <tt>f</tt> again:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>X</span><span class=special>& </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>Y</span><span class=special>& </span><span class=identifier>y</span><span class=special>, </span><span class=identifier>Z</span><span class=special>* </span><span class=identifier>z</span><span class=special>)
|
||||
{
|
||||
</span><span class=identifier>y</span><span class=special>.</span><span class=identifier>z </span><span class=special>= </span><span class=identifier>z</span><span class=special>;
|
||||
</span><span class=keyword>return </span><span class=identifier>y</span><span class=special>.</span><span class=identifier>x</span><span class=special>;
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Here's what's happening:</p>
|
||||
<ol><li><tt>f</tt> is called passing in a reference to <tt>y</tt> and a pointer to <tt>z</tt></li><li>A pointer to <tt>z</tt> is held by <tt>y</tt></li><li>A reference to <tt>y.x</tt> is returned</li><li><tt>z</tt> is deleted. <tt>y.z</tt> is a dangling pointer</li><li><tt>y.z_value()</tt> is called</li><li><tt>z->value()</tt> is called</li><li><b>BOOM!</b></li></ol><a name="call_policies"></a><h2>Call Policies</h2><p>
|
||||
Call Policies may be used in situations such as the example detailed above.
|
||||
In our example, <tt>return_internal_reference</tt> and <tt>with_custodian_and_ward</tt>
|
||||
are our friends:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>f</span><span class=special>,
|
||||
</span><span class=identifier>return_internal_reference</span><span class=special><</span><span class=number>1</span><span class=special>,
|
||||
</span><span class=identifier>with_custodian_and_ward</span><span class=special><</span><span class=number>1</span><span class=special>, </span><span class=number>2</span><span class=special>> >());
|
||||
</span></pre></code>
|
||||
<p>
|
||||
What are the <tt>1</tt> and <tt>2</tt> parameters, you ask?</p>
|
||||
<code><pre>
|
||||
<span class=identifier>return_internal_reference</span><span class=special><</span><span class=number>1
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Informs Boost.Python that the first argument, in our case <tt>Y& y</tt>, is the
|
||||
owner of the returned reference: <tt>X&</tt>. The "<tt>1</tt>" simply specifies the
|
||||
first argument. In short: "return an internal reference <tt>X&</tt> owned by the
|
||||
1st argument <tt>Y& y</tt>".</p>
|
||||
<code><pre>
|
||||
<span class=identifier>with_custodian_and_ward</span><span class=special><</span><span class=number>1</span><span class=special>, </span><span class=number>2</span><span class=special>>
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Informs Boost.Python that the lifetime of the argument indicated by ward
|
||||
(i.e. the 2nd argument: <tt>Z* z</tt>) is dependent on the lifetime of the
|
||||
argument indicated by custodian (i.e. the 1st argument: <tt>Y& y</tt>).</p>
|
||||
<p>
|
||||
It is also important to note that we have defined two policies above. Two
|
||||
or more policies can be composed by chaining. Here's the general syntax:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>policy1</span><span class=special><</span><span class=identifier>args</span><span class=special>...,
|
||||
</span><span class=identifier>policy2</span><span class=special><</span><span class=identifier>args</span><span class=special>...,
|
||||
</span><span class=identifier>policy3</span><span class=special><</span><span class=identifier>args</span><span class=special>...> > >
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Here is the list of predefined call policies. A complete reference detailing
|
||||
these can be found <a href="../../v2/reference.html#models_of_call_policies">
|
||||
here</a>.</p>
|
||||
<ul><li><b>with_custodian_and_ward</b><br> Ties lifetimes of the arguments</li><li><b>with_custodian_and_ward_postcall</b><br> Ties lifetimes of the arguments and results</li><li><b>return_internal_reference</b><br> Ties lifetime of one argument to that of result</li><li><b>return_value_policy<T> with T one of:</b><br></li><li><b>reference_existing_object</b><br>naïve (dangerous) approach</li><li><b>copy_const_reference</b><br>Boost.Python v1 approach</li><li><b>copy_non_const_reference</b><br></li><li><b>manage_new_object</b><br> Adopt a pointer and hold the instance</li></ul><table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<img src="theme/smiley.gif"></img> <b>Remember the Zen, Luke:</b><br><br>
|
||||
"Explicit is better than implicit"<br>
|
||||
"In the face of ambiguity, refuse the temptation to guess"<br> </td>
|
||||
</tr>
|
||||
</table>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="functions.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="overloading.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,78 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Class Data Members</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="constructors.html">
|
||||
<link rel="next" href="class_properties.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Class Data Members</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="constructors.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_properties.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Data members may also be exposed to Python so that they can be
|
||||
accessed as attributes of the corresponding Python class. Each data
|
||||
member that we wish to be exposed may be regarded as <b>read-only</b> or
|
||||
<b>read-write</b>. Consider this class <tt>Var</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Var
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>Var</span><span class=special>(</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>name</span><span class=special>) : </span><span class=identifier>name</span><span class=special>(</span><span class=identifier>name</span><span class=special>), </span><span class=identifier>value</span><span class=special>() {}
|
||||
</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=keyword>const </span><span class=identifier>name</span><span class=special>;
|
||||
</span><span class=keyword>float </span><span class=identifier>value</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Our C++ <tt>Var</tt> class and its data members can be exposed to Python:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Var</span><span class=special>>(</span><span class=string>"Var"</span><span class=special>, </span><span class=identifier>init</span><span class=special><</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>>())
|
||||
.</span><span class=identifier>def_readonly</span><span class=special>(</span><span class=string>"name"</span><span class=special>, &</span><span class=identifier>Var</span><span class=special>::</span><span class=identifier>name</span><span class=special>)
|
||||
.</span><span class=identifier>def_readwrite</span><span class=special>(</span><span class=string>"value"</span><span class=special>, &</span><span class=identifier>Var</span><span class=special>::</span><span class=identifier>value</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Then, in Python, assuming we have placed our Var class inside the namespace
|
||||
hello as we did before:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>x </span><span class=special>= </span><span class=identifier>hello</span><span class=special>.</span><span class=identifier>Var</span><span class=special>(</span><span class=literal>'pi'</span><span class=special>)
|
||||
>>> </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>value </span><span class=special>= </span><span class=number>3.14
|
||||
</span><span class=special>>>> </span><span class=identifier>print </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>name</span><span class=special>, </span><span class=literal>'is around'</span><span class=special>, </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>value
|
||||
</span><span class=identifier>pi </span><span class=identifier>is </span><span class=identifier>around </span><span class=number>3.14
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Note that <tt>name</tt> is exposed as <b>read-only</b> while <tt>value</tt> is exposed
|
||||
as <b>read-write</b>.</p>
|
||||
<code><pre>
|
||||
>>> x.name = 'e' # can't change name
|
||||
Traceback (most recent call last):
|
||||
File "<stdin>", line 1, in ?
|
||||
AttributeError: can't set attribute
|
||||
</pre></code><table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="constructors.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_properties.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,109 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Class Operators/Special Functions</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="virtual_functions_with_default_implementations.html">
|
||||
<link rel="next" href="functions.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Class Operators/Special Functions</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="virtual_functions_with_default_implementations.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="functions.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<a name="python_operators"></a><h2>Python Operators</h2><p>
|
||||
C is well known for the abundance of operators. C++ extends this to the
|
||||
extremes by allowing operator overloading. Boost.Python takes advantage of
|
||||
this and makes it easy to wrap C++ operator-powered classes.</p>
|
||||
<p>
|
||||
Consider a file position class <tt>FilePos</tt> and a set of operators that take
|
||||
on FilePos instances:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>class </span><span class=identifier>FilePos </span><span class=special>{ /*...*/ };
|
||||
|
||||
</span><span class=identifier>FilePos </span><span class=keyword>operator</span><span class=special>+(</span><span class=identifier>FilePos</span><span class=special>, </span><span class=keyword>int</span><span class=special>);
|
||||
</span><span class=identifier>FilePos </span><span class=keyword>operator</span><span class=special>+(</span><span class=keyword>int</span><span class=special>, </span><span class=identifier>FilePos</span><span class=special>);
|
||||
</span><span class=keyword>int </span><span class=keyword>operator</span><span class=special>-(</span><span class=identifier>FilePos</span><span class=special>, </span><span class=identifier>FilePos</span><span class=special>);
|
||||
</span><span class=identifier>FilePos </span><span class=keyword>operator</span><span class=special>-(</span><span class=identifier>FilePos</span><span class=special>, </span><span class=keyword>int</span><span class=special>);
|
||||
</span><span class=identifier>FilePos</span><span class=special>& </span><span class=keyword>operator</span><span class=special>+=(</span><span class=identifier>FilePos</span><span class=special>&, </span><span class=keyword>int</span><span class=special>);
|
||||
</span><span class=identifier>FilePos</span><span class=special>& </span><span class=keyword>operator</span><span class=special>-=(</span><span class=identifier>FilePos</span><span class=special>&, </span><span class=keyword>int</span><span class=special>);
|
||||
</span><span class=keyword>bool </span><span class=keyword>operator</span><span class=special><(</span><span class=identifier>FilePos</span><span class=special>, </span><span class=identifier>FilePos</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The class and the various operators can be mapped to Python rather easily
|
||||
and intuitively:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>FilePos</span><span class=special>>(</span><span class=string>"FilePos"</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>self </span><span class=special>+ </span><span class=keyword>int</span><span class=special>()) // </span><span class=identifier>__add__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=keyword>int</span><span class=special>() + </span><span class=identifier>self</span><span class=special>) // </span><span class=identifier>__radd__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>self </span><span class=special>- </span><span class=identifier>self</span><span class=special>) // </span><span class=identifier>__sub__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>self </span><span class=special>- </span><span class=keyword>int</span><span class=special>()) // </span><span class=identifier>__sub__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>self </span><span class=special>+= </span><span class=keyword>int</span><span class=special>()) // </span><span class=identifier>__iadd__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>self </span><span class=special>-= </span><span class=identifier>other</span><span class=special><</span><span class=keyword>int</span><span class=special>>())
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>self </span><span class=special>< </span><span class=identifier>self</span><span class=special>); // </span><span class=identifier>__lt__
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The code snippet above is very clear and needs almost no explanation at
|
||||
all. It is virtually the same as the operators' signatures. Just take
|
||||
note that <tt>self</tt> refers to FilePos object. Also, not every class <tt>T</tt> that
|
||||
you might need to interact with in an operator expression is (cheaply)
|
||||
default-constructible. You can use <tt>other<T>()</tt> in place of an actual
|
||||
<tt>T</tt> instance when writing "self expressions".</p>
|
||||
<a name="special_methods"></a><h2>Special Methods</h2><p>
|
||||
Python has a few more <i>Special Methods</i>. Boost.Python supports all of the
|
||||
standard special method names supported by real Python class instances. A
|
||||
similar set of intuitive interfaces can also be used to wrap C++ functions
|
||||
that correspond to these Python <i>special functions</i>. Example:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>class </span><span class=identifier>Rational
|
||||
</span><span class=special>{ </span><span class=keyword>operator </span><span class=keyword>double</span><span class=special>() </span><span class=keyword>const</span><span class=special>; };
|
||||
|
||||
</span><span class=identifier>Rational </span><span class=identifier>pow</span><span class=special>(</span><span class=identifier>Rational</span><span class=special>, </span><span class=identifier>Rational</span><span class=special>);
|
||||
</span><span class=identifier>Rational </span><span class=identifier>abs</span><span class=special>(</span><span class=identifier>Rational</span><span class=special>);
|
||||
</span><span class=identifier>ostream</span><span class=special>& </span><span class=keyword>operator</span><span class=special><<(</span><span class=identifier>ostream</span><span class=special>&,</span><span class=identifier>Rational</span><span class=special>);
|
||||
|
||||
</span><span class=identifier>class_</span><span class=special><</span><span class=identifier>Rational</span><span class=special>>()
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>float_</span><span class=special>(</span><span class=identifier>self</span><span class=special>)) // </span><span class=identifier>__float__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>pow</span><span class=special>(</span><span class=identifier>self</span><span class=special>, </span><span class=identifier>other</span><span class=special><</span><span class=identifier>Rational</span><span class=special>>)) // </span><span class=identifier>__pow__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>abs</span><span class=special>(</span><span class=identifier>self</span><span class=special>)) // </span><span class=identifier>__abs__
|
||||
</span><span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>str</span><span class=special>(</span><span class=identifier>self</span><span class=special>)) // </span><span class=identifier>__str__
|
||||
</span><span class=special>;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Need we say more?</p>
|
||||
<table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<img src="theme/lens.gif"></img> What is the business of <tt>operator<<</tt> <tt>.def(str(self))</tt>?
|
||||
Well, the method <tt>str</tt> requires the <tt>operator<<</tt> to do its work (i.e.
|
||||
<tt>operator<<</tt> is used by the method defined by def(str(self)). </td>
|
||||
</tr>
|
||||
</table>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="virtual_functions_with_default_implementations.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="functions.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,81 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Class Properties</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="class_data_members.html">
|
||||
<link rel="next" href="inheritance.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Class Properties</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_data_members.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="inheritance.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
In C++, classes with public data members are usually frowned
|
||||
upon. Well designed classes that take advantage of encapsulation hide
|
||||
the class' data members. The only way to access the class' data is
|
||||
through access (getter/setter) functions. Access functions expose class
|
||||
properties. Here's an example:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Num
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>Num</span><span class=special>();
|
||||
</span><span class=keyword>float </span><span class=identifier>get</span><span class=special>() </span><span class=keyword>const</span><span class=special>;
|
||||
</span><span class=keyword>void </span><span class=identifier>set</span><span class=special>(</span><span class=keyword>float </span><span class=identifier>value</span><span class=special>);
|
||||
...
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
However, in Python attribute access is fine; it doesn't neccessarily break
|
||||
encapsulation to let users handle attributes directly, because the
|
||||
attributes can just be a different syntax for a method call. Wrapping our
|
||||
<tt>Num</tt> class using Boost.Python:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Num</span><span class=special>>(</span><span class=string>"Num"</span><span class=special>)
|
||||
.</span><span class=identifier>add_property</span><span class=special>(</span><span class=string>"rovalue"</span><span class=special>, &</span><span class=identifier>Num</span><span class=special>::</span><span class=identifier>get</span><span class=special>)
|
||||
.</span><span class=identifier>add_property</span><span class=special>(</span><span class=string>"value"</span><span class=special>, &</span><span class=identifier>Num</span><span class=special>::</span><span class=identifier>get</span><span class=special>, &</span><span class=identifier>Num</span><span class=special>::</span><span class=identifier>set</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
And at last, in Python:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>x </span><span class=special>= </span><span class=identifier>Num</span><span class=special>()
|
||||
>>> </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>value </span><span class=special>= </span><span class=number>3.14
|
||||
</span><span class=special>>>> </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>value</span><span class=special>, </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>rovalue
|
||||
</span><span class=special>(</span><span class=number>3.14</span><span class=special>, </span><span class=number>3.14</span><span class=special>)
|
||||
>>> </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>rovalue </span><span class=special>= </span><span class=number>2.17 </span>##<span class=identifier>error</span><span class=special>!
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Take note that the class property <tt>rovalue</tt> is exposed as <b>read-only</b>
|
||||
since the <tt>rovalue</tt> setter member function is not passed in:</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>add_property</span><span class=special>(</span><span class=string>"rovalue"</span><span class=special>, &</span><span class=identifier>Num</span><span class=special>::</span><span class=identifier>get</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_data_members.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="inheritance.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,129 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Class Virtual Functions</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="inheritance.html">
|
||||
<link rel="next" href="deriving_a_python_class.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Class Virtual Functions</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="inheritance.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="deriving_a_python_class.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
In this section, we shall learn how to make functions behave
|
||||
polymorphically through virtual functions. Continuing our example, let us
|
||||
add a virtual function to our <tt>Base</tt> class:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Base
|
||||
</span><span class=special>{
|
||||
</span><span class=keyword>virtual </span><span class=keyword>int </span><span class=identifier>f</span><span class=special>() = </span><span class=number>0</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Since <tt>f</tt> is a pure virtual function, <tt>Base</tt> is now an abstract
|
||||
class. Given an instance of our class, the free function <tt>call_f</tt>
|
||||
calls some implementation of this virtual function in a concrete
|
||||
derived class:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>int </span><span class=identifier>call_f</span><span class=special>(</span><span class=identifier>Base</span><span class=special>& </span><span class=identifier>b</span><span class=special>) { </span><span class=keyword>return </span><span class=identifier>b</span><span class=special>.</span><span class=identifier>f</span><span class=special>(); }
|
||||
</span></pre></code>
|
||||
<p>
|
||||
To allow this function to be implemented in a Python derived class, we
|
||||
need to create a class wrapper:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>BaseWrap </span><span class=special>: </span><span class=identifier>Base
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>BaseWrap</span><span class=special>(</span><span class=identifier>PyObject</span><span class=special>* </span><span class=identifier>self_</span><span class=special>)
|
||||
: </span><span class=identifier>self</span><span class=special>(</span><span class=identifier>self_</span><span class=special>) {}
|
||||
</span><span class=keyword>int </span><span class=identifier>f</span><span class=special>() { </span><span class=keyword>return </span><span class=identifier>call_method</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=identifier>self</span><span class=special>, </span><span class=string>"f"</span><span class=special>); }
|
||||
</span><span class=identifier>PyObject</span><span class=special>* </span><span class=identifier>self</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<img src="theme/lens.gif"></img> <b>member function and methods</b><br><br> Python, like
|
||||
many object oriented languages uses the term <b>methods</b>. Methods
|
||||
correspond roughly to C++'s <b>member functions</b> </td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Our class wrapper <tt>BaseWrap</tt> is derived from <tt>Base</tt>. Its overridden
|
||||
virtual member function <tt>f</tt> in effect calls the corresponding method
|
||||
of the Python object <tt>self</tt>, which is a pointer back to the Python
|
||||
<tt>Base</tt> object holding our <tt>BaseWrap</tt> instance.</p>
|
||||
<table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<img src="theme/note.gif"></img> <b>Why do we need BaseWrap?</b><br><br>
|
||||
|
||||
<i>You may ask</i>, "Why do we need the <tt>BaseWrap</tt> derived class? This could
|
||||
have been designed so that everything gets done right inside of
|
||||
Base."<br><br>
|
||||
|
||||
One of the goals of Boost.Python is to be minimally intrusive on an
|
||||
existing C++ design. In principle, it should be possible to expose the
|
||||
interface for a 3rd party library without changing it. To unintrusively
|
||||
hook into the virtual functions so that a Python override may be called, we
|
||||
must use a derived class.<br><br>
|
||||
|
||||
Note however that you don't need to do this to get methods overridden
|
||||
in Python to behave virtually when called <i>from</i> <b>Python</b>. The only
|
||||
time you need to do the <tt>BaseWrap</tt> dance is when you have a virtual
|
||||
function that's going to be overridden in Python and called
|
||||
polymorphically <i>from</i> <b>C++</b>. </td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Wrapping <tt>Base</tt> and the free function <tt>call_f</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Base</span><span class=special>, </span><span class=identifier>BaseWrap</span><span class=special>, </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>noncopyable</span><span class=special>>(</span><span class=string>"Base"</span><span class=special>, </span><span class=identifier>no_init</span><span class=special>)
|
||||
;
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"call_f"</span><span class=special>, </span><span class=identifier>call_f</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Notice that we parameterized the <tt>class_</tt> template with <tt>BaseWrap</tt> as the
|
||||
second parameter. What is <tt>noncopyable</tt>? Without it, the library will try
|
||||
to create code for converting Base return values of wrapped functions to
|
||||
Python. To do that, it needs Base's copy constructor... which isn't
|
||||
available, since Base is an abstract class.</p>
|
||||
<p>
|
||||
In Python, let us try to instantiate our <tt>Base</tt> class:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>base </span><span class=special>= </span><span class=identifier>Base</span><span class=special>()
|
||||
</span><span class=identifier>RuntimeError</span><span class=special>: </span><span class=identifier>This </span><span class=keyword>class </span><span class=identifier>cannot </span><span class=identifier>be </span><span class=identifier>instantiated </span><span class=identifier>from </span><span class=identifier>Python
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Why is it an error? <tt>Base</tt> is an abstract class. As such it is advisable
|
||||
to define the Python wrapper with <tt>no_init</tt> as we have done above. Doing
|
||||
so will disallow abstract base classes such as <tt>Base</tt> to be instantiated.</p>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="inheritance.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="deriving_a_python_class.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,102 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Constructors</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="exposing_classes.html">
|
||||
<link rel="next" href="class_data_members.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Constructors</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="exposing_classes.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_data_members.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Our previous example didn't have any explicit constructors.
|
||||
Since <tt>World</tt> is declared as a plain struct, it has an implicit default
|
||||
constructor. Boost.Python exposes the default constructor by default,
|
||||
which is why we were able to write</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>planet </span><span class=special>= </span><span class=identifier>hello</span><span class=special>.</span><span class=identifier>World</span><span class=special>()
|
||||
</span></pre></code>
|
||||
<p>
|
||||
We may wish to wrap a class with a non-default constructor. Let us
|
||||
build on our previous example:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>World
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>World</span><span class=special>(</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>): </span><span class=identifier>msg</span><span class=special>(</span><span class=identifier>msg</span><span class=special>) {} // </span><span class=identifier>added </span><span class=identifier>constructor
|
||||
</span><span class=keyword>void </span><span class=identifier>set</span><span class=special>(</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>) { </span><span class=keyword>this</span><span class=special>-></span><span class=identifier>msg </span><span class=special>= </span><span class=identifier>msg</span><span class=special>; }
|
||||
</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>greet</span><span class=special>() { </span><span class=keyword>return </span><span class=identifier>msg</span><span class=special>; }
|
||||
</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
This time <tt>World</tt> has no default constructor; our previous
|
||||
wrapping code would fail to compile when the library tried to expose
|
||||
it. We have to tell <tt>class_<World></tt> about the constructor we want to
|
||||
expose instead.</p>
|
||||
<code><pre>
|
||||
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>python</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
|
||||
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>python</span><span class=special>;
|
||||
|
||||
</span><span class=identifier>BOOST_PYTHON_MODULE</span><span class=special>(</span><span class=identifier>hello</span><span class=special>)
|
||||
{
|
||||
</span><span class=identifier>class_</span><span class=special><</span><span class=identifier>World</span><span class=special>>(</span><span class=string>"World"</span><span class=special>, </span><span class=identifier>init</span><span class=special><</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>>())
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"greet"</span><span class=special>, &</span><span class=identifier>World</span><span class=special>::</span><span class=identifier>greet</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"set"</span><span class=special>, &</span><span class=identifier>World</span><span class=special>::</span><span class=identifier>set</span><span class=special>)
|
||||
;
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
<tt>init<std::string>()</tt> exposes the constructor taking in a
|
||||
<tt>std::string</tt> (in Python, constructors are spelled
|
||||
"<tt>"__init__"</tt>").</p>
|
||||
<p>
|
||||
We can expose additional constructors by passing more <tt>init<...></tt>s to
|
||||
the <tt>def()</tt> member function. Say for example we have another World
|
||||
constructor taking in two doubles:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>World</span><span class=special>>(</span><span class=string>"World"</span><span class=special>, </span><span class=identifier>init</span><span class=special><</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>>())
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>init</span><span class=special><</span><span class=keyword>double</span><span class=special>, </span><span class=keyword>double</span><span class=special>>())
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"greet"</span><span class=special>, &</span><span class=identifier>World</span><span class=special>::</span><span class=identifier>greet</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"set"</span><span class=special>, &</span><span class=identifier>World</span><span class=special>::</span><span class=identifier>set</span><span class=special>)
|
||||
;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
On the other hand, if we do not wish to expose any constructors at
|
||||
all, we may use <tt>no_init</tt> instead:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Abstract</span><span class=special>>(</span><span class=string>"Abstract"</span><span class=special>, </span><span class=identifier>no_init</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
This actually adds an <tt>__init__</tt> method which always raises a
|
||||
Python RuntimeError exception.</p>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="exposing_classes.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_data_members.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,158 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Default Arguments</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="overloading.html">
|
||||
<link rel="next" href="auto_overloading.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Default Arguments</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="overloading.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="auto_overloading.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Boost.Python wraps (member) function pointers. Unfortunately, C++ function
|
||||
pointers carry no default argument info. Take a function <tt>f</tt> with default
|
||||
arguments:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>int </span><span class=identifier>f</span><span class=special>(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>double </span><span class=special>= </span><span class=number>3.14</span><span class=special>, </span><span class=keyword>char </span><span class=keyword>const</span><span class=special>* = </span><span class=string>"hello"</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
But the type of a pointer to the function <tt>f</tt> has no information
|
||||
about its default arguments:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>int</span><span class=special>(*</span><span class=identifier>g</span><span class=special>)(</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>double</span><span class=special>,</span><span class=keyword>char </span><span class=keyword>const</span><span class=special>*) = </span><span class=identifier>f</span><span class=special>; // </span><span class=identifier>defaults </span><span class=identifier>lost</span><span class=special>!
|
||||
</span></pre></code>
|
||||
<p>
|
||||
When we pass this function pointer to the <tt>def</tt> function, there is no way
|
||||
to retrieve the default arguments:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>f</span><span class=special>); // </span><span class=identifier>defaults </span><span class=identifier>lost</span><span class=special>!
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Because of this, when wrapping C++ code, we had to resort to manual
|
||||
wrapping as outlined in the <a href="overloading.html">
|
||||
previous section</a>, or
|
||||
writing thin wrappers:</p>
|
||||
<code><pre>
|
||||
<span class=comment>// write "thin wrappers"
|
||||
</span><span class=keyword>int </span><span class=identifier>f1</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>x</span><span class=special>) { </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>x</span><span class=special>); }
|
||||
</span><span class=keyword>int </span><span class=identifier>f2</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>x</span><span class=special>, </span><span class=keyword>double </span><span class=identifier>y</span><span class=special>) { </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>x</span><span class=special>,</span><span class=identifier>y</span><span class=special>); }
|
||||
|
||||
/*...*/
|
||||
|
||||
// </span><span class=identifier>in </span><span class=identifier>module </span><span class=identifier>init
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>f</span><span class=special>); // </span><span class=identifier>all </span><span class=identifier>arguments
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>f2</span><span class=special>); // </span><span class=identifier>two </span><span class=identifier>arguments
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>f1</span><span class=special>); // </span><span class=identifier>one </span><span class=identifier>argument
|
||||
</span></pre></code>
|
||||
<p>
|
||||
When you want to wrap functions (or member functions) that either:</p>
|
||||
<ul><li>have default arguments, or</li><li>are overloaded with a common sequence of initial arguments</li></ul><a name="boost_python_function_overloads"></a><h2>BOOST_PYTHON_FUNCTION_OVERLOADS</h2><p>
|
||||
Boost.Python now has a way to make it easier. For instance, given a function:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>int </span><span class=identifier>foo</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>char </span><span class=identifier>b </span><span class=special>= </span><span class=number>1</span><span class=special>, </span><span class=keyword>unsigned </span><span class=identifier>c </span><span class=special>= </span><span class=number>2</span><span class=special>, </span><span class=keyword>double </span><span class=identifier>d </span><span class=special>= </span><span class=number>3</span><span class=special>)
|
||||
{
|
||||
/*...*/
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The macro invocation:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>BOOST_PYTHON_FUNCTION_OVERLOADS</span><span class=special>(</span><span class=identifier>foo_overloads</span><span class=special>, </span><span class=identifier>foo</span><span class=special>, </span><span class=number>1</span><span class=special>, </span><span class=number>4</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
will automatically create the thin wrappers for us. This macro will create
|
||||
a class <tt>foo_overloads</tt> that can be passed on to <tt>def(...)</tt>. The third
|
||||
and fourth macro argument are the minimum arguments and maximum arguments,
|
||||
respectively. In our <tt>foo</tt> function the minimum number of arguments is 1
|
||||
and the maximum number of arguments is 4. The <tt>def(...)</tt> function will
|
||||
automatically add all the foo variants for us:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>def</span><span class=special>(</span><span class=string>"foo"</span><span class=special>, </span><span class=identifier>foo</span><span class=special>, </span><span class=identifier>foo_overloads</span><span class=special>());
|
||||
</span></pre></code>
|
||||
<a name="boost_python_member_function_overloads"></a><h2>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</h2><p>
|
||||
Objects here, objects there, objects here there everywhere. More frequently
|
||||
than anything else, we need to expose member functions of our classes to
|
||||
Python. Then again, we have the same inconveniences as before when default
|
||||
arguments or overloads with a common sequence of initial arguments come
|
||||
into play. Another macro is provided to make this a breeze.</p>
|
||||
<p>
|
||||
Like <tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt>,
|
||||
<tt>BOOST_PYTHON_FUNCTION_OVERLOADS</tt> may be used to automatically create
|
||||
the thin wrappers for wrapping member functions. Let's have an example:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>george
|
||||
</span><span class=special>{
|
||||
</span><span class=keyword>void
|
||||
</span><span class=identifier>wack_em</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>b </span><span class=special>= </span><span class=number>0</span><span class=special>, </span><span class=keyword>char </span><span class=identifier>c </span><span class=special>= </span><span class=literal>'x'</span><span class=special>)
|
||||
{
|
||||
/*...*/
|
||||
}
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The macro invocation:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS</span><span class=special>(</span><span class=identifier>george_overloads</span><span class=special>, </span><span class=identifier>wack_em</span><span class=special>, </span><span class=number>1</span><span class=special>, </span><span class=number>3</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
will generate a set of thin wrappers for george's <tt>wack_em</tt> member function
|
||||
accepting a minimum of 1 and a maximum of 3 arguments (i.e. the third and
|
||||
fourth macro argument). The thin wrappers are all enclosed in a class named
|
||||
<tt>george_overloads</tt> that can then be used as an argument to <tt>def(...)</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"wack_em"</span><span class=special>, &</span><span class=identifier>george</span><span class=special>::</span><span class=identifier>wack_em</span><span class=special>, </span><span class=identifier>george_overloads</span><span class=special>());
|
||||
</span></pre></code>
|
||||
<p>
|
||||
See the <a href="../../v2/overloads.html#BOOST_PYTHON_FUNCTION_OVERLOADS-spec">
|
||||
overloads reference</a>
|
||||
for details.</p>
|
||||
<a name="init_and_optional"></a><h2>init and optional</h2><p>
|
||||
A similar facility is provided for class constructors, again, with
|
||||
default arguments or a sequence of overloads. Remember <tt>init<...></tt>? For example,
|
||||
given a class X with a constructor:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>X
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>X</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>char </span><span class=identifier>b </span><span class=special>= </span><span class=literal>'D'</span><span class=special>, </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>c </span><span class=special>= </span><span class=string>"constructor"</span><span class=special>, </span><span class=keyword>double </span><span class=identifier>d </span><span class=special>= </span><span class=number>0.0</span><span class=special>);
|
||||
/*...*/
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
You can easily add this constructor to Boost.Python in one shot:</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=identifier>init</span><span class=special><</span><span class=keyword>int</span><span class=special>, </span><span class=identifier>optional</span><span class=special><</span><span class=keyword>char</span><span class=special>, </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>, </span><span class=keyword>double</span><span class=special>> >())
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Notice the use of <tt>init<...></tt> and <tt>optional<...></tt> to signify the default
|
||||
(optional arguments).</p>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="overloading.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="auto_overloading.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,117 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Derived Object types</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="basic_interface.html">
|
||||
<link rel="next" href="extracting_c___objects.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Derived Object types</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="basic_interface.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="extracting_c___objects.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Boost.Python comes with a set of derived <tt>object</tt> types corresponding to
|
||||
that of Python's:</p>
|
||||
<ul><li>list</li><li>dict</li><li>tuple</li><li>str</li><li>long_</li><li>enum</li></ul><p>
|
||||
These derived <tt>object</tt> types act like real Python types. For instance:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>str</span><span class=special>(</span><span class=number>1</span><span class=special>) ==> </span><span class=string>"1"
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Wherever appropriate, a particular derived <tt>object</tt> has corresponding
|
||||
Python type's methods. For instance, <tt>dict</tt> has a <tt>keys()</tt> method:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>d</span><span class=special>.</span><span class=identifier>keys</span><span class=special>()
|
||||
</span></pre></code>
|
||||
<p>
|
||||
<tt>make_tuple</tt> is provided for declaring <i>tuple literals</i>. Example:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>make_tuple</span><span class=special>(</span><span class=number>123</span><span class=special>, </span><span class=literal>'D'</span><span class=special>, </span><span class=string>"Hello, World"</span><span class=special>, </span><span class=number>0.0</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
In C++, when Boost.Python <tt>object</tt>s are used as arguments to functions,
|
||||
subtype matching is required. For example, when a function <tt>f</tt>, as
|
||||
declared below, is wrapped, it will only accept instances of Python's
|
||||
<tt>str</tt> type and subtypes.</p>
|
||||
<code><pre>
|
||||
<span class=keyword>void </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>str </span><span class=identifier>name</span><span class=special>)
|
||||
{
|
||||
</span><span class=identifier>object </span><span class=identifier>n2 </span><span class=special>= </span><span class=identifier>name</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"upper"</span><span class=special>)(); // </span><span class=identifier>NAME </span><span class=special>= </span><span class=identifier>name</span><span class=special>.</span><span class=identifier>upper</span><span class=special>()
|
||||
</span><span class=identifier>str </span><span class=identifier>NAME </span><span class=special>= </span><span class=identifier>name</span><span class=special>.</span><span class=identifier>upper</span><span class=special>(); // </span><span class=identifier>better
|
||||
</span><span class=identifier>object </span><span class=identifier>msg </span><span class=special>= </span><span class=string>"%s is bigger than %s" </span><span class=special>% </span><span class=identifier>make_tuple</span><span class=special>(</span><span class=identifier>NAME</span><span class=special>,</span><span class=identifier>name</span><span class=special>);
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
In finer detail:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>str </span><span class=identifier>NAME </span><span class=special>= </span><span class=identifier>name</span><span class=special>.</span><span class=identifier>upper</span><span class=special>();
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Illustrates that we provide versions of the str type's methods as C++
|
||||
member functions.</p>
|
||||
<code><pre>
|
||||
<span class=identifier>object </span><span class=identifier>msg </span><span class=special>= </span><span class=string>"%s is bigger than %s" </span><span class=special>% </span><span class=identifier>make_tuple</span><span class=special>(</span><span class=identifier>NAME</span><span class=special>,</span><span class=identifier>name</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Demonstrates that you can write the C++ equivalent of <tt>"format" % x,y,z</tt>
|
||||
in Python, which is useful since there's no easy way to do that in std C++.</p>
|
||||
<p>
|
||||
<img src="theme/alert.gif"></img> <b>Beware</b> the common pitfall of forgetting that the constructors
|
||||
of most of Python's mutable types make copies, just as in Python.</p>
|
||||
<p>
|
||||
Python:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>d </span><span class=special>= </span><span class=identifier>dict</span><span class=special>(</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>__dict__</span><span class=special>) </span>##<span class=identifier>copies </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>__dict__
|
||||
</span><span class=special>>>> </span><span class=identifier>d</span><span class=special>[</span><span class=literal>'whatever'</span><span class=special>] </span>##<span class=identifier>modifies </span><span class=identifier>the </span><span class=identifier>copy
|
||||
</span></pre></code>
|
||||
<p>
|
||||
C++:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>dict </span><span class=identifier>d</span><span class=special>(</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"__dict__"</span><span class=special>)); </span>##<span class=identifier>copies </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>__dict__
|
||||
</span><span class=identifier>d</span><span class=special>[</span><span class=literal>'whatever'</span><span class=special>] = </span><span class=number>3</span><span class=special>; </span>##<span class=identifier>modifies </span><span class=identifier>the </span><span class=identifier>copy
|
||||
</span></pre></code>
|
||||
<a name="class__lt_t_gt__as_objects"></a><h2>class_<T> as objects</h2><p>
|
||||
Due to the dynamic nature of Boost.Python objects, any <tt>class_<T></tt> may
|
||||
also be one of these types! The following code snippet wraps the class
|
||||
(type) object.</p>
|
||||
<p>
|
||||
We can use this to create wrapped instances. Example:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>object </span><span class=identifier>vec345 </span><span class=special>= (
|
||||
</span><span class=identifier>class_</span><span class=special><</span><span class=identifier>Vec2</span><span class=special>>(</span><span class=string>"Vec2"</span><span class=special>, </span><span class=identifier>init</span><span class=special><</span><span class=keyword>double</span><span class=special>, </span><span class=keyword>double</span><span class=special>>())
|
||||
.</span><span class=identifier>def_readonly</span><span class=special>(</span><span class=string>"length"</span><span class=special>, &</span><span class=identifier>Point</span><span class=special>::</span><span class=identifier>length</span><span class=special>)
|
||||
.</span><span class=identifier>def_readonly</span><span class=special>(</span><span class=string>"angle"</span><span class=special>, &</span><span class=identifier>Point</span><span class=special>::</span><span class=identifier>angle</span><span class=special>)
|
||||
)(</span><span class=number>3.0</span><span class=special>, </span><span class=number>4.0</span><span class=special>);
|
||||
|
||||
</span><span class=identifier>assert</span><span class=special>(</span><span class=identifier>vec345</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"length"</span><span class=special>) == </span><span class=number>5.0</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="basic_interface.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="extracting_c___objects.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,83 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Deriving a Python Class</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="class_virtual_functions.html">
|
||||
<link rel="next" href="virtual_functions_with_default_implementations.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Deriving a Python Class</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_virtual_functions.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="virtual_functions_with_default_implementations.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Continuing, we can derive from our base class Base in Python and override
|
||||
the virtual function in Python. Before we can do that, we have to set up
|
||||
our <tt>class_</tt> wrapper as:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Base</span><span class=special>, </span><span class=identifier>BaseWrap</span><span class=special>, </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>noncopyable</span><span class=special>>(</span><span class=string>"Base"</span><span class=special>)
|
||||
;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Otherwise, we have to suppress the Base class' <tt>no_init</tt> by adding an
|
||||
<tt>__init__()</tt> method to all our derived classes. <tt>no_init</tt> actually adds
|
||||
an <tt>__init__</tt> method that raises a Python RuntimeError exception.</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=keyword>class </span><span class=identifier>Derived</span><span class=special>(</span><span class=identifier>Base</span><span class=special>):
|
||||
... </span><span class=identifier>def </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>self</span><span class=special>):
|
||||
... </span><span class=keyword>return </span><span class=number>42
|
||||
</span><span class=special>...
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Cool eh? A Python class deriving from a C++ class!</p>
|
||||
<p>
|
||||
Let's now make an instance of our Python class <tt>Derived</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>derived </span><span class=special>= </span><span class=identifier>Derived</span><span class=special>()
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Calling <tt>derived.f()</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>derived</span><span class=special>.</span><span class=identifier>f</span><span class=special>()
|
||||
</span><span class=number>42
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Will yield the expected result. Finally, calling calling the free function
|
||||
<tt>call_f</tt> with <tt>derived</tt> as argument:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>call_f</span><span class=special>(</span><span class=identifier>derived</span><span class=special>)
|
||||
</span><span class=number>42
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Will also yield the expected result.</p>
|
||||
<p>
|
||||
Here's what's happening:</p>
|
||||
<ol><li><tt>call_f(derived)</tt> is called in Python</li><li>This corresponds to <tt>def("call_f", call_f);</tt>. Boost.Python dispatches this call.</li><li><tt>int call_f(Base& b) { return b.f(); }</tt> accepts the call.</li><li>The overridden virtual function <tt>f</tt> of <tt>BaseWrap</tt> is called.</li><li><tt>call_method<int>(self, "f");</tt> dispatches the call back to Python.</li><li><tt>def f(self): return 42</tt> is finally called.</li></ol><table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_virtual_functions.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="virtual_functions_with_default_implementations.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,97 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Embedding</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="enums.html">
|
||||
<link rel="next" href="using_the_interpreter.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Embedding</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="enums.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="using_the_interpreter.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
By now you should know how to use Boost.Python to call your C++ code from
|
||||
Python. However, sometimes you may need to do the reverse: call Python code
|
||||
from the C++-side. This requires you to <i>embed</i> the Python interpreter
|
||||
into your C++ program.</p>
|
||||
<p>
|
||||
Currently, Boost.Python does not directly support everything you'll need
|
||||
when embedding. Therefore you'll need to use the
|
||||
<a href="http://www.python.org/doc/current/api/api.html">
|
||||
Python/C API</a> to fill in
|
||||
the gaps. However, Boost.Python already makes embedding a lot easier and,
|
||||
in a future version, it may become unnecessary to touch the Python/C API at
|
||||
all. So stay tuned... <img src="theme/smiley.gif"></img></p>
|
||||
<a name="building_embedded_programs"></a><h2>Building embedded programs</h2><p>
|
||||
To be able to use embedding in your programs, they have to be linked to
|
||||
both Boost.Python's and Python's static link library.</p>
|
||||
<p>
|
||||
Boost.Python's static link library comes in two variants. Both are located
|
||||
in Boost's <tt>/libs/python/build/bin-stage</tt> subdirectory. On Windows, the
|
||||
variants are called <tt>boost_python.lib</tt> (for release builds) and
|
||||
<tt>boost_python_debug.lib</tt> (for debugging). If you can't find the
|
||||
libraries, you probably haven't built Boost.Python yet. See <a
|
||||
href="../../building.html">Building and Testing</a> on how to do
|
||||
this.</p>
|
||||
<p>
|
||||
Python's static link library can be found in the <tt>/libs</tt> subdirectory of
|
||||
your Python directory. On Windows it is called pythonXY.lib where X.Y is
|
||||
your major Python version number.</p>
|
||||
<p>
|
||||
Additionally, Python's <tt>/include</tt> subdirectory has to be added to your
|
||||
include path.</p>
|
||||
<p>
|
||||
In a Jamfile, all the above boils down to:</p>
|
||||
<code><pre>
|
||||
projectroot c:\projects\embedded_program ; # location of the program
|
||||
|
||||
# bring in the rules for python
|
||||
SEARCH on python.jam = $(BOOST_BUILD_PATH) ;
|
||||
include python.jam ;
|
||||
|
||||
exe embedded_program # name of the executable
|
||||
: #sources
|
||||
embedded_program.cpp
|
||||
: # requirements
|
||||
<find-library>boost_python <library-path>c:\boost\libs\python
|
||||
$(PYTHON_PROPERTIES)
|
||||
<library-path>$(PYTHON_LIB_PATH)
|
||||
<find-library>$(PYTHON_EMBEDDED_LIBRARY) ;
|
||||
</pre></code><a name="getting_started"></a><h2>Getting started</h2><p>
|
||||
Being able to build is nice, but there is nothing to build yet. Embedding
|
||||
the Python interpreter into one of your C++ programs requires these 4
|
||||
steps:</p>
|
||||
<ol><li>#include <tt><boost/python.hpp></tt><br><br></li><li>Call <a href="http://www.python.org/doc/current/api/initialization.html#l2h-652">
|
||||
Py_Initialize</a>() to start the interpreter and create the <tt>__main__</tt> module.<br><br></li><li>Call other Python C API routines to use the interpreter.<br><br></li><li>Call <a href="http://www.python.org/doc/current/api/initialization.html#l2h-656">
|
||||
Py_Finalize</a>() to stop the interpreter and release its resources.</li></ol><p>
|
||||
(Of course, there can be other C++ code between all of these steps.)</p>
|
||||
<blockquote><p><i><b>Now that we can embed the interpreter in our programs, lets see how to put it to use...</b></i></p></blockquote><table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="enums.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="using_the_interpreter.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 Dirk Gerrits<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,95 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Enums</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="extracting_c___objects.html">
|
||||
<link rel="next" href="embedding.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Enums</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="extracting_c___objects.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="embedding.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Boost.Python has a nifty facility to capture and wrap C++ enums. While
|
||||
Python has no <tt>enum</tt> type, we'll often want to expose our C++ enums to
|
||||
Python as an <tt>int</tt>. Boost.Python's enum facility makes this easy while
|
||||
taking care of the proper conversions from Python's dynamic typing to C++'s
|
||||
strong static typing (in C++, ints cannot be implicitly converted to
|
||||
enums). To illustrate, given a C++ enum:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>enum </span><span class=identifier>choice </span><span class=special>{ </span><span class=identifier>red</span><span class=special>, </span><span class=identifier>blue </span><span class=special>};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
the construct:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>enum_</span><span class=special><</span><span class=identifier>choice</span><span class=special>>(</span><span class=string>"choice"</span><span class=special>)
|
||||
.</span><span class=identifier>value</span><span class=special>(</span><span class=string>"red"</span><span class=special>, </span><span class=identifier>red</span><span class=special>)
|
||||
.</span><span class=identifier>value</span><span class=special>(</span><span class=string>"blue"</span><span class=special>, </span><span class=identifier>blue</span><span class=special>)
|
||||
;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
can be used to expose to Python. The new enum type is created in the
|
||||
current <tt>scope()</tt>, which is usually the current module. The snippet above
|
||||
creates a Python class derived from Python's <tt>int</tt> type which is
|
||||
associated with the C++ type passed as its first parameter.</p>
|
||||
<table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<img src="theme/lens.gif"></img> <b>what is a scope?</b><br><br> The scope is a class that has an
|
||||
associated global Python object which controls the Python namespace in
|
||||
which new extension classes and wrapped functions will be defined as
|
||||
attributes. Details can be found <a href="../../v2/scope.html">
|
||||
here</a>. </td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
You can access those values in Python as</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>my_module</span><span class=special>.</span><span class=identifier>choice</span><span class=special>.</span><span class=identifier>red
|
||||
</span><span class=identifier>my_module</span><span class=special>.</span><span class=identifier>choice</span><span class=special>.</span><span class=identifier>red
|
||||
</span></pre></code>
|
||||
<p>
|
||||
where my_module is the module where the enum is declared. You can also
|
||||
create a new scope around a class:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>scope </span><span class=identifier>in_X </span><span class=special>= </span><span class=identifier>class_</span><span class=special><</span><span class=identifier>X</span><span class=special>>(</span><span class=string>"X"</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>( ... )
|
||||
.</span><span class=identifier>def</span><span class=special>( ... )
|
||||
;
|
||||
|
||||
// </span><span class=identifier>Expose </span><span class=identifier>X</span><span class=special>::</span><span class=identifier>nested </span><span class=identifier>as </span><span class=identifier>X</span><span class=special>.</span><span class=identifier>nested
|
||||
</span><span class=identifier>enum_</span><span class=special><</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>nested</span><span class=special>>(</span><span class=string>"nested"</span><span class=special>)
|
||||
.</span><span class=identifier>value</span><span class=special>(</span><span class=string>"red"</span><span class=special>, </span><span class=identifier>red</span><span class=special>)
|
||||
.</span><span class=identifier>value</span><span class=special>(</span><span class=string>"blue"</span><span class=special>, </span><span class=identifier>blue</span><span class=special>)
|
||||
;
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="extracting_c___objects.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="embedding.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,60 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Exception Translation</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="iterators.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Exception Translation</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="iterators.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><img src="theme/r_arr_disabled.gif" border="0"></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
All C++ exceptions must be caught at the boundary with Python code. This
|
||||
boundary is the point where C++ meets Python. Boost.Python provides a
|
||||
default exception handler that translates selected standard exceptions,
|
||||
then gives up:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>raise </span><span class=identifier>RuntimeError</span><span class=special>, </span><span class=literal>'unidentifiable C++ Exception'
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Users may provide custom translation. Here's an example:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>PodBayDoorException</span><span class=special>;
|
||||
</span><span class=keyword>void </span><span class=identifier>translator</span><span class=special>(</span><span class=identifier>PodBayDoorException </span><span class=keyword>const</span><span class=special>& </span><span class=identifier>x</span><span class=special>) {
|
||||
</span><span class=identifier>PyErr_SetString</span><span class=special>(</span><span class=identifier>PyExc_UserWarning</span><span class=special>, </span><span class=string>"I'm sorry Dave..."</span><span class=special>);
|
||||
}
|
||||
</span><span class=identifier>BOOST_PYTHON_MODULE</span><span class=special>(</span><span class=identifier>kubrick</span><span class=special>) {
|
||||
</span><span class=identifier>register_exception_translator</span><span class=special><
|
||||
</span><span class=identifier>PodBayDoorException</span><span class=special>>(</span><span class=identifier>translator</span><span class=special>);
|
||||
...
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="iterators.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><img src="theme/r_arr_disabled.gif" border="0"></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,79 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Exposing Classes</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="building_hello_world.html">
|
||||
<link rel="next" href="constructors.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Exposing Classes</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="building_hello_world.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="constructors.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Now let's expose a C++ class to Python.</p>
|
||||
<p>
|
||||
Consider a C++ class/struct that we want to expose to Python:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>World
|
||||
</span><span class=special>{
|
||||
</span><span class=keyword>void </span><span class=identifier>set</span><span class=special>(</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>) { </span><span class=keyword>this</span><span class=special>-></span><span class=identifier>msg </span><span class=special>= </span><span class=identifier>msg</span><span class=special>; }
|
||||
</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>greet</span><span class=special>() { </span><span class=keyword>return </span><span class=identifier>msg</span><span class=special>; }
|
||||
</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
We can expose this to Python by writing a corresponding Boost.Python
|
||||
C++ Wrapper:</p>
|
||||
<code><pre>
|
||||
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>python</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
|
||||
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>python</span><span class=special>;
|
||||
|
||||
</span><span class=identifier>BOOST_PYTHON_MODULE</span><span class=special>(</span><span class=identifier>hello</span><span class=special>)
|
||||
{
|
||||
</span><span class=identifier>class_</span><span class=special><</span><span class=identifier>World</span><span class=special>>(</span><span class=string>"World"</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"greet"</span><span class=special>, &</span><span class=identifier>World</span><span class=special>::</span><span class=identifier>greet</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"set"</span><span class=special>, &</span><span class=identifier>World</span><span class=special>::</span><span class=identifier>set</span><span class=special>)
|
||||
;
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Here, we wrote a C++ class wrapper that exposes the member functions
|
||||
<tt>greet</tt> and <tt>set</tt>. Now, after building our module as a shared library, we
|
||||
may use our class <tt>World</tt> in Python. Here's a sample Python session:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>import </span><span class=identifier>hello
|
||||
</span><span class=special>>>> </span><span class=identifier>planet </span><span class=special>= </span><span class=identifier>hello</span><span class=special>.</span><span class=identifier>World</span><span class=special>()
|
||||
>>> </span><span class=identifier>planet</span><span class=special>.</span><span class=identifier>set</span><span class=special>(</span><span class=literal>'howdy'</span><span class=special>)
|
||||
>>> </span><span class=identifier>planet</span><span class=special>.</span><span class=identifier>greet</span><span class=special>()
|
||||
</span><span class=literal>'howdy'
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="building_hello_world.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="constructors.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,79 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Extracting C++ objects</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="derived_object_types.html">
|
||||
<link rel="next" href="enums.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Extracting C++ objects</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="derived_object_types.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="enums.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
At some point, we will need to get C++ values out of object instances. This
|
||||
can be achieved with the <tt>extract<T></tt> function. Consider the following:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>double </span><span class=identifier>x </span><span class=special>= </span><span class=identifier>o</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"length"</span><span class=special>); // </span><span class=identifier>compile </span><span class=identifier>error
|
||||
</span></pre></code>
|
||||
<p>
|
||||
In the code above, we got a compiler error because Boost.Python
|
||||
<tt>object</tt> can't be implicitly converted to <tt>double</tt>s. Instead, what
|
||||
we wanted to do above can be achieved by writing:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>double </span><span class=identifier>l </span><span class=special>= </span><span class=identifier>extract</span><span class=special><</span><span class=keyword>double</span><span class=special>>(</span><span class=identifier>o</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"length"</span><span class=special>));
|
||||
</span><span class=identifier>Vec2</span><span class=special>& </span><span class=identifier>v </span><span class=special>= </span><span class=identifier>extract</span><span class=special><</span><span class=identifier>Vec2</span><span class=special>&>(</span><span class=identifier>o</span><span class=special>);
|
||||
</span><span class=identifier>assert</span><span class=special>(</span><span class=identifier>l </span><span class=special>== </span><span class=identifier>v</span><span class=special>.</span><span class=identifier>length</span><span class=special>());
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The first line attempts to extract the "length" attribute of the
|
||||
Boost.Python <tt>object</tt> <tt>o</tt>. The second line attempts to <i>extract</i> the
|
||||
<tt>Vec2</tt> object from held by the Boost.Python <tt>object</tt> <tt>o</tt>.</p>
|
||||
<p>
|
||||
Take note that we said "attempt to" above. What if the Boost.Python
|
||||
<tt>object</tt> <tt>o</tt> does not really hold a <tt>Vec2</tt> type? This is certainly
|
||||
a possibility considering the dynamic nature of Python <tt>object</tt>s. To
|
||||
be on the safe side, if the C++ type can't be extracted, an
|
||||
appropriate exception is thrown. To avoid an exception, we need to
|
||||
test for extractibility:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>extract</span><span class=special><</span><span class=identifier>Vec2</span><span class=special>&> </span><span class=identifier>x</span><span class=special>(</span><span class=identifier>o</span><span class=special>);
|
||||
</span><span class=keyword>if </span><span class=special>(</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>check</span><span class=special>()) {
|
||||
</span><span class=identifier>Vec2</span><span class=special>& </span><span class=identifier>v </span><span class=special>= </span><span class=identifier>x</span><span class=special>(); ...
|
||||
</span></pre></code>
|
||||
<p>
|
||||
<img src="theme/bulb.gif"></img> The astute reader might have noticed that the <tt>extract<T></tt>
|
||||
facility in fact solves the mutable copying problem:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>dict </span><span class=identifier>d </span><span class=special>= </span><span class=identifier>extract</span><span class=special><</span><span class=identifier>dict</span><span class=special>>(</span><span class=identifier>x</span><span class=special>.</span><span class=identifier>attr</span><span class=special>(</span><span class=string>"__dict__"</span><span class=special>));
|
||||
</span><span class=identifier>d</span><span class=special>[</span><span class=literal>'whatever'</span><span class=special>] = </span><span class=number>3</span><span class=special>; </span>##<span class=identifier>modifies </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>__dict__ </span><span class=special>!
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="derived_object_types.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="enums.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,73 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Functions</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="class_operators_special_functions.html">
|
||||
<link rel="next" href="call_policies.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Functions</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_operators_special_functions.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="call_policies.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
In this chapter, we'll look at Boost.Python powered functions in closer
|
||||
detail. We shall see some facilities to make exposing C++ functions to
|
||||
Python safe from potential pifalls such as dangling pointers and
|
||||
references. We shall also see facilities that will make it even easier for
|
||||
us to expose C++ functions that take advantage of C++ features such as
|
||||
overloading and default arguments.</p>
|
||||
<blockquote><p><i>Read on...</i></p></blockquote><p>
|
||||
But before you do, you might want to fire up Python 2.2 or later and type
|
||||
<tt>>>> import this</tt>.</p>
|
||||
<code><pre>
|
||||
>>> import this
|
||||
The Zen of Python, by Tim Peters
|
||||
Beautiful is better than ugly.
|
||||
Explicit is better than implicit.
|
||||
Simple is better than complex.
|
||||
Complex is better than complicated.
|
||||
Flat is better than nested.
|
||||
Sparse is better than dense.
|
||||
Readability counts.
|
||||
Special cases aren't special enough to break the rules.
|
||||
Although practicality beats purity.
|
||||
Errors should never pass silently.
|
||||
Unless explicitly silenced.
|
||||
In the face of ambiguity, refuse the temptation to guess.
|
||||
There should be one-- and preferably only one --obvious way to do it
|
||||
Although that way may not be obvious at first unless you're Dutch.
|
||||
Now is better than never.
|
||||
Although never is often better than *right* now.
|
||||
If the implementation is hard to explain, it's a bad idea.
|
||||
If the implementation is easy to explain, it may be a good idea.
|
||||
Namespaces are one honking great idea -- let's do more of those!
|
||||
</pre></code><table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_operators_special_functions.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="call_policies.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,98 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Inheritance</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="class_properties.html">
|
||||
<link rel="next" href="class_virtual_functions.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Inheritance</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_properties.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_virtual_functions.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
In the previous examples, we dealt with classes that are not polymorphic.
|
||||
This is not often the case. Much of the time, we will be wrapping
|
||||
polymorphic classes and class hierarchies related by inheritance. We will
|
||||
often have to write Boost.Python wrappers for classes that are derived from
|
||||
abstract base classes.</p>
|
||||
<p>
|
||||
Consider this trivial inheritance structure:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Base </span><span class=special>{ </span><span class=keyword>virtual </span><span class=special>~</span><span class=identifier>Base</span><span class=special>(); };
|
||||
</span><span class=keyword>struct </span><span class=identifier>Derived </span><span class=special>: </span><span class=identifier>Base </span><span class=special>{};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
And a set of C++ functions operating on <tt>Base</tt> and <tt>Derived</tt> object
|
||||
instances:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>void </span><span class=identifier>b</span><span class=special>(</span><span class=identifier>Base</span><span class=special>*);
|
||||
</span><span class=keyword>void </span><span class=identifier>d</span><span class=special>(</span><span class=identifier>Derived</span><span class=special>*);
|
||||
</span><span class=identifier>Base</span><span class=special>* </span><span class=identifier>factory</span><span class=special>() { </span><span class=keyword>return </span><span class=keyword>new </span><span class=identifier>Derived</span><span class=special>; }
|
||||
</span></pre></code>
|
||||
<p>
|
||||
We've seen how we can wrap the base class <tt>Base</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Base</span><span class=special>>(</span><span class=string>"Base"</span><span class=special>)
|
||||
/*...*/
|
||||
;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Now we can inform Boost.Python of the inheritance relationship between
|
||||
<tt>Derived</tt> and its base class <tt>Base</tt>. Thus:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Derived</span><span class=special>, </span><span class=identifier>bases</span><span class=special><</span><span class=identifier>Base</span><span class=special>> >(</span><span class=string>"Derived"</span><span class=special>)
|
||||
/*...*/
|
||||
;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Doing so, we get some things for free:</p>
|
||||
<ol><li>Derived automatically inherits all of Base's Python methods (wrapped C++ member functions)</li><li><b>If</b> Base is polymorphic, <tt>Derived</tt> objects which have been passed to Python via a pointer or reference to <tt>Base</tt> can be passed where a pointer or reference to <tt>Derived</tt> is expected.</li></ol><p>
|
||||
Now, we shall expose the C++ free functions <tt>b</tt> and <tt>d</tt> and <tt>factory</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>def</span><span class=special>(</span><span class=string>"b"</span><span class=special>, </span><span class=identifier>b</span><span class=special>);
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"d"</span><span class=special>, </span><span class=identifier>d</span><span class=special>);
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"factory"</span><span class=special>, </span><span class=identifier>factory</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Note that free function <tt>factory</tt> is being used to generate new
|
||||
instances of class <tt>Derived</tt>. In such cases, we use
|
||||
<tt>return_value_policy<manage_new_object></tt> to instruct Python to adopt
|
||||
the pointer to <tt>Base</tt> and hold the instance in a new Python <tt>Base</tt>
|
||||
object until the the Python object is destroyed. We shall see more of
|
||||
Boost.Python <a href="call_policies.html">
|
||||
call policies</a> later.</p>
|
||||
<code><pre>
|
||||
<span class=comment>// Tell Python to take ownership of factory's result
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"factory"</span><span class=special>, </span><span class=identifier>factory</span><span class=special>,
|
||||
</span><span class=identifier>return_value_policy</span><span class=special><</span><span class=identifier>manage_new_object</span><span class=special>>());
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="class_properties.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_virtual_functions.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,101 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Iterators</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="using_the_interpreter.html">
|
||||
<link rel="next" href="exception_translation.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Iterators</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="using_the_interpreter.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="exception_translation.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
In C++, and STL in particular, we see iterators everywhere. Python also has
|
||||
iterators, but these are two very different beasts.</p>
|
||||
<p>
|
||||
<b>C++ iterators:</b></p>
|
||||
<ul><li>C++ has 5 type categories (random-access, bidirectional, forward, input, output)</li><li>There are 2 Operation categories: reposition, access</li><li>A pair of iterators is needed to represent a (first/last) range.</li></ul><p>
|
||||
<b>Python Iterators:</b></p>
|
||||
<ul><li>1 category (forward)</li><li>1 operation category (next())</li><li>Raises StopIteration exception at end</li></ul><p>
|
||||
The typical Python iteration protocol: <tt><b>for y in x...</b></tt> is as follows:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>iter </span><span class=special>= </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>__iter__</span><span class=special>() </span>##<span class=identifier>get </span><span class=identifier>iterator
|
||||
</span><span class=keyword>try</span><span class=special>:
|
||||
</span><span class=keyword>while </span><span class=number>1</span><span class=special>:
|
||||
</span><span class=identifier>y </span><span class=special>= </span><span class=identifier>iter</span><span class=special>.</span><span class=identifier>next</span><span class=special>() </span>##<span class=identifier>get </span><span class=identifier>each </span><span class=identifier>item
|
||||
</span><span class=special>... </span>##<span class=identifier>process </span><span class=identifier>y
|
||||
</span><span class=identifier>except </span><span class=identifier>StopIteration</span><span class=special>: </span><span class=identifier>pass </span>##<span class=identifier>iterator </span><span class=identifier>exhausted
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Boost.Python provides some mechanisms to make C++ iterators play along
|
||||
nicely as Python iterators. What we need to do is to produce
|
||||
appropriate __iter__ function from C++ iterators that is compatible
|
||||
with the Python iteration protocol. For example:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>object </span><span class=identifier>get_iterator </span><span class=special>= </span><span class=identifier>iterator</span><span class=special><</span><span class=identifier>vector</span><span class=special><</span><span class=keyword>int</span><span class=special>> >();
|
||||
</span><span class=identifier>object </span><span class=identifier>iter </span><span class=special>= </span><span class=identifier>get_iterator</span><span class=special>(</span><span class=identifier>v</span><span class=special>);
|
||||
</span><span class=identifier>object </span><span class=identifier>first </span><span class=special>= </span><span class=identifier>iter</span><span class=special>.</span><span class=identifier>next</span><span class=special>();
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Or for use in class_<>:</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"__iter__"</span><span class=special>, </span><span class=identifier>iterator</span><span class=special><</span><span class=identifier>vector</span><span class=special><</span><span class=keyword>int</span><span class=special>> >())
|
||||
</span></pre></code>
|
||||
<p>
|
||||
<b>range</b></p>
|
||||
<p>
|
||||
We can create a Python savvy iterator using the range function:</p>
|
||||
<ul><li>range(start, finish)</li><li>range<Policies,Target>(start, finish)</li></ul><p>
|
||||
Here, start/finish may be one of:</p>
|
||||
<ul><li>member data pointers</li><li>member function pointers</li><li>adaptable function object (use Target parameter)</li></ul><p>
|
||||
<b>iterator</b></p>
|
||||
<ul><li>iterator<T, Policies>()</li></ul><p>
|
||||
Given a container <tt>T</tt>, iterator is a shortcut that simply calls <tt>range</tt>
|
||||
with &T::begin, &T::end.</p>
|
||||
<p>
|
||||
Let's put this into action... Here's an example from some hypothetical
|
||||
bogon Particle accelerator code:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>f </span><span class=special>= </span><span class=identifier>Field</span><span class=special>()
|
||||
</span><span class=keyword>for </span><span class=identifier>x </span><span class=identifier>in </span><span class=identifier>f</span><span class=special>.</span><span class=identifier>pions</span><span class=special>:
|
||||
</span><span class=identifier>smash</span><span class=special>(</span><span class=identifier>x</span><span class=special>)
|
||||
</span><span class=keyword>for </span><span class=identifier>y </span><span class=identifier>in </span><span class=identifier>f</span><span class=special>.</span><span class=identifier>bogons</span><span class=special>:
|
||||
</span><span class=identifier>count</span><span class=special>(</span><span class=identifier>y</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Now, our C++ Wrapper:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>F</span><span class=special>>(</span><span class=string>"Field"</span><span class=special>)
|
||||
.</span><span class=identifier>property</span><span class=special>(</span><span class=string>"pions"</span><span class=special>, </span><span class=identifier>range</span><span class=special>(&</span><span class=identifier>F</span><span class=special>::</span><span class=identifier>p_begin</span><span class=special>, &</span><span class=identifier>F</span><span class=special>::</span><span class=identifier>p_end</span><span class=special>))
|
||||
.</span><span class=identifier>property</span><span class=special>(</span><span class=string>"bogons"</span><span class=special>, </span><span class=identifier>range</span><span class=special>(&</span><span class=identifier>F</span><span class=special>::</span><span class=identifier>b_begin</span><span class=special>, &</span><span class=identifier>F</span><span class=special>::</span><span class=identifier>b_end</span><span class=special>));
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="using_the_interpreter.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="exception_translation.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,54 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Object Interface</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="auto_overloading.html">
|
||||
<link rel="next" href="basic_interface.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Object Interface</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="auto_overloading.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="basic_interface.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Python is dynamically typed, unlike C++ which is statically typed. Python
|
||||
variables may hold an integer, a float, list, dict, tuple, str, long etc.,
|
||||
among other things. In the viewpoint of Boost.Python and C++, these
|
||||
Pythonic variables are just instances of class <tt>object</tt>. We shall see in
|
||||
this chapter how to deal with Python objects.</p>
|
||||
<p>
|
||||
As mentioned, one of the goals of Boost.Python is to provide a
|
||||
bidirectional mapping between C++ and Python while maintaining the Python
|
||||
feel. Boost.Python C++ <tt>object</tt>s are as close as possible to Python. This
|
||||
should minimize the learning curve significantly.</p>
|
||||
<p>
|
||||
<img src="theme/python.png"></img></p>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="auto_overloading.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="basic_interface.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,88 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Overloading</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="call_policies.html">
|
||||
<link rel="next" href="default_arguments.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Overloading</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="call_policies.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="default_arguments.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
The following illustrates a scheme for manually wrapping an overloaded
|
||||
member functions. Of course, the same technique can be applied to wrapping
|
||||
overloaded non-member functions.</p>
|
||||
<p>
|
||||
We have here our C++ class:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>X
|
||||
</span><span class=special>{
|
||||
</span><span class=keyword>bool </span><span class=identifier>f</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>)
|
||||
{
|
||||
</span><span class=keyword>return </span><span class=keyword>true</span><span class=special>;
|
||||
}
|
||||
|
||||
</span><span class=keyword>bool </span><span class=identifier>f</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>double </span><span class=identifier>b</span><span class=special>)
|
||||
{
|
||||
</span><span class=keyword>return </span><span class=keyword>true</span><span class=special>;
|
||||
}
|
||||
|
||||
</span><span class=keyword>bool </span><span class=identifier>f</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>double </span><span class=identifier>b</span><span class=special>, </span><span class=keyword>char </span><span class=identifier>c</span><span class=special>)
|
||||
{
|
||||
</span><span class=keyword>return </span><span class=keyword>true</span><span class=special>;
|
||||
}
|
||||
|
||||
</span><span class=keyword>int </span><span class=identifier>f</span><span class=special>(</span><span class=keyword>int </span><span class=identifier>a</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>b</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>c</span><span class=special>)
|
||||
{
|
||||
</span><span class=keyword>return </span><span class=identifier>a </span><span class=special>+ </span><span class=identifier>b </span><span class=special>+ </span><span class=identifier>c</span><span class=special>;
|
||||
};
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Class X has 4 overloaded functions. We shall start by introducing some
|
||||
member function pointer variables:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>bool </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx1</span><span class=special>)(</span><span class=keyword>int</span><span class=special>) = &</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
|
||||
</span><span class=keyword>bool </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx2</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>double</span><span class=special>) = &</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
|
||||
</span><span class=keyword>bool </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx3</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>double</span><span class=special>, </span><span class=keyword>char</span><span class=special>)= &</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
|
||||
</span><span class=keyword>int </span><span class=special>(</span><span class=identifier>X</span><span class=special>::*</span><span class=identifier>fx4</span><span class=special>)(</span><span class=keyword>int</span><span class=special>, </span><span class=keyword>int</span><span class=special>, </span><span class=keyword>int</span><span class=special>) = &</span><span class=identifier>X</span><span class=special>::</span><span class=identifier>f</span><span class=special>;
|
||||
</span></pre></code>
|
||||
<p>
|
||||
With these in hand, we can proceed to define and wrap this for Python:</p>
|
||||
<code><pre>
|
||||
<span class=special>.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>fx1</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>fx2</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>fx3</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, </span><span class=identifier>fx4</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="call_policies.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="default_arguments.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,79 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>QuickStart</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="next" href="building_hello_world.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>QuickStart</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><img src="theme/l_arr_disabled.gif" border="0"></td>
|
||||
<td width="20"><a href="building_hello_world.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
The Boost Python Library is a framework for interfacing Python and
|
||||
C++. It allows you to quickly and seamlessly expose C++ classes
|
||||
functions and objects to Python, and vice-versa, using no special
|
||||
tools -- just your C++ compiler. It is designed to wrap C++ interfaces
|
||||
non-intrusively, so that you should not have to change the C++ code at
|
||||
all in order to wrap it, making Boost.Python ideal for exposing
|
||||
3rd-party libraries to Python. The library's use of advanced
|
||||
metaprogramming techniques simplifies its syntax for users, so that
|
||||
wrapping code takes on the look of a kind of declarative interface
|
||||
definition language (IDL).</p>
|
||||
<a name="hello_world"></a><h2>Hello World</h2><p>
|
||||
Following C/C++ tradition, let's start with the "hello, world". A C++
|
||||
Function:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>char </span><span class=keyword>const</span><span class=special>* </span><span class=identifier>greet</span><span class=special>()
|
||||
{
|
||||
</span><span class=keyword>return </span><span class=string>"hello, world"</span><span class=special>;
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
can be exposed to Python by writing a Boost.Python wrapper:</p>
|
||||
<code><pre>
|
||||
<span class=preprocessor>#include </span><span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>python</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>>
|
||||
</span><span class=keyword>using </span><span class=keyword>namespace </span><span class=identifier>boost</span><span class=special>::</span><span class=identifier>python</span><span class=special>;
|
||||
|
||||
</span><span class=identifier>BOOST_PYTHON_MODULE</span><span class=special>(</span><span class=identifier>hello</span><span class=special>)
|
||||
{
|
||||
</span><span class=identifier>def</span><span class=special>(</span><span class=string>"greet"</span><span class=special>, </span><span class=identifier>greet</span><span class=special>);
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
That's it. We're done. We can now build this as a shared library. The
|
||||
resulting DLL is now visible to Python. Here's a sample Python session:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>import </span><span class=identifier>hello
|
||||
</span><span class=special>>>> </span><span class=identifier>print </span><span class=identifier>hello</span><span class=special>.</span><span class=identifier>greet</span><span class=special>()
|
||||
</span><span class=identifier>hello</span><span class=special>, </span><span class=identifier>world
|
||||
</span></pre></code>
|
||||
<blockquote><p><i><b>Next stop... Building your Hello World module from start to finish...</b></i></p></blockquote><table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><img src="theme/l_arr_disabled.gif" border="0"></td>
|
||||
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|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
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</body>
|
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</html>
|
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|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Using the interpreter</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="embedding.html">
|
||||
<link rel="next" href="iterators.html">
|
||||
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|
||||
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|
||||
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|
||||
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|
||||
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|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Using the interpreter</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="embedding.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="iterators.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
As you probably already know, objects in Python are reference-counted.
|
||||
Naturally, the <tt>PyObject</tt>s of the Python/C API are also reference-counted.
|
||||
There is a difference however. While the reference-counting is fully
|
||||
automatic in Python, the Python/C API requires you to do it
|
||||
<a href="http://www.python.org/doc/current/api/refcounts.html">
|
||||
by hand</a>. This is
|
||||
messy and especially hard to get right in the presence of C++ exceptions.
|
||||
Fortunately Boost.Python provides the <a href="../../v2/handle.html">
|
||||
handle</a> class
|
||||
template to automate the process.</p>
|
||||
<a name="reference_counting_handles"></a><h2>Reference-counting handles</h2><p>
|
||||
There are two ways in which a function in the Python/C API can return a
|
||||
<tt>PyObject*</tt>: as a <i>borrowed reference</i> or as a <i>new reference</i>. Which of
|
||||
these a function uses, is listed in that function's documentation. The two
|
||||
require slightely different approaches to reference-counting but both can
|
||||
be 'handled' by Boost.Python.</p>
|
||||
<p>
|
||||
For a function returning a <i>borrowed reference</i> we'll have to tell the
|
||||
<tt>handle</tt> that the <tt>PyObject*</tt> is borrowed with the aptly named
|
||||
<a href="../../v2/handle.html#borrowed-spec">
|
||||
borrowed</a> function. Two functions
|
||||
returning borrowed references are <a href="http://www.python.org/doc/current/api/importing.html#l2h-125">
|
||||
PyImport_AddModule</a> and <a href="http://www.python.org/doc/current/api/moduleObjects.html#l2h-594">
|
||||
PyModule_GetDict</a>.
|
||||
The former returns a reference to an already imported module, the latter
|
||||
retrieves a module's namespace dictionary. Let's use them to retrieve the
|
||||
namespace of the <tt>__main__</tt> module:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>handle</span><span class=special><> </span><span class=identifier>main_module</span><span class=special>(</span><span class=identifier>borrowed</span><span class=special>( </span><span class=identifier>PyImport_AddModule</span><span class=special>(</span><span class=string>"__main__"</span><span class=special>) ));
|
||||
</span><span class=identifier>handle</span><span class=special><> </span><span class=identifier>main_namespace</span><span class=special>(</span><span class=identifier>borrowed</span><span class=special>( </span><span class=identifier>PyModule_GetDict</span><span class=special>(</span><span class=identifier>main_module</span><span class=special>.</span><span class=identifier>get</span><span class=special>()) ));
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Because the Python/C API doesn't know anything about <tt>handle</tt>s, we used
|
||||
the <a href="../../v2/handle.html#handle-spec-observers">
|
||||
get</a> member function to
|
||||
retrieve the <tt>PyObject*</tt> from which the <tt>handle</tt> was constructed.</p>
|
||||
<p>
|
||||
For a function returning a <i>new reference</i> we can just create a <tt>handle</tt>
|
||||
out of the raw <tt>PyObject*</tt> without wrapping it in a call to borrowed. One
|
||||
such function that returns a new reference is <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-55">
|
||||
PyRun_String</a> which we'll
|
||||
discuss in the next section.</p>
|
||||
<table width="80%" border="0" align="center">
|
||||
<tr>
|
||||
<td class="note_box">
|
||||
<img src="theme/lens.gif"></img> <b>Handle is a class <i>template</i>, so why haven't we been using any template parameters?</b><br>
|
||||
<br>
|
||||
<tt>handle</tt> has a single template parameter specifying the type of the managed object. This type is <tt>PyObject</tt> 99% of the time, so the parameter was defaulted to <tt>PyObject</tt> for convenience. Therefore we can use the shorthand <tt>handle<></tt> instead of the longer, but equivalent, <tt>handle<PyObject></tt>.
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<a name="running_python_code"></a><h2>Running Python code</h2><p>
|
||||
To run Python code from C++ there is a family of functions in the API
|
||||
starting with the PyRun prefix. You can find the full list of these
|
||||
functions <a href="http://www.python.org/doc/current/api/veryhigh.html">
|
||||
here</a>. They
|
||||
all work similarly so we will look at only one of them, namely:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>PyObject</span><span class=special>* </span><span class=identifier>PyRun_String</span><span class=special>(</span><span class=keyword>char </span><span class=special>*</span><span class=identifier>str</span><span class=special>, </span><span class=keyword>int </span><span class=identifier>start</span><span class=special>, </span><span class=identifier>PyObject </span><span class=special>*</span><span class=identifier>globals</span><span class=special>, </span><span class=identifier>PyObject </span><span class=special>*</span><span class=identifier>locals</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
<a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-55">
|
||||
PyRun_String</a> takes the code to execute as a null-terminated (C-style)
|
||||
string in its <tt>str</tt> parameter. The function returns a new reference to a
|
||||
Python object. Which object is returned depends on the <tt>start</tt> paramater.</p>
|
||||
<p>
|
||||
The <tt>start</tt> parameter is the start symbol from the Python grammar to use
|
||||
for interpreting the code. The possible values are:</p>
|
||||
<table width="90%" border="0" align="center"> <tr>
|
||||
<td class="table_title" colspan="6">
|
||||
Start symbols </td>
|
||||
</tr>
|
||||
<tr><tr><td class="table_cells"><a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-58">
|
||||
Py_eval_input</a></td><td class="table_cells">for interpreting isolated expressions</td></tr><td class="table_cells"><a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-59">
|
||||
Py_file_input</a></td><td class="table_cells">for interpreting sequences of statements</td></tr><td class="table_cells"><a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-60">
|
||||
Py_single_input</a></td><td class="table_cells">for interpreting a single statement</td></tr></table>
|
||||
<p>
|
||||
When using <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-58">
|
||||
Py_eval_input</a>, the input string must contain a single expression
|
||||
and its result is returned. When using <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-59">
|
||||
Py_file_input</a>, the string can
|
||||
contain an abitrary number of statements and None is returned.
|
||||
<a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-60">
|
||||
Py_single_input</a> works in the same way as <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-59">
|
||||
Py_file_input</a> but only accepts a
|
||||
single statement.</p>
|
||||
<p>
|
||||
Lastly, the <tt>globals</tt> and <tt>locals</tt> parameters are Python dictionaries
|
||||
containing the globals and locals of the context in which to run the code.
|
||||
For most intents and purposes you can use the namespace dictionary of the
|
||||
<tt>__main__</tt> module for both parameters.</p>
|
||||
<p>
|
||||
We have already seen how to get the <tt>__main__</tt> module's namespace so let's
|
||||
run some Python code in it:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>handle</span><span class=special><> </span><span class=identifier>main_module</span><span class=special>(</span><span class=identifier>borrowed</span><span class=special>( </span><span class=identifier>PyImport_AddModule</span><span class=special>(</span><span class=string>"__main__"</span><span class=special>) ));
|
||||
</span><span class=identifier>handle</span><span class=special><> </span><span class=identifier>main_namespace</span><span class=special>(</span><span class=identifier>borrowed</span><span class=special>( </span><span class=identifier>PyModule_GetDict</span><span class=special>(</span><span class=identifier>main_module</span><span class=special>.</span><span class=identifier>get</span><span class=special>()) ));
|
||||
</span><span class=identifier>handle</span><span class=special><>( </span><span class=identifier>PyRun_String</span><span class=special>(</span><span class=string>"hello = file('hello.txt', 'w')\n"
|
||||
</span><span class=string>"hello.write('Hello world!')\n"
|
||||
</span><span class=string>"hello.close()"</span><span class=special>, </span><span class=identifier>Py_file_input</span><span class=special>,
|
||||
</span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>get</span><span class=special>(), </span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>get</span><span class=special>()) );
|
||||
</span></pre></code>
|
||||
<p>
|
||||
This should create a file called 'hello.txt' in the current directory
|
||||
containing a phrase that is well-known in programming circles.</p>
|
||||
<p>
|
||||
<img src="theme/note.gif"></img> <b>Note</b> that we wrap the return value of <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-55">
|
||||
PyRun_String</a> in a
|
||||
(nameless) <tt>handle</tt> even though we are not interested in it. If we didn't
|
||||
do this, the the returned object would be kept alive unnecessarily. Unless
|
||||
you want to be a Dr. Frankenstein, always wrap <tt>PyObject*</tt>s in <tt>handle</tt>s.</p>
|
||||
<a name="beyond_handles"></a><h2>Beyond handles</h2><p>
|
||||
It's nice that <tt>handle</tt> manages the reference counting details for us, but
|
||||
other than that it doesn't do much. Often we'd like to have a more useful
|
||||
class to manipulate Python objects. But we have already seen such a class
|
||||
in the <a href="object_interface.html">
|
||||
previous section</a>: the aptly named <tt>object</tt>
|
||||
class and it's derivatives. What we haven't seen, is that they can be
|
||||
constructed from a <tt>handle</tt>. The following examples should illustrate this
|
||||
fact:</p>
|
||||
<code>
|
||||
<pre>
|
||||
<span class=identifier>handle</span><span class=special><> </span><span class=identifier>main_module</span><span class=special>(</span><span class=identifier>borrowed</span><span class=special>( </span><span class=identifier>PyImport_AddModule</span><span class=special>(</span><span class=string>"__main__"</span><span class=special>) ));
|
||||
</span><span class=identifier>dict </span><span class=identifier>main_namespace</span><span class=special>(</span><span class=identifier>handle</span><span class=special><>(</span><span class=identifier>borrowed</span><span class=special>( </span><span class=identifier>PyModule_GetDict</span><span class=special>(</span><span class=identifier>main_module</span><span class=special>.</span><span class=identifier>get</span><span class=special>()) )));
|
||||
</span><span class=identifier>handle</span><span class=special><>( </span><span class=identifier>PyRun_String</span><span class=special>(</span><span class=string>"result = 5 ** 2"</span><span class=special>, </span><span class=identifier>Py_file_input</span><span class=special>,
|
||||
</span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>(), </span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>()) );
|
||||
</span><span class=keyword>int </span><span class=identifier>five_squared </span><span class=special>= </span><span class=identifier>extract</span><span class=special><</span><span class=keyword>int</span><span class=special>>( </span><span class=identifier>main_namespace</span><span class=special>[</span><span class=string>"result"</span><span class=special>] );
|
||||
</span></pre>
|
||||
</code>
|
||||
<p>
|
||||
Here we create a dictionary object for the <tt>__main__</tt> module's namespace.
|
||||
Then we assign 5 squared to the result variable and read this variable from
|
||||
the dictionary. Another way to achieve the same result is to let
|
||||
<a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-55">
|
||||
PyRun_String</a> return the result directly with <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-58">
|
||||
Py_eval_input</a>:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>object </span><span class=identifier>result</span><span class=special>(</span><span class=identifier>handle</span><span class=special><>( </span><span class=identifier>PyRun_String</span><span class=special>(</span><span class=string>"5 ** 2"</span><span class=special>, </span><span class=identifier>Py_eval_input</span><span class=special>,
|
||||
</span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>(), </span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>()) ));
|
||||
</span><span class=keyword>int </span><span class=identifier>five_squared </span><span class=special>= </span><span class=identifier>extract</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=identifier>result</span><span class=special>);
|
||||
</span></pre></code>
|
||||
<p>
|
||||
<img src="theme/note.gif"></img> <b>Note</b> that <tt>object</tt>'s member function to return the wrapped
|
||||
<tt>PyObject*</tt> is called <tt>ptr</tt> instead of <tt>get</tt>. This makes sense if you
|
||||
take into account the different functions that <tt>object</tt> and <tt>handle</tt>
|
||||
perform.</p>
|
||||
<a name="exception_handling"></a><h2>Exception handling</h2><p>
|
||||
If an exception occurs in the execution of some Python code, the <a href="http://www.python.org/doc/current/api/veryhigh.html#l2h-55">
|
||||
PyRun_String</a> function returns a null pointer. Constructing a <tt>handle</tt> out of this null pointer throws <a href="../../v2/errors.html#error_already_set-spec">
|
||||
error_already_set</a>, so basically, the Python exception is automatically translated into a C++ exception when using <tt>handle</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>try
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>object </span><span class=identifier>result</span><span class=special>(</span><span class=identifier>handle</span><span class=special><>( </span><span class=identifier>PyRun_String</span><span class=special>(</span><span class=string>"5/0"</span><span class=special>, </span><span class=identifier>Py_eval_input</span><span class=special>,
|
||||
</span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>(), </span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>()) ));
|
||||
// </span><span class=identifier>execution </span><span class=identifier>will </span><span class=identifier>never </span><span class=identifier>get </span><span class=identifier>here</span><span class=special>:
|
||||
</span><span class=keyword>int </span><span class=identifier>five_divided_by_zero </span><span class=special>= </span><span class=identifier>extract</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=identifier>result</span><span class=special>);
|
||||
}
|
||||
</span><span class=keyword>catch</span><span class=special>(</span><span class=identifier>error_already_set</span><span class=special>)
|
||||
{
|
||||
// </span><span class=identifier>handle </span><span class=identifier>the </span><span class=identifier>exception </span><span class=identifier>in </span><span class=identifier>some </span><span class=identifier>way
|
||||
</span><span class=special>}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
The <tt>error_already_set</tt> exception class doesn't carry any information in itself. To find out more about the Python exception that occurred, you need to use the <a href="http://www.python.org/doc/api/exceptionHandling.html">
|
||||
exception handling functions</a> of the Python/C API in your catch-statement. This can be as simple as calling <a href="http://www.python.org/doc/api/exceptionHandling.html#l2h-70">
|
||||
PyErr_Print()</a> to print the exception's traceback to the console, or comparing the type of the exception with those of the <a href="http://www.python.org/doc/api/standardExceptions.html">
|
||||
standard exceptions</a>:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>catch</span><span class=special>(</span><span class=identifier>error_already_set</span><span class=special>)
|
||||
{
|
||||
</span><span class=keyword>if </span><span class=special>(</span><span class=identifier>PyErr_ExceptionMatches</span><span class=special>(</span><span class=identifier>PyExc_ZeroDivisionError</span><span class=special>))
|
||||
{
|
||||
// </span><span class=identifier>handle </span><span class=identifier>ZeroDivisionError </span><span class=identifier>specially
|
||||
</span><span class=special>}
|
||||
</span><span class=keyword>else
|
||||
</span><span class=special>{
|
||||
// </span><span class=identifier>print </span><span class=identifier>all </span><span class=identifier>other </span><span class=identifier>errors </span><span class=identifier>to </span><span class=identifier>stderr
|
||||
</span><span class=identifier>PyErr_Print</span><span class=special>();
|
||||
}
|
||||
}
|
||||
</span></pre></code>
|
||||
<p>
|
||||
(To retrieve even more information from the exception you can use some of the other exception handling functions listed <a href="http://www.python.org/doc/api/exceptionHandling.html">
|
||||
here</a>.)</p>
|
||||
<p>
|
||||
If you'd rather not have <tt>handle</tt> throw a C++ exception when it is constructed, you can use the <a href="../../v2/handle.html#allow_null-spec">
|
||||
allow_null</a> function in the same way you'd use borrowed:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>handle</span><span class=special><> </span><span class=identifier>result</span><span class=special>(</span><span class=identifier>allow_null</span><span class=special>( </span><span class=identifier>PyRun_String</span><span class=special>(</span><span class=string>"5/0"</span><span class=special>, </span><span class=identifier>Py_eval_input</span><span class=special>,
|
||||
</span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>(), </span><span class=identifier>main_namespace</span><span class=special>.</span><span class=identifier>ptr</span><span class=special>()) ));
|
||||
</span><span class=keyword>if </span><span class=special>(!</span><span class=identifier>result</span><span class=special>)
|
||||
// </span><span class=identifier>Python </span><span class=identifier>exception </span><span class=identifier>occurred
|
||||
</span><span class=keyword>else
|
||||
</span><span class=comment>// everything went okay, it's safe to use the result
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="embedding.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="iterators.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 Dirk Gerrits<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,122 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
|
||||
<title>Virtual Functions with Default Implementations</title>
|
||||
<link rel="stylesheet" href="theme/style.css" type="text/css">
|
||||
<link rel="prev" href="deriving_a_python_class.html">
|
||||
<link rel="next" href="class_operators_special_functions.html">
|
||||
</head>
|
||||
<body>
|
||||
<table width="100%" height="48" border="0" cellspacing="2">
|
||||
<tr>
|
||||
<td><img src="theme/c%2B%2Bboost.gif">
|
||||
</td>
|
||||
<td width="85%">
|
||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Virtual Functions with Default Implementations</b></font>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="deriving_a_python_class.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_operators_special_functions.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<p>
|
||||
Recall that in the <a href="class_virtual_functions.html">
|
||||
previous section</a>, we
|
||||
wrapped a class with a pure virtual function that we then implemented in
|
||||
C++ or Python classes derived from it. Our base class:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Base
|
||||
</span><span class=special>{
|
||||
</span><span class=keyword>virtual </span><span class=keyword>int </span><span class=identifier>f</span><span class=special>() = </span><span class=number>0</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
had a pure virtual function <tt>f</tt>. If, however, its member function <tt>f</tt> was
|
||||
not declared as pure virtual:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>Base
|
||||
</span><span class=special>{
|
||||
</span><span class=keyword>virtual </span><span class=keyword>int </span><span class=identifier>f</span><span class=special>() { </span><span class=keyword>return </span><span class=number>0</span><span class=special>; }
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
and instead had a default implementation that returns <tt>0</tt>, as shown above,
|
||||
we need to add a forwarding function that calls the <tt>Base</tt> default virtual
|
||||
function <tt>f</tt> implementation:</p>
|
||||
<code><pre>
|
||||
<span class=keyword>struct </span><span class=identifier>BaseWrap </span><span class=special>: </span><span class=identifier>Base
|
||||
</span><span class=special>{
|
||||
</span><span class=identifier>BaseWrap</span><span class=special>(</span><span class=identifier>PyObject</span><span class=special>* </span><span class=identifier>self_</span><span class=special>)
|
||||
: </span><span class=identifier>self</span><span class=special>(</span><span class=identifier>self_</span><span class=special>) {}
|
||||
</span><span class=keyword>int </span><span class=identifier>f</span><span class=special>() { </span><span class=keyword>return </span><span class=identifier>call_method</span><span class=special><</span><span class=keyword>int</span><span class=special>>(</span><span class=identifier>self</span><span class=special>, </span><span class=string>"f"</span><span class=special>); }
|
||||
</span><span class=keyword>int </span><span class=identifier>default_f</span><span class=special>() { </span><span class=keyword>return </span><span class=identifier>Base</span><span class=special>::</span><span class=identifier>f</span><span class=special>(); } // <<=== ***</span><span class=identifier>ADDED</span><span class=special>***
|
||||
</span><span class=identifier>PyObject</span><span class=special>* </span><span class=identifier>self</span><span class=special>;
|
||||
};
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Then, Boost.Python needs to keep track of 1) the dispatch function <tt>f</tt> and
|
||||
2) the forwarding function to its default implementation <tt>default_f</tt>.
|
||||
There's a special <tt>def</tt> function for this purpose. Here's how it is
|
||||
applied to our example above:</p>
|
||||
<code><pre>
|
||||
<span class=identifier>class_</span><span class=special><</span><span class=identifier>Base</span><span class=special>, </span><span class=identifier>BaseWrap</span><span class=special>>(</span><span class=string>"Base"</span><span class=special>)
|
||||
.</span><span class=identifier>def</span><span class=special>(</span><span class=string>"f"</span><span class=special>, &</span><span class=identifier>Base</span><span class=special>::</span><span class=identifier>f</span><span class=special>, &</span><span class=identifier>BaseWrap</span><span class=special>::</span><span class=identifier>default_f</span><span class=special>)
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Note that we are allowing <tt>Base</tt> objects to be instantiated this time,
|
||||
unlike before where we specifically defined the <tt>class_<Base></tt> with
|
||||
<tt>no_init</tt>.</p>
|
||||
<p>
|
||||
In Python, the results would be as expected:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>base </span><span class=special>= </span><span class=identifier>Base</span><span class=special>()
|
||||
>>> </span><span class=keyword>class </span><span class=identifier>Derived</span><span class=special>(</span><span class=identifier>Base</span><span class=special>):
|
||||
... </span><span class=identifier>def </span><span class=identifier>f</span><span class=special>(</span><span class=identifier>self</span><span class=special>):
|
||||
... </span><span class=keyword>return </span><span class=number>42
|
||||
</span><span class=special>...
|
||||
>>> </span><span class=identifier>derived </span><span class=special>= </span><span class=identifier>Derived</span><span class=special>()
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Calling <tt>base.f()</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>base</span><span class=special>.</span><span class=identifier>f</span><span class=special>()
|
||||
</span><span class=number>0
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Calling <tt>derived.f()</tt>:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>derived</span><span class=special>.</span><span class=identifier>f</span><span class=special>()
|
||||
</span><span class=number>42
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Calling <tt>call_f</tt>, passing in a <tt>base</tt> object:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>call_f</span><span class=special>(</span><span class=identifier>base</span><span class=special>)
|
||||
</span><span class=number>0
|
||||
</span></pre></code>
|
||||
<p>
|
||||
Calling <tt>call_f</tt>, passing in a <tt>derived</tt> object:</p>
|
||||
<code><pre>
|
||||
<span class=special>>>> </span><span class=identifier>call_f</span><span class=special>(</span><span class=identifier>derived</span><span class=special>)
|
||||
</span><span class=number>42
|
||||
</span></pre></code>
|
||||
<table border="0">
|
||||
<tr>
|
||||
<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
|
||||
<td width="30"><a href="deriving_a_python_class.html"><img src="theme/l_arr.gif" border="0"></a></td>
|
||||
<td width="20"><a href="class_operators_special_functions.html"><img src="theme/r_arr.gif" border="0"></a></td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,156 +0,0 @@
|
||||
<html>
|
||||
<head>
|
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<title>Boost Python Tutorial</title>
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<link rel="stylesheet" href="doc/theme/style.css" type="text/css">
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<td><img src="doc/theme/c%2B%2Bboost.gif">
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</td>
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<td width="85%">
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||||
<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Boost Python Tutorial</b></font>
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</table>
|
||||
<br>
|
||||
<table width="80%" border="0" align="center">
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||||
<tr>
|
||||
<td class="toc_title">Table of contents</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/quickstart.html">QuickStart</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/building_hello_world.html">Building Hello World</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/exposing_classes.html">Exposing Classes</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/constructors.html">Constructors</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/class_data_members.html">Class Data Members</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/class_properties.html">Class Properties</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/inheritance.html">Inheritance</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/class_virtual_functions.html">Class Virtual Functions</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/deriving_a_python_class.html">Deriving a Python Class</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/virtual_functions_with_default_implementations.html">Virtual Functions with Default Implementations</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/class_operators_special_functions.html">Class Operators/Special Functions</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/functions.html">Functions</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/call_policies.html">Call Policies</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/overloading.html">Overloading</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/default_arguments.html">Default Arguments</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/auto_overloading.html">Auto-Overloading</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/object_interface.html">Object Interface</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/basic_interface.html">Basic Interface</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/derived_object_types.html">Derived Object types</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/extracting_c___objects.html">Extracting C++ objects</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/enums.html">Enums</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/embedding.html">Embedding</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L1">
|
||||
<a href="doc/using_the_interpreter.html">Using the interpreter</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/iterators.html">Iterators</a>
|
||||
</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td class="toc_cells_L0">
|
||||
<a href="doc/exception_translation.html">Exception Translation</a>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<br>
|
||||
<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
|
||||
<font size="2">Permission to copy, use, modify, sell and distribute this document
|
||||
is granted provided this copyright notice appears in all copies. This document
|
||||
is provided "as is" without express or implied warranty, and with
|
||||
no claim as to its suitability for any purpose. </font> </p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,163 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
<title>Boost.Python - April 2002 Progress Report</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">April 2002 Progress Report</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<h2>Contents</h2>
|
||||
<dl class="index">
|
||||
<dt><a href="#accomplishments">Accomplishments</a></dt>
|
||||
<dl class="index">
|
||||
<dt><a href="#arity">Arbitrary Arity Support</a></dt>
|
||||
<dt><a href="#callbacks">New Callback Interface</a></dt>
|
||||
<dt><a href="#policies">Call Policies for Construtors</a></dt>
|
||||
<dt><a href="#bugs">Real Users, Real Bugs</a></dt>
|
||||
<dt><a href="#insights">New Insights</a></dt>
|
||||
<dt><a href="#v1">Boost.Python V1 Maintenance</a></dt>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#missing">What's Missing</a></dt>
|
||||
|
||||
</dl>
|
||||
|
||||
<h2><a name="accomplishments">Accomplishments</a></h2>
|
||||
|
||||
April was a short month as far as Boost.Python was concerned, since
|
||||
the spring ISO C++ Committee Meeting (and associated vacation)
|
||||
occupied me for the 2nd half of the month. However, a suprising amount
|
||||
of work got done...
|
||||
|
||||
<h3><a name="arity">Arbitrary Arity Support</a></h3>
|
||||
|
||||
I began using the <a
|
||||
href="../../../preprocessor/doc/index.htm">Boost.Preprocessor</a>
|
||||
metaprogramming library to generate support for functions and member
|
||||
functions of arbitrary arity, which was, to say the least, quite an
|
||||
adventure. The feedback cycle resulting from my foray into
|
||||
Boost.Preprocessor resulted in several improvements to the library,
|
||||
most notably in its documentation.
|
||||
|
||||
<p>
|
||||
|
||||
Boost.Python now supports calls of up to 17 arguments on most
|
||||
compilers. Because most EDG-based compilers have dismal preprocessor
|
||||
performance, I had to "manually" expand the metaprograms for
|
||||
arities from zero to fifteen arguments, and EDG-based compilers with
|
||||
<code>__EDG_VERSION__ <= 245</code> only support 15
|
||||
arguments by default. If some crazy program finds a need for more than
|
||||
the default arity support, users can increase the base support by
|
||||
setting the <code>BOOST_PYTHON_MAX_ARITY</code> preprocessor symbol.
|
||||
|
||||
<h3><a name="callbacks">New Callback Interface</a></h3>
|
||||
|
||||
I mentioned in <a href="Mar2002.html">last month's report</a> that I
|
||||
wasn't pleased with the interface for the interface for calling into
|
||||
Python, so now it has been redesigned. The new interface is outlined
|
||||
in <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-April/000953.html">this
|
||||
message</a> (though the GCC 2.95.3 bugs have been fixed).
|
||||
|
||||
<h3><a name="policies">Call Policies for Constructors</a></h3>
|
||||
|
||||
On April 2nd, I <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-April/000916.html">announced</a>
|
||||
support for the use of call policies with constructors.
|
||||
|
||||
<h3><a name="bugs">Real Users, Real Bugs</a></h3>
|
||||
|
||||
At least two people outside of Kull began actually using Boost.Python
|
||||
v2 in earnest this month. Peter Bienstman and Pearu Pearson both
|
||||
provided valuable real-world bug reports that helped me to improve the
|
||||
library's robustness.
|
||||
|
||||
<h3><a name="insights">New Insights</a></h3>
|
||||
|
||||
<a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-May/001010.html"
|
||||
>Answering some of Pearu's questions</a> about explicitly converting
|
||||
objects between Python and C++ actually led me to a new understanding
|
||||
of the role of the current conversion facilities. In Boost.Python v1,
|
||||
all conversions between Python and C++ were handled by a single family
|
||||
of functions, called <code>to_python()</code> and
|
||||
<code>from_python()</code>. Since the primary role of Boost.Python is
|
||||
to wrap C++ functions in Python, I used these names for the first kind
|
||||
of converters I needed: those that extract C++ objects to be used as
|
||||
function arguments and which C++ function return values to
|
||||
Python. The better-considered approach in Boost.Python v2 uses a
|
||||
completely different mechanism for conversions used when calling
|
||||
Python from C++, as in wrapped virtual function implementations. I
|
||||
usually think of this as a "callback", as in "calling
|
||||
back into Python", and I named the converters used in callbacks
|
||||
accordingly: <code>to_python_callback</code> and
|
||||
<code>from_python_callback</code>. However, as it turns out, the
|
||||
behavior of the "callback" converters is the appropriate one
|
||||
for users who want to explicitly extract a C++ value from a Python
|
||||
object, or create a Python object from a C++ value. The upshot is that
|
||||
it probably makes sense to change the name of the existing <code>to_python</code> and
|
||||
<code>from_python</code> so those names are available for the
|
||||
user-friendly explicit converters.
|
||||
|
||||
<p>
|
||||
<a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-May/001013.html">Another
|
||||
of Pearu's questions</a> pushes momentum further in the direction of a
|
||||
more-sophisticated overloading mechanism than the current
|
||||
simple-minded "first match" approach, as I suggested <a
|
||||
href="Mar2002.html#implicit_conversions">last month</a>.
|
||||
|
||||
<h3><a name="v1">Boost.Python V1 Maintenance</a></h3>
|
||||
|
||||
As much as I'm looking forward to retiring Boost.Python v1, a
|
||||
significant amount of effort has been being spent dealing with support
|
||||
problems; the saying that code rots when left alone is true, and
|
||||
Boost.Python is no exception. Eventually it became obvious to me that
|
||||
we were going to have to invest some effort in keeping V1 healthy
|
||||
while working on V2. Ralf and I have expanded support for various
|
||||
compilers and stabilized the V1 codebase considerably. We discarded
|
||||
the obsolete Visual Studio projects which were causing so much
|
||||
confusion. Still to do before the next Boost release:
|
||||
<ol>
|
||||
<li>Update the build/test documentation with detailed instructions for
|
||||
configuring various toolsets.
|
||||
<li>Provide some links to Boost.Python v2 to let people know what's
|
||||
coming.
|
||||
</ol>
|
||||
|
||||
|
||||
<h2><a name="missing">What's Missing</a></h2>
|
||||
|
||||
Last month I announced that I would implement the following which are
|
||||
not yet complete:
|
||||
<ol>
|
||||
<li>Document all implemented features
|
||||
<li>Implement conversions for <code>char</code> types. This is
|
||||
implemented but not tested, so we have to assume it doesn't work.
|
||||
</ol>
|
||||
|
||||
These are my first priority for this month (especially the
|
||||
documentation).
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
|
||||
2002. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,153 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href=../../../../boost.css>
|
||||
|
||||
<title>Boost.Python - CallPolicies Concept</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">CallPolicies Concept</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#composition">CallPolicies Composition</a></dt>
|
||||
|
||||
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#CallPolicies-concept">CallPolicies Concept</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>Models of the CallPolicies concept are used to specialize the behavior
|
||||
of Python callable objects generated by Boost.Python to wrapped C++
|
||||
objects like function and member function pointers, providing three
|
||||
behaviors:</p>
|
||||
|
||||
<ol>
|
||||
<li><code>precall</code> - Python argument tuple management before the
|
||||
wrapped object is invoked</li>
|
||||
|
||||
<li><code>result_converter</code> - C++ return value handling</li>
|
||||
|
||||
<li><code>postcall</code> - Python argument tuple and result management
|
||||
after the wrapped object is invoked</li>
|
||||
</ol>
|
||||
|
||||
<h2><a name="composition"></a>CallPolicies Composition</h2>
|
||||
In order to allow the use of multiple models of CallPolicies in the same
|
||||
callable object, Boost.Python's CallPolicies class templates provide a
|
||||
chaining interface which allows them to be recursively composed. This
|
||||
interface takes the form of an optional template parameter,
|
||||
<code>Base</code> which defaults to <a href=
|
||||
"default_call_policies.html#default_call_policies-spec"><code>default_call_policies</code></a>.
|
||||
By convention, the <code>precall</code> function of the <code>Base</code>
|
||||
is invoked <i>after</i> the <code>precall</code> function supplied by the
|
||||
outer template, and the <code>postcall</code> function of the
|
||||
<code>Base</code> is invoked <i>before</i> the <code>postcall</code>
|
||||
function of the outer template. If a <code>result_converter</code> is
|
||||
supplied by the outer template, it <i>replaces</i> any
|
||||
<code>result_converter</code> supplied by the <code>Base</code>. For an
|
||||
example, see <a href=
|
||||
"return_internal_reference.html#return_internal_reference-spec"><code>return_internal_reference</code></a>.
|
||||
|
||||
|
||||
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
|
||||
|
||||
<h3><a name="CallPolicies-concept"></a>CallPolicies Concept</h3>
|
||||
|
||||
<p>In the table below, <code><b>x</b></code> denotes an object whose type
|
||||
<code><b>P</b></code> is a model of CallPolicies, <code><b>a</b></code>
|
||||
denotes a <code>PyObject*</code> pointing to a Python argument tuple
|
||||
object, and <code><b>r</b></code> denotes a <code>PyObject*</code>
|
||||
referring to a "preliminary" result object.</p>
|
||||
|
||||
<table summary="CallPolicies expressions" border="1" cellpadding="5">
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
|
||||
<td><b>Type</b></td>
|
||||
|
||||
<td><b>Result/Semantics</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>x.precall(a)</code></td>
|
||||
|
||||
<td>convertible to <code>bool</code></td>
|
||||
|
||||
<td>returns <code>false</code> and <code><a href=
|
||||
"http://www.python.org/doc/2.2/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a>() != 0</code>
|
||||
upon failure, <code>true</code> otherwise.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>P::result_converter</code></td>
|
||||
|
||||
<td>A model of <a href=
|
||||
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a>.</td>
|
||||
|
||||
<td>An MPL unary <a href=
|
||||
"../../../mpl/doc/paper/html/usage.html#metafunctions.classes">Metafunction
|
||||
Class</a> used produce the "preliminary" result object.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>x.postcall(a, r)</code></td>
|
||||
|
||||
<td>convertible to <code>PyObject*</code></td>
|
||||
|
||||
<td>0 <code>0</code> and <code><a href=
|
||||
"http://www.python.org/doc/2.2/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a>() != 0</code>
|
||||
upon failure. Must "conserve references" even in the event of an
|
||||
exception. In other words, if <code>r</code> is not returned, its
|
||||
reference count must be decremented; if another existing object is
|
||||
returned, its reference count must be incremented.</td>
|
||||
</tr>
|
||||
</table>
|
||||
Models of CallPolicies are required to be <a href=
|
||||
"../../../utility/CopyConstructible.html">CopyConstructible</a>.
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
|
||||
<p>Permission to copy, use, modify, sell and distribute this software is
|
||||
granted provided this copyright notice appears in all copies. This
|
||||
software is provided "as is" without express or implied warranty, and
|
||||
with no claim as to its suitability for any purpose.</p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,81 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href=../../../../boost.css>
|
||||
<title>Boost.Python - Dereferenceable Concept</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">Dereferenceable Concept</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#Dereferenceable-concept">Dereferenceable Concept</a></dt>
|
||||
</dl>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>Instances of a dereferenceable type can be used like a pointer to access an lvalue.
|
||||
|
||||
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
|
||||
<h3><a name="Dereferenceable-concept"></a>Dereferenceable Concept</h3>
|
||||
|
||||
<p>In the table below, <code><b>x</b></code> denotes an object whose
|
||||
type is a model of Dereferenceable.
|
||||
|
||||
<table summary="Dereferenceable expressions" border="1" cellpadding="5">
|
||||
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
<td><b>Requirements</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>*x</code></td>
|
||||
<td>An lvalue
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
If <code><b>x</b></code> is not a pointer type, it also must satsify the following expression:
|
||||
|
||||
<table summary="Dereferenceable expressions" border="1" cellpadding="5">
|
||||
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
<td><b>Operational Semantics</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>x.get()</code></td>
|
||||
<td><code>&*x</code>, or a null pointer
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<hr>
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
29 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002. All Rights Reserved.</i>
|
||||
|
||||
<p>Permission to copy, use, modify, sell
|
||||
and distribute this software is granted provided this copyright notice appears
|
||||
in all copies. This software is provided "as is" without express or implied
|
||||
warranty, and with no claim as to its suitability for any purpose.
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,93 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href=../../../../boost.css>
|
||||
<title>Boost.Python - Extractor Concept</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">Extractor Concept</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#Extractor-concept">Extractor Concept</a></dt>
|
||||
</dl>
|
||||
<dt><a href="#notes">Notes</a></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>An Extractor is a class which Boost.Python can use to extract C++
|
||||
objects from Python objects, and is typically used by facilities that
|
||||
define <code>from_python</code> conversions for
|
||||
"traditional" Python extension types.
|
||||
|
||||
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
|
||||
<h3><a name="Extractor-concept"></a>Extractor Concept</h3>
|
||||
|
||||
<p>In the table below, <code><b>X</b></code> denotes a model of
|
||||
Extractor and <code><b>a</b></code> denotes an instance of a Python
|
||||
object type.
|
||||
|
||||
<table summary="Extractor expressions" border="1" cellpadding="5">
|
||||
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
<td><b>Type</b></td>
|
||||
<td><b>Semantics</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>X::execute(a)</code></td>
|
||||
<td>non-void
|
||||
<td>Returns the C++ object being extracted. The
|
||||
<code>execute</code> function must not be overloaded.
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>&a.ob_type</code>
|
||||
<td><code><a
|
||||
href="http://www.python.org/doc/2.2/ext/dnt-type-methods.html">PyTypeObject</a>**</code>
|
||||
<td>Points to the <code>ob_type</code> field of an object which is
|
||||
layout-compatible with <code>PyObject</code>
|
||||
</tr>
|
||||
|
||||
</tr>
|
||||
|
||||
</table>
|
||||
|
||||
<h2><a name="notes"></a>Notes</h2>
|
||||
|
||||
Informally, an Extractor's <code>execute</code> member must be a
|
||||
non-overloaded static function whose single argument is a Python
|
||||
object type. Acceptable Python object types include those publicly (and
|
||||
unambiguously) derived from <code>PyObject</code>, and POD types which
|
||||
are layout-compatible with PyObject.
|
||||
|
||||
<hr>
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002. All Rights Reserved.</i>
|
||||
|
||||
<p>Permission to copy, use, modify, sell
|
||||
and distribute this software is granted provided this copyright notice appears
|
||||
in all copies. This software is provided "as is" without express or implied
|
||||
warranty, and with no claim as to its suitability for any purpose.
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,71 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href=../../../../boost.css>
|
||||
<title>Boost.Python - Holder Concept</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">HolderGenerator Concept</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#HolderGenerator-concept">HolderGenerator Concept</a></dt>
|
||||
</dl>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>A HolderGenerator is a unary metafunction class which returns types
|
||||
suitable for holding instances of its argument in a wrapped C++ class
|
||||
instance.
|
||||
|
||||
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
|
||||
<h3><a name="HolderGenerator-concept"></a>HolderGenerator Concept</h3>
|
||||
|
||||
<p>In the table below, <code><b>G</b></code> denotes an type which
|
||||
models HolderGenerator, and <code><b>X</b></code> denotes a class
|
||||
type.
|
||||
|
||||
<table summary="Holder expressions" border="1" cellpadding="5">
|
||||
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
<td><b>Requirements</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>G::apply<X>::type</code></td>
|
||||
<td>A concrete subclass of <a
|
||||
href="instance_holder.html#instance_holder-spec">instance_holder</a>
|
||||
which can hold objects of type <code>X</code>.
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<hr>
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002. All Rights Reserved.</i>
|
||||
|
||||
<p>Permission to copy, use, modify, sell
|
||||
and distribute this software is granted provided this copyright notice appears
|
||||
in all copies. This software is provided "as is" without express or implied
|
||||
warranty, and with no claim as to its suitability for any purpose.
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,226 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
<title>Boost.Python - June 2002 Progress Report</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">June 2002 Progress Report</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<h2>Contents</h2>
|
||||
<dl class="index">
|
||||
<dt><a href="#intro">Introduction</a></dt>
|
||||
<dt><a href="#handle"><code>handle<T></code></a></dt>
|
||||
<dt><a href="#object"><code>object</code></a></dt>
|
||||
<dl class="index">
|
||||
<dt><a href="#operators"><code>object</code> operators</a></dt>
|
||||
<dt><a href="#conversions"><code>object</code> conversions</a></dt>
|
||||
</dl>
|
||||
<dt><a href="#list"><code>list</code></a></dt>
|
||||
<dt><a href="#numerics"><code>Numerics</code></a></dt>
|
||||
<dt><a href="#community">Community</a></dt>
|
||||
<dt><a href="#next">What's Next</a></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="intro">Introduction</a></h2>
|
||||
|
||||
July was mostly focused on allowing expressive manipulation of
|
||||
individual Python objects, or what Ralf Grosse-Kunstleve calls
|
||||
"Writing Python in C++". The work began with this <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001311.html">posting</a>,
|
||||
which outlines the issues and intention.
|
||||
|
||||
<h2><a name="handle"><code>handle<T></code></a></h2>
|
||||
|
||||
The most basic element needed was a replacement for the
|
||||
<code>reference<></code> class template and the
|
||||
<code>ref</code> typedef from Boost.Python v1, a simple smart
|
||||
pointer to a Python object. The old v1 typedef
|
||||
"<code>ref</code>" (for
|
||||
<code>reference<PyObject></code>) had to be retired because I
|
||||
thought it would be too confusing given the importance of <code><a
|
||||
href="../../../bind/ref.html">boost::ref</a>()</code> to this
|
||||
library. I began a <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001311.html">discussion</a>of
|
||||
possible names, and it was eventually <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001337.html">decided</a>
|
||||
to rename <code>reference</code> to <code>handle</code> and supply a
|
||||
default argument so that <code>ref</code> could be spelled
|
||||
<code>handle<></code> without an additional typedef. There
|
||||
were also some interface changes to make it safer and more-efficient
|
||||
to interface with the raw
|
||||
<code>PyObject*</code>s forced on us by Python's 'C' API. A
|
||||
discussion of those protocols can be found <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001401.html">here</a>.
|
||||
|
||||
<h2><a name="handle"><code>object</code></a></h2>
|
||||
|
||||
It is intended that users will seldom need or want to work with
|
||||
<code>handle<></code>; its major distinguishing features are
|
||||
that it gives direct access to the underlying object representation
|
||||
through <code>operator*</code> and <code>operator-></code>, and
|
||||
that can be <code>NULL</code>, both sources of danger. Instead the
|
||||
library provides a class called <code>object</code>, which
|
||||
encapsulates a valid Python object and provides a similar interface to
|
||||
Python's.
|
||||
|
||||
<h3><a name="operators"><code>object</code> operators</a></h3>
|
||||
|
||||
The first challenge was to provide support for object manipulations
|
||||
using a Python-like syntax, mostly in the form of operator overloads:
|
||||
|
||||
<table border="1">
|
||||
<tr><th>Python <th>C++
|
||||
|
||||
<tr>
|
||||
<td><code>y = x.foo</code> <td><code>y = x.attr("foo");
|
||||
<tr>
|
||||
<td><code>x.foo = 1</code> <td><code>x.attr("foo") = 1;
|
||||
|
||||
<tr>
|
||||
<td><code>y = x[z]</code> <td><code>y = x[z];
|
||||
<tr>
|
||||
<td><code>x[z] = 1</code> <td><code>x[z] = 1;
|
||||
|
||||
<tr>
|
||||
<td><code>y = x[3:-1]</code> <td><code>y = x.slice(3,-1);
|
||||
|
||||
<tr>
|
||||
<td><code>y = x[3:]</code> <td><code>y = x.slice(3,_);
|
||||
|
||||
<tr>
|
||||
<td><code>y = x[:-2]</code> <td><code>y = x.slice(_,-2);
|
||||
|
||||
<tr>
|
||||
<td><code>z = x(1, y)</code> <td><code>z = x(1, y);
|
||||
<tr>
|
||||
<td><code>z = x.f(1, y)</code> <td><code>z = x.attr("f")(1, y);
|
||||
|
||||
<tr>
|
||||
<td><code>not x</code> <td><code>!x
|
||||
|
||||
<tr>
|
||||
<td><code>x and y</code> <td><code>x and y
|
||||
</table>
|
||||
|
||||
I'm still a unsatisfied with the interface for attribute access. There
|
||||
original proposal used a syntax like this one:
|
||||
<pre>
|
||||
y = x._("foo");
|
||||
x._("foo") = 1;
|
||||
</pre>
|
||||
|
||||
which was only marginally better than what we've got. Niki Spahiev
|
||||
then <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001447.html">pointed
|
||||
out</a> a potential conflict with the macro which GNU Gettext <a
|
||||
href="http://www.gnu.org/manual/gettext/html_mono/gettext.html#SEC6">suggests</a>
|
||||
people define. This unfortunate state of affairs forced us into using
|
||||
<code>attr</code> instead. I'd still like to find a better interface,
|
||||
but the lack of overloadable C++ operators which aren't already used
|
||||
in Python is an obstacle. The comma operator is still a possibility,
|
||||
but it has the wrong precedence:
|
||||
<pre>
|
||||
y = x,"foo" // error
|
||||
x,"foo" = 1; // error
|
||||
|
||||
y = (x,"foo"); // ok
|
||||
(x,"foo") = 1; // ok
|
||||
</pre>
|
||||
|
||||
Well, I guess we could consider adding that to the interface without
|
||||
removing <code>attr()</code>, to see how it plays out...
|
||||
|
||||
<h3><a name="operators"><code>object</code> conversions</a></h3>
|
||||
|
||||
The <code>object</code> class also provided an opportunity to replace
|
||||
Boost.Python v1's <code>to_python()</code> as a user-level
|
||||
interface. Instead, <code>object</code> has a templated constructor
|
||||
which can be used to convert any C++ object to Python using the same
|
||||
underlying mechanisms used for the arguments to <code><a
|
||||
href="call.html">call</a><></code>.
|
||||
|
||||
<p>Incidentally, the implementation of operator and conversion support
|
||||
for object uncovered an inordinate number of compiler bugs in our
|
||||
targeted platforms. It was a lot more "interesting" than it
|
||||
should have been.
|
||||
|
||||
<h2><a name="list"><code>list</code></a></h2>
|
||||
|
||||
With <code>object</code> implemented, it was time to begin replacing
|
||||
the ad-hoc implementations of <code>list</code>, <code>string</code>,
|
||||
and <code>dictionary</code> supplied by Boost.Python v1 with something
|
||||
more robust. I started with <code>list</code> as an example. Because
|
||||
<code>object</code> already provides all of the requisite operators,
|
||||
publicly deriving <code>list</code> from object seemed like a good
|
||||
choice. The remaining issues were what do do about the one-argument
|
||||
list constructor (which in Python attempts to convert its argument to
|
||||
a list), and how to deal converting with <code>list</code> arguments
|
||||
to wrapped functions. Some of the issues are laid out in <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001551.html">this
|
||||
thread</a>. Ultimately, it was decided that <code>list(x)</code>
|
||||
should do the same thing in C++ as in Python (conversion), while
|
||||
<code>list</code> arguments should only match Python
|
||||
<code>list</code>s (and <code>list</code> subclasses). The
|
||||
implementation worked well, and provided a <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001586.html">roadmap</a>
|
||||
for the protocol to be used for implementation of the other built-in
|
||||
types.
|
||||
|
||||
<h2><a name="numerics">Numerics</a></h2>
|
||||
|
||||
Support for C++ <code>long long</code> and <code>unsigned long
|
||||
long</code>
|
||||
(and <code>__int64</code> on MSVC) to/from python conversions was
|
||||
added this month. We also improved handling of numeric overflows when
|
||||
converting, e.g., a Python int to a type with a more limited range of
|
||||
representation.
|
||||
|
||||
<h2><a name="community">Community</a></h2>
|
||||
|
||||
<ul>
|
||||
<li>Ralf W. Grosse-Kunstleve and Nick Sauter have implemented
|
||||
<a href="http://cci.lbl.gov/boost/">multiplatform nightly
|
||||
build-and-test</a> runs for Boost.Python V2 at LBL.
|
||||
|
||||
<li>Dave Hawkes has made significant progress on generating the
|
||||
Python <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-June/001503.html">built-in
|
||||
function and API wrappers</a>
|
||||
|
||||
<li>Achim Domma has agreed to take up the job of implementing the
|
||||
<code>str</code>, <code>dict</code>, and <code>tuple</code> classes.
|
||||
</ul>
|
||||
|
||||
Deep thanks to all the Boost.Python contributors! This project
|
||||
wouldn't be possible without your participation.
|
||||
|
||||
<h2><a name="next">What's Next</a></h2>
|
||||
|
||||
As I write this we are already well into the month of July, so I
|
||||
suggest you consult the <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-July/">Mailing
|
||||
List Archive</a> if you want to know what's been happening. Otherwise
|
||||
you'll just have to wait till next month (hopefully the beginning).
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
|
||||
2002. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,234 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
<title>Boost.Python - March 2002 Progress Report</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">March 2002 Progress Report</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<h2>Contents</h2>
|
||||
<dl class="index">
|
||||
<dt><a href="#accomplishments">Accomplishments</a></dt>
|
||||
<dl class="index">
|
||||
<dt><a href="#calling_python">Calling Python from C++</a></dt>
|
||||
<dt><a href="#virtual_functions">Virtual Functions</a></dt>
|
||||
<dt><a href="#abstract_classes">Abstract Classes</a></dt>
|
||||
<dt><a href="#implicit_conversions">C++ Implicit Conversions</a></dt>
|
||||
<dt><a href="#data_members">C++ Data Members</a></dt>
|
||||
<dt><a href="#miscellaneous">Miscellaneous</a></dt>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#future">The Near future</a></dt>
|
||||
|
||||
<dt><a href="#notes">Notes</a></dt>
|
||||
|
||||
</dl>
|
||||
|
||||
<h2><a name="accomplishments">Accomplishments</a></h2>
|
||||
|
||||
March was mostly devoted to the reimplementation of features from
|
||||
Boost.Python v1, and some new features. Re-examination of the features
|
||||
from Boost.Python v1 allowed me to make significant improvements.
|
||||
|
||||
<h3><a name="calling_python">Calling Python from C++</a></h3>
|
||||
|
||||
The ability to call Python from C++ is crucial for virtual function
|
||||
support. Implementing this feature well for V2 proved to be more
|
||||
interesting than I expected. You can review most of the relevant
|
||||
design decisions
|
||||
<a href="callbacks.txt">here</a>.
|
||||
|
||||
<p>
|
||||
One point which <i>isn't</i> emphasized in that document is that there
|
||||
are subtle differences in the way <code>from_python</code> conversions
|
||||
work when used for C++ function arguments and Python function return
|
||||
values. In particular, while <code>T const&</code> arguments may
|
||||
invoke rvalue converters, a reference-to-const return value requires
|
||||
an lvalue converter, since a temporary conversion result would leave
|
||||
the returned reference dangling.
|
||||
|
||||
<p>I'm not particularly pleased with the current callback interface,
|
||||
since it usually results in constructs like:
|
||||
<pre>
|
||||
<u>return returning</u><X&>::call(f, obj);
|
||||
</pre>
|
||||
However, I think the following may be possible and I plan to investigate:
|
||||
<pre>
|
||||
return apply<X&>(f, obj);
|
||||
</pre>
|
||||
I'm open to suggestion for better names (and syntaxes)!
|
||||
|
||||
<h3><a name="virtual_functions">Virtual Functions</a></h3>
|
||||
|
||||
Once Python callbacks were implemented, it was just a short step to
|
||||
implementing virtual functions. Python extension class exposing a C++
|
||||
class whose virtual functions are overridable in Python must actually
|
||||
hold a C++ instance of a class <i>derived</i> from the one exposed to
|
||||
Python. Needing some way for users to specify that class, I added an
|
||||
optional template argument to <code>value_holder_generator</code> and
|
||||
<code>pointer_holder_generator<></code> to specify the class
|
||||
actually held. This move began to put pressure on the
|
||||
<code>class_<></code> interface, since the need for the user to
|
||||
produce complicated instantations of
|
||||
<code>class_<></code> was increased:
|
||||
|
||||
<pre>
|
||||
class<Foo, bases<>, value_holder_generator<Foo_callback> >("Foo")
|
||||
.def("hello", &Foo::hello)
|
||||
...
|
||||
</pre>
|
||||
|
||||
<h3><a name="abstract_classes">Abstract Classes</a></h3>
|
||||
|
||||
Normally when a C++ class is exposed to Python, the library registers
|
||||
a conversion function which allows users to wrap functions returning
|
||||
values of that type. Naturally, these return values are temporaries,
|
||||
so the conversion function must make a copy in some
|
||||
dynamically-allocated storage (a "holder") which is managed
|
||||
by the corresponding Python object.
|
||||
|
||||
<p>Unfortunately, in the case of abstract classes (and other types
|
||||
without a publicly-accessible copy constructor), instantiating this
|
||||
conversion function causes a compilation error. In order to support
|
||||
non-copyable classes, there had to be some way to prevent the library
|
||||
from trying to instantiate the conversion function. The only practical
|
||||
approach I could think of was to add an additional template parameter
|
||||
to the <code>class_<></code> interface. When the number of
|
||||
template parameters with useful defaults begins to grow, it is often
|
||||
hard to choose an order which allows users to take advantage of the
|
||||
defaults.
|
||||
|
||||
<p>
|
||||
|
||||
This was the straw that broke the
|
||||
<code>class_<></code> interface's back and caused the redesign
|
||||
whose outcome is detailed <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-March/000892.html">here</a>.
|
||||
The approach allows the user to supply the optional parameters in an
|
||||
arbitrary order. It was inspired by the use of <a
|
||||
href="../../../utility/iterator_adaptors.htm#named_tempalte_parameters">named
|
||||
template parameters</a> in the <a
|
||||
href="../../../utility/iterator_adaptors.htm">Boost Iterator Adaptor
|
||||
Library</a>, though in this case it is possible to deduce the meaning
|
||||
of the template parameters entirely from their type properties,
|
||||
resulting in a simpler interface. Although the move from a
|
||||
policy-based design to what resembles a configuration DSL usually
|
||||
implies a loss of flexibility, in this case I think any costs are far
|
||||
outweighed by the advantages.
|
||||
|
||||
<p>Note: working around the limitations of the various compilers I'm
|
||||
supporting was non-trivial, and resulted in a few messy implementation
|
||||
details. It might be a good idea to switch to a more-straightforward
|
||||
approach once Metrowerks CodeWarrior Pro8 is released.
|
||||
|
||||
<h3><a name="implicit_conversions">C++ Implicit Conversions</a></h3>
|
||||
|
||||
Support for C++ implicit conversion involves creating
|
||||
<code>from_python</code> converters for a type <code>U</code> which in
|
||||
turn use <code>from_python</code> converters registered for a type
|
||||
<code>T</code> where there exists a implicit conversion from
|
||||
<code>T</code> to <code>U</code>. The current implementation is
|
||||
subject to two inefficiencies:
|
||||
<ol>
|
||||
|
||||
<li>Because an rvalue <code>from_python</code> converter produces two
|
||||
pieces of data (a function and a <code>void*</code>) from its
|
||||
<code>convertible()</code> function, we end up calling the function
|
||||
for <code>T</code> twice: once when the converter is looked up in the
|
||||
registry, and again when the conversion is actually performed.
|
||||
|
||||
<li>A vector is used to mark the "visited" converters, preventing
|
||||
infinite recursion as <code>T</code> to
|
||||
<code>U</code> and <code>U</code> to <code>T</code> converters
|
||||
continually search through one-another.
|
||||
|
||||
</ol>
|
||||
|
||||
I consider the former to be a minor issue. The second may or may not
|
||||
prove to be computationally significant, but I believe that
|
||||
architecturally, it points toward a need for more sophisticated
|
||||
overload resolution. It may be that we want CLOS-style multimethod
|
||||
dispatching along with C++ style rules that prevent more than one
|
||||
implicit conversion per argument.
|
||||
|
||||
<h3><a name="data_members">C++ Data Members</a></h3>
|
||||
|
||||
To supply the ability to directly access data members, I was able to
|
||||
hijack the new Python <a
|
||||
href="http://www.python.org/2.2/descrintro.html#property">property</a>
|
||||
type. I had hoped that I would also be able to re-use the work of <a
|
||||
href="make_function.html">make_function</a> to create callable python
|
||||
objects from C++ functions which access a data member of a given
|
||||
class. C++ facilities for specifying data member pointer non-type
|
||||
template arguments require the user to explicitly specify the type of
|
||||
the data member and this under-utilized feature is also not
|
||||
well-implemented on all compilers, so passing the member pointer as a
|
||||
runtime value is the only practical approach. The upshot is that any
|
||||
such entity would actually have to be a function <i>object</i>, and I
|
||||
haven't implemented automatic wrapping of C++ callable function
|
||||
objects yet, so there is less re-use in the implementation than I'd
|
||||
like. I hope to implement callable object wrapping and refactor this
|
||||
code one day. I also hope to implement static data member support,
|
||||
for which Python's property will not be an appropriate descriptor.
|
||||
|
||||
<h3><a name="miscellaneous">Miscellaneous</a></h3>
|
||||
<ul>
|
||||
<li>Moved <code>args<></code> and <code>bases<></code> from unnamed namespace to <code>boost::python</code> in their own header files.
|
||||
<li>Convert <code>NULL</code> pointers returned from wrapped C++ functions to <code>None</code>.
|
||||
<li>Improved some compile-time error checks.
|
||||
<li>Eliminated <code>boost/python/detail/eval.hpp</code> in favor of
|
||||
more-general <code>boost/mpl/apply.hpp</code>.
|
||||
<li>General code cleanup and refactoring.
|
||||
<li>Works with Microsoft Visual C++ 7.0
|
||||
<li>Warning suppression for many compilers
|
||||
<li>Elegant interface design for exporting <code>enum</code> types.
|
||||
</ul>
|
||||
<hr>
|
||||
|
||||
<h2><a name="future">The Near Future</a></h2>
|
||||
|
||||
Before April 15th I plan to
|
||||
<ol>
|
||||
<li>Document all implemented features
|
||||
<li>Implement a <code>CallPolicy</code> interface for constructors of wrapped
|
||||
classes
|
||||
<li>Implement conversions for <code>char</code> types.
|
||||
<li>Implement automated code generation for all headers containing
|
||||
families of overloaded functions to handle arbitrary arity.
|
||||
</ol>
|
||||
|
||||
I also hope to implement a mechanism for generating conversions
|
||||
between arbitrary Python sequences and C++ containers, if time permits
|
||||
(and others haven't already done it)!
|
||||
|
||||
<h2><a name="notes">Notes</a></h2>
|
||||
|
||||
The older version of KCC used by Kull is generating lots of warnings
|
||||
about a construct I use to instantiate static members of various class
|
||||
templates. I'm thinking of moving to an idiom which uses a function
|
||||
template to suppress it, but worry about bloating the size of debug
|
||||
builds. Since KCC users may be moving to GCC, I'm not sure that it's
|
||||
worth doing anything about it.
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
|
||||
2002. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,309 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
<title>Boost.Python - May 2002 Progress Report</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">May 2002 Progress Report</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<h2>Contents</h2>
|
||||
<dl class="index">
|
||||
<dt><a href="#intro">Introduction</a></dt>
|
||||
<dt><a href="#features">New Features</a></dt>
|
||||
<dl>
|
||||
<dt><a href="#aix_shared">Shared Library Support for AIX</a><dd>
|
||||
<dt><a href="#class_enhancements">Class Enhancements</a><dd>
|
||||
<dl>
|
||||
<dt><a href="#operators">Operators</a><dd>
|
||||
<dt><a href="#iterators">Iterators</a><dd>
|
||||
<dt><a href="#properties">Properties</a><dd>
|
||||
<dt><a href="#setattr">setattr</a><dd>
|
||||
<dt><a href="#module">__module__ Attribute</a><dd>
|
||||
</dl>
|
||||
<dt><a href="#back_reference">back_reference</a><dd>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#documentation">Documentation</a></dt>
|
||||
<dt><a href="#misc">Miscellaneous</a></dt>
|
||||
<dl class="index">
|
||||
<dt><a href="#converters">Converters</a></dt>
|
||||
<dt><a href="#checkins">Checkins Mailing List</a></dt>
|
||||
<dt><a href="#shared">Shared Libraries</a></dt>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#next">What's Next</a></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="intro">Introduction</a></h2>
|
||||
|
||||
Aside from library development, work on Boost.Python in May was
|
||||
focused on reducing the support burden. In recent weeks, responding to
|
||||
requests for support, espcially surrounding building the library, had
|
||||
begun to impede progress on development. There was a major push to
|
||||
release a stable 1.28.0 of Boost, including documentation of <a
|
||||
href="../../../../tools/build/index.html">Boost.Build</a> and specific
|
||||
<a href="../building.html">instructions</a> for building Boost.Python
|
||||
v1. The documentation for Boost.Python v2 was also updated as
|
||||
described <a href="#documentation">here</a>.
|
||||
|
||||
<h2><a name="features">New Features</a></h2>
|
||||
|
||||
<h3><a name="aix_shared">Shared Library Support for AIX</a></h3>
|
||||
|
||||
The Kull group required the ability to build and test Boost.Python
|
||||
extensions on AIX, a platform with "creatively designed"
|
||||
shared library semantics. Making this work was a multi-pronged
|
||||
effort, involving changes to Boost.Build and some great research by
|
||||
Martin Casado which uncovered the key mechanism required to allow
|
||||
shared libraries to use functions from the Python executable. The
|
||||
current solution used in Boost.Build relies on a <a
|
||||
href="../../../../tools/build/gen_aix_import_file.py">Python
|
||||
Script</a> as part of the build process. This is not a problem for
|
||||
Boost.Python, as Python will be available. However, the commands
|
||||
issued by the script are so simple that a 100%-pure-Boost.Jam
|
||||
solution is surely possible. Linking on AIX is sufficiently
|
||||
interesting to have skewed the Boost.Python development schedule a
|
||||
bit.
|
||||
|
||||
<h3><a name="class_enhancements">Class Enhancements</a></h3>
|
||||
|
||||
<h4><a name="operators">Operators</a></h4>
|
||||
|
||||
Support for exposing C++ operators and functions as the corresponding
|
||||
Python special methods was added. Thinking that the Boost.Python
|
||||
<a href="../special.html#numeric">v1 interface</a> was a little too
|
||||
esoteric (especially the use of
|
||||
<code>left_operand<...>/right_operand<...></code> for
|
||||
asymmetric operands), I introduced a simple form of <a
|
||||
href="http://osl.iu.edu/~tveldhui/papers/Expression-Templates/exprtmpl.html">expression
|
||||
templates</a> which allow users to simply write the expressions that
|
||||
should be wrapped, as in this <a href="operators.html#examples">example</a>.
|
||||
|
||||
<h4><a name="iterators">Iterators</a></h4>
|
||||
|
||||
Python iterator support as required by the Kull project resulted in a
|
||||
highly flexible interface allowing:
|
||||
|
||||
<dl>
|
||||
|
||||
<dt>Direct exposure of a class' <code>begin()</code> and
|
||||
<code>end()</code> functions:
|
||||
|
||||
<pre>
|
||||
...
|
||||
.def("__iter__", iterator<list_int>())
|
||||
</pre>
|
||||
<dd>
|
||||
|
||||
<dt>Creation of iterators from member functions...
|
||||
<pre>
|
||||
...
|
||||
.def("__iter__"
|
||||
, range(&my_class::x_begin, &my_class::x_end))
|
||||
)
|
||||
</pre>
|
||||
<dd>
|
||||
|
||||
<dt>...and member data:
|
||||
<pre>
|
||||
...
|
||||
.def("__iter__"
|
||||
, range(&std::pair<char*,char*>::first, &std::pair<char*,char*>::second))
|
||||
)
|
||||
</pre>
|
||||
<dd>
|
||||
|
||||
<dt>The ability to specify <a
|
||||
href="CallPolicies.html">CallPolicies</a>, e.g. to prevent copying of
|
||||
heavyweight values:
|
||||
|
||||
<pre>
|
||||
...
|
||||
.def("__iter__",
|
||||
, range<return_value_policy<copy_non_const_reference> >(
|
||||
&my_sequence<heavy>::begin
|
||||
, &my_sequence<heavy>::end))
|
||||
</pre>
|
||||
<dd>
|
||||
|
||||
</dl>
|
||||
|
||||
<h4><a name="properties">Properties</a></h4>
|
||||
|
||||
The Kull iteration interfaces also required the ability to iterate
|
||||
over a sequence specified by an instance's attribute:
|
||||
<pre>
|
||||
>>> f = field()
|
||||
>>> for e in f.elements:
|
||||
... print e,
|
||||
</pre>
|
||||
|
||||
This forced the exposure of the <a
|
||||
href="http://www.python.org/2.2/descrintro.html#property"><code>property</code></a>
|
||||
interface used internally to implement the data member exposure
|
||||
facility described in <a
|
||||
href="Mar2002#data_members">March</a>. Properties are an
|
||||
incredibly useful idiom, so it's good to be able to provide them
|
||||
at little new development cost.
|
||||
|
||||
<h4><a name="setattr">setattr</a></h4>
|
||||
|
||||
<code>class_<></code> acquired a <code>setattr</code> member
|
||||
function which allows users to easily add new Python objects as class
|
||||
attributes.
|
||||
|
||||
<h4><a name="module">__module__ Attribute</a></h4>
|
||||
|
||||
Ralf Grosse-Kunstleve has been working on pickling support for v2. To
|
||||
make it work correctly, he had to make sure that a class'
|
||||
<code>__module__</code> attribute was set correctly.
|
||||
|
||||
<h3><a name="back_reference"><code>back_reference</code></a></h3>
|
||||
|
||||
The new <code>back_reference<T></code> template can be used as a
|
||||
function parameter when the user needs access to both a <code>T</code>
|
||||
argument and to the Python object which manages it. The function will
|
||||
only match in the overload resolution process if it would match the
|
||||
same function signature with <code>T</code> substituted for
|
||||
<code>back_reference<T></code>. This feature is not yet
|
||||
documented.
|
||||
|
||||
<h2><a name="documentation">Documentation</a></h2>
|
||||
|
||||
In a major effort to prepare Boost.Python v2 to replace v1, many pages
|
||||
of new reference documentation were added:
|
||||
|
||||
<blockquote>
|
||||
|
||||
<dl>
|
||||
<dt><a href="CallPolicies.html">CallPolicies.html</a><dd>
|
||||
<dt><a href="Dereferenceable.html">Dereferenceable.html</a><dd>
|
||||
<dt><a href="Extractor.html">Extractor.html</a><dd>
|
||||
<dt><a href="HolderGenerator.html">HolderGenerator.html</a><dd>
|
||||
<dt><a href="ResultConverter.html">ResultConverter.html</a><dd>
|
||||
<dt><a href="call_method.html">call_method.html</a><dd>
|
||||
<dt><a href="callbacks.html">callbacks.html</a><dd>
|
||||
<dt><a href="data_members.html">data_members.html</a><dd>
|
||||
<dt><a href="has_back_reference.html">has_back_reference.html</a><dd>
|
||||
<dt><a href="implicit.html">implicit.html</a><dd>
|
||||
<dt><a href="instance_holder.html">instance_holder.html</a><dd>
|
||||
<dt><a href="operators.html">operators.html</a><dd>
|
||||
<dt><a href="ptr.html">ptr.html</a><dd>
|
||||
<dt><a href="type_id.html">type_id.html</a><dd>
|
||||
<dt><a href="with_custodian_and_ward.html">with_custodian_and_ward.html</a><dd>
|
||||
</dl>
|
||||
|
||||
</blockquote>
|
||||
Major updates were made to the following pages:
|
||||
|
||||
|
||||
<blockquote>
|
||||
<dl>
|
||||
<dt><a href="call.html">call.html</a><dd> <dt><a href="updated">updated</a><dd>
|
||||
<dt><a href="class.html">class.html</a><dd>
|
||||
<dt><a href="reference.html">reference.html</a><dd>
|
||||
</dl>
|
||||
</blockquote>
|
||||
|
||||
As usual, careful documentation forces one to consider the
|
||||
interface again, and there were many interface changes
|
||||
associated with this effort, including the elevation of the
|
||||
following components from implementation detail to
|
||||
first-class library citizen:
|
||||
|
||||
<blockquote>
|
||||
<dl>
|
||||
<dt>type_id.hpp<dd>
|
||||
<dt>pointee.hpp<dd>
|
||||
<dt>lvalue_from_pytype.hpp<dd></dl>
|
||||
</dl>
|
||||
</blockquote>
|
||||
|
||||
<h2><a name="misc">Miscellaneous</a></h2>
|
||||
|
||||
<h3><a name="converters">Converters</a></h3>
|
||||
|
||||
It appears that the world of C++ <==> Python conversion rules is
|
||||
an endlessly-rich area of exploration. Completing the conversions for
|
||||
<code>char</code> and <code>char const*</code> types, as described at
|
||||
the end of <a href="Apr2002.html#missing">April's report</a>,
|
||||
uncovered some interesting new shades to the problem. It turns out to
|
||||
be worth distinguishing mutable and immutable lvalue conversions,
|
||||
because despite the fact that Python doesn't understand
|
||||
<code>const</code>, it does understand immutability (c.f. Python
|
||||
strings, which expose an immutable <code>char</code> pointer). It is
|
||||
also worth recognizing types which represent lvalue <i>sequences</i>,
|
||||
to prevent Python <code>"foobar"</code> from being silently
|
||||
truncated to C++ <code>'f'</code>. More details on this insight can be
|
||||
found in the mailing list <a
|
||||
href="http://mail.python.org/pipermail/c++-sig/2002-May/001023.html">
|
||||
archive</a>. I don't plan to do anything about this immediately, but I
|
||||
do think it's the right direction to go in the long run.
|
||||
|
||||
<h3><a name="checkins">Checkins Mailing List</a></h3>
|
||||
|
||||
In order to better coordinate changes made by multiple developers, I
|
||||
enabled <a
|
||||
href="http://sourceforge.net/docman/display_doc.php?docid=772&group_id=1">syncmail</a>
|
||||
for the Boost.Python CVS trees, and established an associated <a
|
||||
href="http://lists.sourceforge.net/lists/listinfo/boost-python-cvs">mailing
|
||||
list</a>. Subscribe to this list to receive notices of each new
|
||||
checkin.
|
||||
|
||||
<h3><a name="shared">Shared Libraries</a></h3>
|
||||
|
||||
Beyond the vagaries of dynamic linking on AIX, I have been
|
||||
participating in a more-general discussion of dynamic linking for
|
||||
C++. Needless to say, C++ dynamic linking is of critical importance to
|
||||
Boost.Python: all extension modules are normally built as shared
|
||||
libraries, and Boost.Python extension modules share a common library
|
||||
as well.
|
||||
|
||||
In fact, there are at least two separate conversations. One
|
||||
in the C++ standard extensions mailing list concerns what can be
|
||||
standardized for C++ and shared libraries; the other, mostly on the <a
|
||||
href="http://gcc.gnu.org/ml/gcc/">gcc</a> mailing list, concerns the
|
||||
behavior of GCC on Posix/ELF platforms.
|
||||
|
||||
Some of the GCC threads are here:
|
||||
|
||||
<blockquote>
|
||||
<a
|
||||
href="http://gcc.gnu.org/ml/gcc/2002-05/msg02002.html">http://gcc.gnu.org/ml/gcc/2002-05/msg02002.html</a><br>
|
||||
<a
|
||||
href="http://gcc.gnu.org/ml/gcc/2002-05/msg02945.html">http://gcc.gnu.org/ml/gcc/2002-05/msg02945.html</a><br>
|
||||
<a href="http://gcc.gnu.org/ml/gcc/2002-05/msg01758.html">http://gcc.gnu.org/ml/gcc/2002-05/msg01758.html</a>
|
||||
</blockquote>
|
||||
|
||||
<h2><a name="next">What's Next</a></h2>
|
||||
|
||||
Development is focused on what's needed to be able to retire
|
||||
Boost.Python v1. At the moment, that means deciding the user-friendly
|
||||
interfaces for to_/from_python conversion, and formally exposing the
|
||||
Python object smart pointers and object wrapper classes. Quite a few
|
||||
questions have also been showing up recently about how to embed Python
|
||||
with Boost.Python, and how to link with it statically; the solutions
|
||||
to these issues will probably have to be formalized before long.
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
|
||||
2002. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,156 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - ObjectWrapper Concept</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">ObjectWrapper and TypeWrapper Concepts</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#ObjectWrapper-concept">ObjectWrapper Concept</a></dt>
|
||||
|
||||
<dt><a href="#TypeWrapper-concept">TypeWrapper Concept</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#caveat">Caveat</a></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>This page defines two concepts used to describe classes which manage a
|
||||
Python objects, and which are intended to support usage with a
|
||||
Python-like syntax.</p>
|
||||
|
||||
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
|
||||
|
||||
<h3><a name="ObjectWrapper-concept"></a>ObjectWrapper Concept</h3>
|
||||
Models of the ObjectWrapper concept have <a href=
|
||||
"object.html#object-spec">object</a> as a publicly-accessible base class,
|
||||
and are used to supply special construction behavior and/or additional
|
||||
convenient functionality through (often templated) member functions.
|
||||
Except when the return type <code>R</code> is itself an <a href=
|
||||
"#TypeWrapper-concept">TypeWrapper</a>, a member function invocation of
|
||||
the form
|
||||
<pre>
|
||||
x.<i>some_function</i>(<i>a<small>1</small>, a<small>2</small>,...a<small>n</small></i>)
|
||||
</pre>
|
||||
always has semantics equivalent to:
|
||||
<pre>
|
||||
<a href=
|
||||
"extract.html#extract-spec">extract</a><R>(x.attr("<i>some_function</i>")(<a
|
||||
href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>1</small></i>), <a
|
||||
href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>2</small></i>),...<a
|
||||
href="object.html#object-spec-ctors">object</a>(<i>a<small>n</small></i>)))()
|
||||
</pre>
|
||||
When the <code>R</code> is an <a href=
|
||||
"#TypeWrapper-concept">TypeWrapper</a>, the result type may be
|
||||
constructed by taking direct posession of:
|
||||
<pre>
|
||||
x.attr("<i>some_function</i>")(<a href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>1</small></i>), <a
|
||||
href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>2</small></i>),...<a
|
||||
href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>n</small></i>)).ptr()
|
||||
</pre>
|
||||
[see <a href="#caveat">caveat</a> below]
|
||||
|
||||
<h3><a name="TypeWrapper-concept"></a>TypeWrapper Concept</h3>
|
||||
TypeWrapper is a refinement of ObjectWrapper which is associated with a
|
||||
particular Python type <code>X</code>. For a given TypeWrapper
|
||||
<code>T</code>, a valid constructor expression
|
||||
<pre>
|
||||
T(<i>a<small>1</small>, a<small>2</small>,...a<small>n</small></i>)
|
||||
</pre>
|
||||
builds a new <code>T</code> object managing the result of invoking
|
||||
<code>X</code> with arguments corresponding to
|
||||
<pre>
|
||||
<a href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>1</small></i>), <a
|
||||
href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>2</small></i>),...<a
|
||||
href=
|
||||
"object.html#object-spec-ctors">object</a>(<i>a<small>n</small></i>)
|
||||
</pre>
|
||||
|
||||
When used as arguments to wrapped C++ functions, or as the template
|
||||
parameter to <code><a
|
||||
href="extract.html#extract-spec">extract</a><></code>, only
|
||||
instances of the associated Python type will be considered a match.
|
||||
|
||||
<h3><a name="caveat">Caveat</a></h3>
|
||||
The upshot of the special member function invocation rules when the
|
||||
return type is a TypeWrapper is that it is possible for the returned
|
||||
object to manage a Python object of an inappropriate type. This is not
|
||||
usually a serious problem; the worst-case result is that errors will be
|
||||
detected at runtime a little later than they might otherwise be. For an
|
||||
example of how this can occur, note that the <code><a href=
|
||||
"dict.html#dict-spec">dict</a></code> member function <code>items</code>
|
||||
returns an object of type <code><a href=
|
||||
"list.html#list-spec">list</a></code>. Now suppose the user defines this
|
||||
<code>dict</code> subclass in Python:
|
||||
<pre>
|
||||
>>> class mydict(dict):
|
||||
... def items(self):
|
||||
... return tuple(dict.items(self)) # return a tuple
|
||||
</pre>
|
||||
Since an instance of <code>mydict</code> is also an instance of
|
||||
<code>dict</code>, when used as an argument to a wrapped C++ function,
|
||||
<code><a href="dict.html#dict-spec">boost::python::dict</a></code> can
|
||||
accept objects of Python type <code>mydict</code>. Invoking
|
||||
<code>items()</code> on this object can result in an instance of <code><a
|
||||
href="list.html#list-spec">boost::python::list</a></code> which actually
|
||||
holds a Python tuple. Subsequent attempts to use list methods (e.g.
|
||||
<code>append</code>, or any other mutating operation) on this object will
|
||||
raise the same exception that would occur if you tried to do it from
|
||||
Python.
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
|
||||
<p>Permission to copy, use, modify, sell and distribute this software is
|
||||
granted provided this copyright notice appears in all copies. This
|
||||
software is provided "as is" without express or implied warranty, and
|
||||
with no claim as to its suitability for any purpose.</p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,110 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href=../../../../boost.css>
|
||||
<title>Boost.Python - ResultConverter Concept</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">ResultConverter Concept</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
<dt><a href="#concept-requirements">Concept Requirements</a></dt>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#ResultConverter-concept">ResultConverter Concept</a></dt>
|
||||
<dt><a href="#ResultConverterGenerator-concept">ResultConverterGenerator Concept</a></dt>
|
||||
</dl>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>A ResultConverter for a type <code>T</code> is a type whose
|
||||
instances can be used to convert C++ return values of type
|
||||
<code>T</code> <code>to_python</code>. A ResultConverterGenerator is
|
||||
an MPL unary metafunction class which, given the return type of a C++
|
||||
function, returns a ResultConverter for that type. ResultConverters in
|
||||
Boost.Python generally inspect library's registry of converters to
|
||||
find a suitable converter, but converters which don't use the registry
|
||||
are also possible.
|
||||
|
||||
<h2><a name="concept-requirements"></a>Concept Requirements</h2>
|
||||
<h3><a name="ResultConverter-concept"></a>ResultConverter Concept</h3>
|
||||
|
||||
<p>In the table below, <code><b>C</b></code> denotes a ResultConverter
|
||||
type for a type <b><code>R</code></b> , <code><b>c</b></code> denotes
|
||||
an object of type <code><b>C</b></code> , and <code><b>r</b></code>
|
||||
denotes an object of type <code><b>R</b></code>.
|
||||
|
||||
<table summary="ResultConverter expressions" border="1" cellpadding="5">
|
||||
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
<td><b>Type</b></td>
|
||||
<td><b>Semantics</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>C c;</code></td>
|
||||
<td>
|
||||
<td>Constructs a <code>C</code> object.
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>c.convertible()</code></td>
|
||||
<td>convertible to <code>bool</code></td>
|
||||
<td><code>false</code> iff no conversion from any <code>R</code> value
|
||||
to a Python object is possible.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>c(r)</code></td>
|
||||
<td>convertible to <code>PyObject*</code></td>
|
||||
<td>A pointer to a Python object corresponding to <code>r</code>,
|
||||
or <code>0</code> iff <code>r</code> could not be converted
|
||||
<code>to_python</code>, in which case <a
|
||||
href="http://www.python.org/doc/current/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a>
|
||||
should return non-zero.</td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h3><a name="ResultConverterGenerator-concept"></a>ResultConverterGenerator Concept</h3>
|
||||
<p>In the table below, <code><b>G</b></code> denotes a
|
||||
ResultConverterGenerator type and <code><b>R</b></code> denotes a possible
|
||||
C++ function return type.
|
||||
|
||||
<table summary="ResultConverterGenerator expressions" border="1" cellpadding="5">
|
||||
<tr>
|
||||
<td><b>Expression</b></td>
|
||||
<td><b>Requirements</b></td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td valign="top"><code>G::apply<R>::type</code></td>
|
||||
<td>A ResultConverter type for <code>R</code>.</td>
|
||||
</table>
|
||||
|
||||
<hr>
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
09 May, 2002 <!--Luann's birthday! -->
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002. All Rights Reserved.</i>
|
||||
|
||||
<p>Permission to copy, use, modify, sell
|
||||
and distribute this software is granted provided this copyright notice appears
|
||||
in all copies. This software is provided "as is" without express or implied
|
||||
warranty, and with no claim as to its suitability for any purpose.
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,133 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - Acknowledgments</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Acknowledgments</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<p><a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a> is
|
||||
the architect, designer, and implementor of <b>Boost.Python</b>.</p>
|
||||
|
||||
<p><a href="mailto:brett.calcott@paradise.net.nz">Brett Calcott</a>
|
||||
contributed and maintains the Visual Studio project files and
|
||||
documentation.</p>
|
||||
|
||||
<p><a href="mailto:Gottfried.Ganssauge-at-haufe.de">Gottfried
|
||||
Ganßauge</a> supplied support for opaque pointer conversions,
|
||||
complete with documentation and a regression test (and I didn't
|
||||
even have to ask him for those)!
|
||||
|
||||
<p>Joel de Guzman implemented the <a href="overloads.html">default
|
||||
argument support</a> and wrote the excellent <a href=
|
||||
"../tutorial/index.html">tutorial documentation</a>.</p>
|
||||
|
||||
<p><a href="../../../../people/ralf_w_grosse_kunstleve.htm">Ralf W.
|
||||
Grosse-Kunstleve</a> implemented the <a href="pickle.html">pickle
|
||||
support</a>, and has enthusiastically supported the library since its
|
||||
birth, contributing to design decisions and providing invaluable
|
||||
real-world insight into user requirements. Ralf has written some <a href=
|
||||
"faq.html#question2">extensions</a> for converting C++ containers that I
|
||||
hope will be incorporated into the library soon. He also implemented the
|
||||
cross-module support in the first version of Boost.Python. More
|
||||
importantly, Ralf makes sure nobody forgets the near-perfect synergy of
|
||||
C++ and Python for solving the problems of large-scale software
|
||||
construction.</p>
|
||||
|
||||
<p><a href="../../../../people/aleksey_gurtovoy.htm">Aleksey Gurtovoy</a>
|
||||
wrote an incredible C++ <a href="http://www.mywikinet.com/mpl">Template
|
||||
Metaprogramming Library</a> which allows Boost.Python to perform much of
|
||||
its compile-time magic. In addition, Aleksey very generously contributed
|
||||
his time and deep knowledge of the quirks of various buggy compilers to
|
||||
help us get around problems at crucial moments.</p>
|
||||
|
||||
<p><a href="../../../../people/paul_mensonides.htm">Paul Mensonides</a>,
|
||||
building on the work <a href="../../../../people/vesa_karvonen.htm">Vesa
|
||||
Karvonen</a>, wrote a similarly amazing <a href=
|
||||
"../../../preprocessor/doc/index.html">Preprocessor Metaprogramming
|
||||
Library</a>, and generously contributed the time and expertise to get it
|
||||
working in the Boost.Python library, rewriting much of Boost.Python to
|
||||
use the new preproccessor metaprogramming constructs and helping us to
|
||||
work around buggy and slow C++ preprocessors.</p>
|
||||
|
||||
<p><a href="nicodemus-at-globalite.com.br">Bruno da Silva de
|
||||
Oliveira</a> contributed the ingenious <a
|
||||
href="../../pyste/index.html">Pyste</a> ("Pie-Steh")
|
||||
code generator.
|
||||
|
||||
<p><a href="mailto:nickm@sitius.com">Nikolay Mladenov</a> contributed
|
||||
<code>staticmethod</code> support.</p>
|
||||
|
||||
<p>Martin Casado solved some sticky problems which allow us to build the
|
||||
Boost.Python shared library for AIX's crazy dynamic linking model.</p>
|
||||
|
||||
<p><a href="mailto:achim@procoders.net">Achim Domma</a> contributed some
|
||||
of the <a href="reference.html#object_wrappers">Object Wrappers</a> and
|
||||
HTML templates for this documentation. Dave Hawkes contributed
|
||||
inspiration for the use of the <code><a href=
|
||||
"scope.html#scope-spec">scope</a></code> class to simplify module
|
||||
definition syntax. Pearu Pearson wrote some of the test cases that are in
|
||||
the current test suite.</p>
|
||||
|
||||
<p>The development of this version of Boost.Python was funded in part by
|
||||
the <a href="http://www.llnl.gov/">Lawrence Livermore National
|
||||
Laboratories</a> and by the <a href="http://cci.lbl.gov/">Computational
|
||||
Crystallography Initiative</a> at Lawrence Berkeley National
|
||||
Laboratories.</p>
|
||||
|
||||
<p><a href="http://kogs-www.informatik.uni-hamburg.de/~koethe/">Ullrich
|
||||
Koethe</a> had independently developed a similar system. When he
|
||||
discovered Boost.Python v1, he generously contributed countless hours of
|
||||
coding and much insight into improving it. He is responsible for an early
|
||||
version of the support for function overloading and wrote the support for
|
||||
reflecting C++ inheritance relationships. He has helped to improve
|
||||
error-reporting from both Python and C++ (we hope to do as well in v2
|
||||
again soon), and has designed the original support for exposing numeric
|
||||
operators, including a way to avoid explicit coercion by means of
|
||||
overloading.</p>
|
||||
|
||||
<p>The members of the boost mailing list and the Python community
|
||||
supplied invaluable early feedback. In particular, Ron Clarke, Mark
|
||||
Evans, Anton Gluck, Chuck Ingold, Prabhu Ramachandran, and Barry Scott
|
||||
took the brave step of trying to use Boost.Python while it was still in
|
||||
early stages of development.</p>
|
||||
|
||||
<p>The first version of Boost.Python would not have been possible without
|
||||
the support of Dragon Systems, which supported its development and
|
||||
release as a Boost library.</p>
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
26 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
197
doc/v2/args.html
197
doc/v2/args.html
@@ -1,197 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/args.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/args.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#keyword-expression"><i>keyword-expressions</i></a></dt>
|
||||
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#arg-spec">class <code>arg</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#arg-synopsis">class <code>arg</code>
|
||||
synopsis</a></dt>
|
||||
|
||||
<dt><a href="#arg-ctor">class <code>arg</code>
|
||||
constructor</a></dt>
|
||||
|
||||
<dt><a href="#arg-operator">class <code>arg</code> template
|
||||
<code>operator =</code></a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#keyword-expression-operators"><i>Keyword-expression</i>
|
||||
operator <code>,</code></a></dt>
|
||||
|
||||
<dt><a href="#functions">Functions (deprecated)</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><code><a href=
|
||||
"#args-spec">args</a>(</code>...<code>)</code></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>Supplies a family of overloaded functions for specifying argument
|
||||
keywords for wrapped C++ functions.</p>
|
||||
|
||||
<h2><a name="keyword-expression"></a><i>keyword-expressions</i></h2>
|
||||
|
||||
<p>A <b>keyword-expression</b> results in an object which holds a
|
||||
sequence of <a href="definitions.html#ntbs">ntbs</a>es, and whose type
|
||||
encodes the number of keywords specified. The <b>keyword-expression</b>
|
||||
may contain default values for some or all of the keywords it holds</p>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="arg-spec"></a><code>class arg;</code></h3>
|
||||
|
||||
<p>The objects of class arg are keyword-expressions holding one keyword (
|
||||
size one )</p>
|
||||
|
||||
<h4><a name="arg-synopsis"></a>Class <code>arg</code> synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
struct arg
|
||||
{
|
||||
template <class T>
|
||||
arg &perator = (T const &value);
|
||||
explicit arg (char const *name){elements[0].name = name;}
|
||||
};
|
||||
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="arg-ctor"></a>Class <code>arg</code> constructor</h4>
|
||||
<pre>
|
||||
arg(char const* name);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> The argument must be a <a href=
|
||||
"definitions.html#ntbs">ntbs</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Constructs an <code>arg</code> object holding a
|
||||
keyword with name <code>name</code>.</dt>
|
||||
</dl>
|
||||
|
||||
<h4><a name="arg-operator"></a>Class <code>arg</code> operator =</h4>
|
||||
<pre>
|
||||
template <class T> arg &operator = (T const &value);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> The argument must convertible to python.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Assigns default value for the keyword.</dt>
|
||||
|
||||
<dt><b>Returns:</b> Reference to <code>this</code>.</dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="keyword-expression-operators"><i>Keyword-expression</i>
|
||||
operator <code>,</code></a></h2>
|
||||
<pre>
|
||||
<i>keyword-expression</i> operator , (<i>keyword-expression</i>, const arg &kw) const
|
||||
<i>keyword-expression</i> operator , (<i>keyword-expression</i>, const char *name) const;
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> The argument <code>name</code> must be a <a href=
|
||||
"definitions.html#ntbs">ntbs</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Extends the <i>keyword-expression</i> argument with
|
||||
one more keyword.</dt>
|
||||
|
||||
<dt><b>Returns:</b> The extended <i>keyword-expression</i>.</dt>
|
||||
</dl>
|
||||
|
||||
<h2><font color="#7F7F7F"><a name="functions"></a>Functions
|
||||
(deprecated)</font></h2>
|
||||
|
||||
<h3><a name="args-spec"></a><code><font color=
|
||||
"#7F7F7F">args</font>(</code>...<code>)</code></h3>
|
||||
<pre>
|
||||
<font color="#7F7F7F"> <i>unspecified1</i> args(char const*);
|
||||
<i>unspecified2</i> args(char const*, char const*);
|
||||
.
|
||||
.
|
||||
.
|
||||
<i>unspecifiedN</i> args(char const*, char const*, ... char const*);
|
||||
</font>
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><font color="#7F7F7F"><b>Requires:</b> Every argument must be a <a
|
||||
href="definitions.html#ntbs">ntbs</a>.</font></dt>
|
||||
|
||||
<dt><font color="#7F7F7F"><b>Returns:</b> an object representing a <a
|
||||
href="#keyword-expression"><i>keyword-expression</i></a> encapsulating
|
||||
the arguments passed.</font></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
<pre>
|
||||
#include <boost/python/def.hpp>
|
||||
using namespace boost::python;
|
||||
|
||||
int f(double x, double y, double z=0.0, double w=1.0);
|
||||
|
||||
BOOST_PYTHON_MODULE(xxx)
|
||||
{
|
||||
def("f", f
|
||||
, ( arg("x"), "y", arg("z")=0.0, arg("w")=1.0 )
|
||||
);
|
||||
}
|
||||
</pre>
|
||||
|
||||
<p>Revised 01 August, 2003</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002-2003. All
|
||||
Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,32 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
<title>Boost.Python - Bibliography</title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">Bibliography</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
{{bibliographical information}}
|
||||
<hr>
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
|
||||
2002. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,82 +0,0 @@
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
<title>Boost.Python - <call.hpp></title>
|
||||
</head>
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
<h2 align="center">Header <call.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
<h2>Contents</h2>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
<dt><a href="#functions">Functions</a></dt>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#call-spec">call</a></dt>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
|
||||
</dl>
|
||||
<hr>
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
<p>
|
||||
<code><boost/python/call.hpp></code> defines the <a
|
||||
href="#call-spec"><code>call</code></a> family of overloaded function
|
||||
templates, used to invoke Python callable objects from C++.
|
||||
|
||||
<h2><a name="functions"></a>Functions</h2>
|
||||
<pre>
|
||||
<a name="call-spec">template <class R, class A1, class A2, ... class A<i>n</i>></a>
|
||||
R call(PyObject* callable, A1 const&, A2 const&, ... A<i>n</i> const&)
|
||||
</pre>
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>R</code> is a pointer type, reference
|
||||
type, or a complete type with an accessible copy constructor</dt>
|
||||
|
||||
<dt><b>Effects:</b> Invokes <code>callable(a1, a2, ...a<i>n</i>)</code> in
|
||||
Python, where <code>a1</code>...<code>a<i>n</i></code> are the arguments to
|
||||
<code>call()</code>, converted to Python objects.
|
||||
<dt><b>Returns:</b> The result of the Python call, converted to the C++ type <code>R</code>.</dt>
|
||||
|
||||
</dt>
|
||||
<dt><b>Rationale:</b> For a complete semantic description and
|
||||
rationale, see <a href="callbacks.html">this page</a>.
|
||||
</dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example(s)</h2>
|
||||
|
||||
The following C++ function applies a Python callable object to its two
|
||||
arguments and returns the result. If a Python exception is raised or
|
||||
the result can't be converted to a <code>double</code>, an exception
|
||||
is thrown.
|
||||
|
||||
<pre>
|
||||
double apply2(PyObject* func, double x, double y)
|
||||
{
|
||||
return boost::python::call<double>(func, x, y);
|
||||
}
|
||||
</pre>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
9 May, 2002 <!-- Luann's birthday! -->
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave Abrahams</a>
|
||||
2002. All Rights Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
@@ -1,159 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <call_method.hpp></title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <call_method.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#functions">Functions</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#call_method-spec">call_method</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><code><boost/python/call_method.hpp></code> defines the <a href=
|
||||
"#call_method-spec"><code>call_method</code></a> family of overloaded
|
||||
function templates, used to invoke callable attributes of Python objects
|
||||
from C++.</p>
|
||||
|
||||
<h2><a name="functions"></a>Functions</h2>
|
||||
<pre>
|
||||
<a name=
|
||||
"call_method-spec">template <class R, class A1, class A2, ... class A<i>n</i>></a>
|
||||
R call_method(PyObject* self, char const* method, A1 const&, A2 const&, ... A<i>n</i> const&)
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>R</code> is a pointer type, reference type,
|
||||
or a complete type with an accessible copy constructor</dt>
|
||||
|
||||
<dt><b>Effects:</b> Invokes
|
||||
<code>self.<i>method</i>(a1, a2, ...a<i>n</i>)</code> in
|
||||
Python, where <code>a1</code>...<code>a<i>n</i></code> are the
|
||||
arguments to <code>call_method()</code>, converted to Python objects.
|
||||
For a complete semantic description, see <a href="callbacks.html">this
|
||||
page</a>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> The result of the Python call, converted to the C++
|
||||
type <code>R</code>.</dt>
|
||||
|
||||
<dt><b>Rationale:</b> <code>call_method</code> is critical to
|
||||
implementing C++ virtual functions which are overridable in Python, as
|
||||
shown by the example below.</dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example(s)</h2>
|
||||
The following C++ illustrates the use of <code>call_method</code> in
|
||||
wrapping a class with a virtual function that can be overridden in
|
||||
Python:
|
||||
|
||||
<h3>C++ Module Definition</h3>
|
||||
<pre>
|
||||
#include <boost/python/module.hpp>
|
||||
#include <boost/python/class.hpp>
|
||||
#include <boost/utility.hpp>
|
||||
#include <cstring>
|
||||
|
||||
// class to be wrapped
|
||||
class Base
|
||||
{
|
||||
public:
|
||||
virtual char const* class_name() const { return "Base"; }
|
||||
virtual ~Base();
|
||||
};
|
||||
|
||||
bool is_base(Base* b)
|
||||
{
|
||||
return !std::strcmp(b->class_name(), "Base");
|
||||
}
|
||||
|
||||
// Wrapper code begins here
|
||||
using namespace boost::python;
|
||||
|
||||
// Callback class
|
||||
class Base_callback : public Base
|
||||
{
|
||||
public:
|
||||
Base_callback(PyObject* self) : m_self(self) {}
|
||||
|
||||
char const* class_name() const { return <b>call_method</b><char const*>(m_self, "class_name"); }
|
||||
char const* Base_name() const { return Base::class_name(); }
|
||||
private:
|
||||
PyObject* const m_self;
|
||||
};
|
||||
|
||||
using namespace boost::python;
|
||||
BOOST_PYTHON_MODULE(my_module)
|
||||
{
|
||||
def("is_base", is_base);
|
||||
|
||||
class_<Base,Base_callback, noncopyable>("Base")
|
||||
.def("class_name", &Base_callback::Base_name)
|
||||
;
|
||||
|
||||
}
|
||||
</pre>
|
||||
|
||||
<h3>Python Code</h3>
|
||||
<pre>
|
||||
>>> from my_module import *
|
||||
>>> class Derived(Base):
|
||||
... def __init__(self):
|
||||
... Base.__init__(self)
|
||||
... def class_name(self):
|
||||
... return self.__class__.__name__
|
||||
...
|
||||
>>> is_base(Base()) # calls the class_name() method from C++
|
||||
1
|
||||
>>> is_base(Derived())
|
||||
0
|
||||
</pre>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,252 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - Calling Python Functions and Methods</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Calling Python Functions and Methods</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#argument_handling">Argument Handling</a></dt>
|
||||
|
||||
<dt><a href="#result_handling">Result Handling</a></dt>
|
||||
|
||||
<dt><a href="#result_handling">Rationale</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction">Introduction</a></h2>
|
||||
The simplest way to call a Python function from C++, given an <code><a
|
||||
href="object.html#object-spec">object</a></code> instance <code>f</code>
|
||||
holding the function, is simply to invoke its function call operator.
|
||||
<pre>
|
||||
f("tea", 4, 2) // In Python: f('tea', 4, 2)
|
||||
</pre>
|
||||
And of course, a method of an <code><a href=
|
||||
"object.html#object-spec">object</a></code> instance <code>x</code> can
|
||||
be invoked by using the function-call operator of the corresponding
|
||||
attribute:
|
||||
<pre>
|
||||
x.attr("tea")(4, 2); // In Python: x.tea(4, 2)
|
||||
</pre>
|
||||
|
||||
<p>If you don't have an <code>object</code> instance, Boost.Python
|
||||
provides two families of function templates, <code><a href=
|
||||
"call.html#call-spec">call</a></code> and <code><a href=
|
||||
"call_method.html#call_method-spec">call_method</a></code>, for invoking
|
||||
Python functions and methods respectively on <code>PyObject*</code>s. The
|
||||
interface for calling a Python function object (or any Python callable
|
||||
object) looks like:</p>
|
||||
<pre>
|
||||
call<ResultType>(callable_object, a1, a2... a<i>N</i>);
|
||||
</pre>
|
||||
Calling a method of a Python object is similarly easy:
|
||||
<pre>
|
||||
call_method<ResultType>(self_object, "<i>method-name</i>", a1, a2... a<i>N</i>);
|
||||
</pre>
|
||||
This comparitively low-level interface is the one you'll use when
|
||||
implementing C++ virtual functions that can be overridden in Python.
|
||||
|
||||
<h2><a name="argument_handling">Argument Handling</a></h2>
|
||||
|
||||
<p>Arguments are converted to Python according to their type. By default,
|
||||
the arguments <code>a1</code>...<code>a<i>N</i></code> are copied into
|
||||
new Python objects, but this behavior can be overridden by the use of
|
||||
<code><a href="ptr.html#ptr-spec">ptr()</a></code> and <a href=
|
||||
"../../../bind/ref.html#reference_wrapper">ref()</a>:</p>
|
||||
<pre>
|
||||
class X : boost::noncopyable
|
||||
{
|
||||
...
|
||||
};
|
||||
|
||||
void apply(PyObject* callable, X& x)
|
||||
{
|
||||
// Invoke callable, passing a Python object which holds a reference to x
|
||||
boost::python::call<void>(callable, boost::ref(x));
|
||||
}
|
||||
</pre>
|
||||
In the table below, <code><b>x</b></code> denotes the actual argument
|
||||
object and <code><b>cv</b></code> denotes an optional
|
||||
<i>cv-qualification</i>: "<code>const</code>", "<code>volatile</code>",
|
||||
or "<code>const volatile</code>".
|
||||
|
||||
<table border="1" summary="class_ template parameters">
|
||||
<tr>
|
||||
<th>Argument Type</th>
|
||||
|
||||
<th>Behavior</th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>T cv&</code><br>
|
||||
<code>T cv</code></td>
|
||||
|
||||
<td>The Python argument is created by the same means used for the
|
||||
return value of a wrapped C++ function returning <code>T</code>. When
|
||||
<code>T</code> is a class type, that normally means <code>*x</code>
|
||||
is copy-constructed into the new Python object.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>T*</code></td>
|
||||
|
||||
<td>If <code>x == 0</code>, the Python argument will be
|
||||
<code><a href=
|
||||
"http://www.python.org/doc/current/lib/bltin-null-object.html">None</a></code>.
|
||||
Otherwise, the Python argument is created by the same means used for
|
||||
the return value of a wrapped C++ function returning <code>T</code>.
|
||||
When <code>T</code> is a class type, that normally means
|
||||
<code>*x</code> is copy-constructed into the new Python object.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code><a href=
|
||||
"../../../bind/ref.html#reference_wrapper">boost::reference_wrapper</a><T></code></td>
|
||||
|
||||
<td>The Python argument contains a pointer to, rather than a copy of,
|
||||
<code>x.get()</code>. Note: failure to ensure that no Python code
|
||||
holds a reference to the resulting object beyond the lifetime of
|
||||
<code>*x.get()</code> <b>may result in a crash!</b></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code><a href=
|
||||
"ptr.html#pointer_wrapper-spec">pointer_wrapper</a><T></code></td>
|
||||
|
||||
<td>If <code>x.get() == 0</code>, the Python argument will
|
||||
be <code><a href=
|
||||
"http://www.python.org/doc/current/lib/bltin-null-object.html">None</a></code>.
|
||||
Otherwise, the Python argument contains a pointer to, rather than a
|
||||
copy of, <code>*x.get()</code>. Note: failure to ensure that no
|
||||
Python code holds a reference to the resulting object beyond the
|
||||
lifetime of <code>*x.get()</code> <b>may result in a crash!</b></td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h2><a name="result_handling">Result Handling</a></h2>
|
||||
In general, <code>call<ResultType>()</code> and
|
||||
<code>call_method<ResultType>()</code> return
|
||||
<code>ResultType</code> by exploiting all lvalue and rvalue
|
||||
<code>from_python</code> converters registered for ResultType and
|
||||
returning a copy of the result. However, when <code>ResultType</code> is
|
||||
a pointer or reference type, Boost.Python searches only for lvalue
|
||||
converters. To prevent dangling pointers and references, an exception
|
||||
will be thrown if the Python result object has only a single reference
|
||||
count.
|
||||
|
||||
<h2><a name="rationale">Rationale</a></h2>
|
||||
In general, to get Python arguments corresponding to
|
||||
<code>a1</code>...<code>a<i>N</i></code>, a new Python object must be
|
||||
created for each one; should the C++ object be copied into that Python
|
||||
object, or should the Python object simply hold a reference/pointer to
|
||||
the C++ object? In general, the latter approach is unsafe, since the
|
||||
called function may store a reference to the Python object somewhere. If
|
||||
the Python object is used after the C++ object is destroyed, we'll crash
|
||||
Python.
|
||||
|
||||
<p>In keeping with the philosophy that users on the Python side shouldn't
|
||||
have to worry about crashing the interpreter, the default behavior is to
|
||||
copy the C++ object, and to allow a non-copying behavior only if the user
|
||||
writes <code><a href="../../../bind/ref.html">boost::ref</a>(a1)</code>
|
||||
instead of a1 directly. At least this way, the user doesn't get dangerous
|
||||
behavior "by accident". It's also worth noting that the non-copying
|
||||
("by-reference") behavior is in general only available for class types,
|
||||
and will fail at runtime with a Python exception if used otherwise[<a
|
||||
href="#1">1</a>].</p>
|
||||
|
||||
<p>However, pointer types present a problem: one approach is to refuse to
|
||||
compile if any aN has pointer type: after all, a user can always pass
|
||||
<code>*aN</code> to pass "by-value" or <code>ref(*aN)</code> to indicate
|
||||
a pass-by-reference behavior. However, this creates a problem for the
|
||||
expected null pointer to <code>None</code> conversion: it's illegal to
|
||||
dereference a null pointer value.</p>
|
||||
|
||||
<p>The compromise I've settled on is this:</p>
|
||||
|
||||
<ol>
|
||||
<li>The default behavior is pass-by-value. If you pass a non-null
|
||||
pointer, the pointee is copied into a new Python object; otherwise the
|
||||
corresponding Python argument will be None.</li>
|
||||
|
||||
<li>if you want by-reference behavior, use <code>ptr(aN)</code> if
|
||||
<code>aN</code> is a pointer and <code>ref(aN)</code> otherwise. If a
|
||||
null pointer is passed to <code>ptr(aN)</code>, the corresponding
|
||||
Python argument will be <code>None</code>.</li>
|
||||
</ol>
|
||||
|
||||
<p>As for results, we have a similar problem: if <code>ResultType</code>
|
||||
is allowed to be a pointer or reference type, the lifetime of the object
|
||||
it refers to is probably being managed by a Python object. When that
|
||||
Python object is destroyed, our pointer dangles. The problem is
|
||||
particularly bad when the <code>ResultType</code> is char const* - the
|
||||
corresponding Python String object is typically uniquely-referenced,
|
||||
meaning that the pointer dangles as soon as <code>call<char
|
||||
const*>(...)</code> returns.</p>
|
||||
|
||||
<p>The old Boost.Python v1 deals with this issue by refusing to compile
|
||||
any uses of <code>call<char const*>()</code>, but this goes both
|
||||
too far and not far enough. It goes too far because there are cases where
|
||||
the owning Python string object survives beyond the call (just for
|
||||
instance, when it's the name of a Python class), and it goes not far
|
||||
enough because we might just as well have the same problem with a
|
||||
returned pointer or reference of any other type.</p>
|
||||
|
||||
<p>In Boost.Python v2 this is dealt with by:</p>
|
||||
|
||||
<ol>
|
||||
<li>lifting the compile-time restriction on const char* callback
|
||||
returns</li>
|
||||
|
||||
<li>detecting the case when the reference count on the result Python
|
||||
object is 1 and throwing an exception inside of
|
||||
<code>call<U>(...)</code> when <code>U</code> is a pointer or
|
||||
reference type.</li>
|
||||
</ol>
|
||||
This should be acceptably safe because users have to explicitly specify a
|
||||
pointer/reference for <code>U</code> in <code>call<U></code>, and
|
||||
they will be protected against dangles at runtime, at least long enough
|
||||
to get out of the <code>call<U>(...)</code> invocation.
|
||||
<hr>
|
||||
<a name="1">[1]</a> It would be possible to make it fail at compile-time
|
||||
for non-class types such as int and char, but I'm not sure it's a good
|
||||
idea to impose this restriction yet.
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,88 +0,0 @@
|
||||
Here's the plan:
|
||||
|
||||
I aim to provide an interface similar to that of Boost.Python v1's
|
||||
callback<>::call(...) for dealing with callbacks. The interface will
|
||||
look like:
|
||||
|
||||
returning<ResultType>::call("method_name", self_object, a1, a2...);
|
||||
|
||||
or
|
||||
|
||||
returning<ResultType>::call(callable_object, a1, a2...);
|
||||
|
||||
ARGUMENT HANDLING
|
||||
|
||||
There is an issue concerning how to make Python objects from the
|
||||
arguments a1...aN. A new Python object must be created; should the C++
|
||||
object be copied into that Python object, or should the Python object
|
||||
simply hold a reference/pointer to the C++ object? In general, the
|
||||
latter approach is unsafe, since the called function may store a
|
||||
reference to the Python object somewhere. If the Python object is used
|
||||
after the C++ object is destroyed, we'll crash Python.
|
||||
|
||||
I plan to make the copying behavior the default, and to allow a
|
||||
non-copying behavior if the user writes boost::ref(a1) instead of a1
|
||||
directly. At least this way, the user doesn't get dangerous behavior "by
|
||||
accident". It's also worth noting that the non-copying ("by-reference")
|
||||
behavior is in general only available for class types, and will fail at
|
||||
runtime with a Python exception if used otherwise**
|
||||
|
||||
However, pointer types present a problem: My first thought is to refuse
|
||||
to compile if any aN has pointer type: after all, a user can always pass
|
||||
*aN to pass "by-value" or ref(*aN) to indicate a pass-by-reference
|
||||
behavior. However, this creates a problem for the expected NULL pointer
|
||||
=> None conversion: it's illegal to dereference a null pointer value.
|
||||
|
||||
We could use another construct, say "ptr(aN)", to deal with null
|
||||
pointers, but then what does it mean? We know what it does when aN is
|
||||
NULL, but it might either have by-value or by-reference behavior when aN
|
||||
is non-null.
|
||||
|
||||
The compromise I've settled on is this:
|
||||
|
||||
1. The default behavior is pass-by-value. If you pass a non-null
|
||||
pointer, the pointee is copied into a new Python object; otherwise
|
||||
the corresponding Python argument will be None.
|
||||
|
||||
2. if you want by-reference behavior, use ptr(aN) if aN is a pointer
|
||||
and ref(aN) otherwise. If a null pointer is passed to ptr(aN), the
|
||||
corresponding Python argument will be None.
|
||||
|
||||
RESULT HANDLING
|
||||
|
||||
As for results, we have a similar problem: if ResultType is allowed to
|
||||
be a pointer or reference type, the lifetime of the object it refers to
|
||||
is probably being managed by a Python object. When that Python object is
|
||||
destroyed, our pointer dangles. The problem is particularly bad when the
|
||||
ResultType is char const* - the corresponding Python String object is
|
||||
typically uniquely-referenced, meaning that the pointer dangles as soon
|
||||
as returning<char const*>::call() returns.
|
||||
|
||||
Boost.Python v1 deals with this issue by refusing to compile any uses of
|
||||
callback<char const*>::call(), but IMO this goes both too far and not
|
||||
far enough. It goes too far because there are cases where the owning
|
||||
String object survives beyond the call (just for instance when it's the
|
||||
name of a Python class), and it goes not far enough because we might
|
||||
just as well have the same problem with any returned pointer or
|
||||
reference.
|
||||
|
||||
I propose to address this in Boost.Python v2 by
|
||||
|
||||
1. lifting the compile-time restriction on const
|
||||
char* callback returns
|
||||
|
||||
2. detecting the case when the reference count on the
|
||||
result Python object is 1 and throwing an exception
|
||||
inside of returning<U>::call() when U is a pointer or
|
||||
reference type.
|
||||
|
||||
I think this is acceptably safe because users have to explicitly specify
|
||||
a pointer/reference for U in returning<U>, and they will be protected
|
||||
against dangles at runtime, at least long enough to get out of the
|
||||
returning<U>::call() invocation.
|
||||
|
||||
-Dave
|
||||
|
||||
**It would be possible to make it fail at compile-time for non-class
|
||||
types such as int and char, but I'm not sure it's a good idea to impose
|
||||
this restriction yet.
|
||||
@@ -1,785 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/class.hpp>,
|
||||
<boost/python/class_fwd.hpp></title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Headers <boost/python/class.hpp>,
|
||||
<boost/python/class_fwd.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#class_-spec">Class template
|
||||
<code>class_</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#class_-spec-synopsis">Class <code>class_</code>
|
||||
synopsis</a></dt>
|
||||
|
||||
<dt><a href="#class_-spec-ctors">Class <code>class_</code>
|
||||
constructors</a></dt>
|
||||
|
||||
<dt><a href="#class_-spec-modifiers">Class <code>class_</code>
|
||||
modifier functions</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#bases-spec">Class template
|
||||
<code>bases</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#bases-spec-synopsis">Class template
|
||||
<code>bases</code> synopsis</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><code><boost/python/class.hpp></code> defines the interface
|
||||
through which users expose their C++ classes to Python. It declares the
|
||||
<code>class_</code> class template, which is parameterized on the class
|
||||
type being exposed. It also exposes the <code>init</code>,
|
||||
<code>optional</code> and <code>bases</code> utility class templates,
|
||||
which are used in conjunction with <code>class_</code>.</p>
|
||||
|
||||
<p><code><boost/python/class_fwd.hpp></code> contains a forward
|
||||
declaration of the <code>class_</code> class template.</p>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="class_-spec"></a>Class template
|
||||
<code>class_<T, <font color="#007F00">Bases, HeldType,
|
||||
NonCopyable</font>></code></h3>
|
||||
|
||||
<p>Creates a Python class associated with the C++ type passed as its
|
||||
first parameter. Although it has four template parameters, only the first
|
||||
one is required. The three optional arguments can actually be supplied
|
||||
<font color="#007F00"><b>in any order</b></font>; Boost.Python determines
|
||||
the role of the argument from its type.<br>
|
||||
<br>
|
||||
</p>
|
||||
|
||||
<table border="1" summary="class_ template parameters">
|
||||
<tr>
|
||||
<th>Template Parameter</th>
|
||||
|
||||
<th>Requirements</th>
|
||||
|
||||
<th>Semantics</th>
|
||||
|
||||
<th>Default</th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code>T</code></td>
|
||||
|
||||
<td>A class type.</td>
|
||||
|
||||
<td>The class being wrapped</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code><font color="#007F00">Bases</font></code></td>
|
||||
|
||||
<td>A specialization of <a href=
|
||||
"#bases-spec"><code>bases<</code>...<code>></code></a> which
|
||||
specifies previously-exposed C++ base classes of <code>T</code><a
|
||||
href="#footnote_1">[1]</a>.</td>
|
||||
|
||||
<td>Registers <code>from_python</code> conversions from wrapped
|
||||
<code>T</code> instances to each of its exposed direct and indirect
|
||||
bases. For each polymorphic base <code>B</code>, registers
|
||||
conversions from indirectly-held wrapped <code>B</code> instances to
|
||||
<code>T</code>.</td>
|
||||
|
||||
<td><code><a href="#bases">bases<></a></code></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code><font color="#007F00">HeldType</font></code></td>
|
||||
|
||||
<td>Must be <code>T</code>, a class derived from <code>T</code>, or a
|
||||
<a href="Dereferenceable.html">Dereferenceable</a> type for which
|
||||
<code><a href=
|
||||
"pointee.html#pointee-spec">pointee</a><HeldType>::type</code>
|
||||
is <code>T</code> or a class derived from <code>T</code>.</td>
|
||||
|
||||
<td>Specifies the type which is actually embedded in a Python object
|
||||
wrapping a <code>T</code> instance. More details <a href=
|
||||
"#HeldType">below</a>.</td>
|
||||
|
||||
<td><code>T</code></td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td><code><font color="#007F00">NonCopyable</font></code></td>
|
||||
|
||||
<td>If supplied, must be <a href=
|
||||
"../../../utility/utility.htm#Class%20noncopyable">boost::noncopyable</a>.</td>
|
||||
|
||||
<td>Suppresses automatic registration of <code>to_python</code>
|
||||
conversions which copy <code>T</code> instances. Required when
|
||||
<code>T</code> has no publicly-accessible copy constructor.</td>
|
||||
|
||||
<td>An unspecified type other than
|
||||
<code>boost::noncopyable</code>.</td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h4><a name="#HeldType">HeldType Semantics</a></h4>
|
||||
|
||||
<ol>
|
||||
<li>If <code>HeldType</code> is derived from T, its exposed
|
||||
constructor(s) must accept an initial <code>PyObject*</code> argument
|
||||
which refers back to the Python object that contains the
|
||||
<code>HeldType</code> instance, as shown in <a href=
|
||||
"call_method.html#example">this example</a>. This argument is not
|
||||
included in the <em><a href=
|
||||
"init.html#init-expressions">init-expression</a></em> passed to <a
|
||||
href="#class-spec-modifiers"><code>def(init_expr)</code></a>, below,
|
||||
nor is it passed explicitly by users when Python instances of
|
||||
<code>T</code> are created. This idiom allows C++ virtual functions
|
||||
which will be overridden in Python to access the Python object so the
|
||||
Python method can be invoked. Boost.Python automatically registers
|
||||
additional converters which allow wrapped instances of <code>T</code>
|
||||
to be passed to wrapped C++ functions expecting <code>HeldType</code>
|
||||
arguments.</li>
|
||||
|
||||
<li>Because Boost.Python will always allow wrapped instances of
|
||||
<code>T</code> to be passed in place of <code>HeldType</code>
|
||||
arguments, specifying a smart pointer for <code>HeldType</code> allows
|
||||
users to pass Python <code>T</code> instances where a smart
|
||||
pointer-to-<code>T</code> is expected. Smart pointers such as
|
||||
<code>std::auto_ptr<></code> or <code><a href=
|
||||
"../../../smart_ptr/shared_ptr.htm">boost::shared_ptr<></a></code>
|
||||
which contain a nested type <code>element_type</code> designating the
|
||||
referent type are automatically supported; additional smart pointer
|
||||
types can be supported by specializing <a href=
|
||||
"pointee.html#pointee-spec">pointee<HeldType></a>.</li>
|
||||
|
||||
<li>As in case 1 above, when <code>HeldType</code> is a smart pointer
|
||||
to a class derived from <code>T</code>, the initial
|
||||
<code>PyObject*</code> argument must be supplied by all of
|
||||
<code>HeldType</code>'s exposed constructors.</li>
|
||||
|
||||
<li>Except in cases 1 and 3, users may optionally specify that T itself
|
||||
gets initialized with a similar initial <code>PyObject*</code> argument
|
||||
by specializing <a href=
|
||||
"has_back_reference.html#has_back_reference-spec">has_back_reference<T></a>.</li>
|
||||
</ol>
|
||||
|
||||
<h4><a name="class_-spec-synopsis"></a>Class template <code>class_</code>
|
||||
synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
template <class T
|
||||
<font color="#007F00"> , class Bases = bases<>
|
||||
, class HeldType = T
|
||||
, class NonCopyable = <i>unspecified</i>
|
||||
>
|
||||
</font> class class_ : public <a href="object.html#object-spec">object</a>
|
||||
{
|
||||
// Constructors with default __init__
|
||||
class_(char const* name);
|
||||
class_(char const* name, char const* docstring);
|
||||
|
||||
// Constructors, specifying non-default __init__
|
||||
template <class Init>
|
||||
class_(char const* name, Init);
|
||||
template <class Init>
|
||||
class_(char const* name, char const* docstring, Init);
|
||||
|
||||
// Exposing additional __init__ functions
|
||||
template <class Init>
|
||||
class_& def(Init);
|
||||
|
||||
// defining methods
|
||||
template <class F>
|
||||
class_& def(char const* name, F f);
|
||||
template <class Fn, class A1>
|
||||
class_& def(char const* name, Fn fn, A1 const&);
|
||||
template <class Fn, class A1, class A2>
|
||||
class_& def(char const* name, Fn fn, A1 const&, A2 const&);
|
||||
template <class Fn, class A1, class A2, class A3>
|
||||
class_& def(char const* name, Fn fn, A1 const&, A2 const&, A3 const&);
|
||||
|
||||
// declaring method as static
|
||||
class_& staticmethod(char const* name);
|
||||
|
||||
// exposing operators
|
||||
template <<i>unspecified</i>>
|
||||
class_& def(<a href=
|
||||
"operators.html#operator_-spec">detail::operator_</a><unspecified>);
|
||||
|
||||
// Raw attribute modification
|
||||
template <class U>
|
||||
class_& setattr(char const* name, U const&);
|
||||
|
||||
// exposing data members
|
||||
template <class D>
|
||||
class_& def_readonly(char const* name, D T::*pm);
|
||||
|
||||
template <class D>
|
||||
class_& def_readwrite(char const* name, D T::*pm);
|
||||
|
||||
// exposing static data members
|
||||
template <class D>
|
||||
class_& def_readonly(char const* name, D const& d);
|
||||
template <class D>
|
||||
class_& def_readwrite(char const* name, D& d);
|
||||
|
||||
// property creation
|
||||
template <class Get>
|
||||
void add_property(char const* name, Get const& fget);
|
||||
template <class Get, class Set>
|
||||
void add_property(char const* name, Get const& fget, Set const& fset);
|
||||
|
||||
template <class Get>
|
||||
void add_static_property(char const* name, Get const& fget);
|
||||
template <class Get, class Set>
|
||||
void add_static_property(char const* name, Get const& fget, Set const& fset);
|
||||
|
||||
// pickle support
|
||||
template <typename PickleSuite>
|
||||
self& def_pickle(PickleSuite const&);
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="class_-spec-ctors"></a>Class template <code>class_</code>
|
||||
constructors</h4>
|
||||
<pre>
|
||||
class_(char const* name);
|
||||
class_(char const* name, char const* docstring);
|
||||
template <class Init>
|
||||
class_(char const* name, Init init_spec);
|
||||
template <class Init>
|
||||
class_(char const* name, char const* docstring, Init init_spec);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>. If <code>docstring</code> is supplied, it must be an
|
||||
<a href="definitions.html#ntbs">ntbs</a>. If <code>init_spec</code> is
|
||||
supplied, it must be either the special enumeration constant
|
||||
<code>no_init</code> or an <a href=
|
||||
"init.html#init-expression">init-expression</a> compatible with
|
||||
<code>T</code>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Constructs a <code>class_</code> object holding a
|
||||
Boost.Python extension class named <code>name</code>. The
|
||||
<code>name</code>d attribute of the <a href=
|
||||
"scope.html#introduction">current scope</a> is bound to the new
|
||||
extension class.</dt>
|
||||
|
||||
<dd>
|
||||
<ul>
|
||||
<li>If supplied, the value of <code>docstring</code> is bound to
|
||||
the <code>__doc__</code> attribute of the extension class.</li>
|
||||
|
||||
<li>If <code>init_spec</code> is <code>no_init</code>, a special
|
||||
<code>__init__</code> function is generated which always raises a
|
||||
Python exception. Otherwise, <code>this->def(init_spec)</code>
|
||||
is called.</li>
|
||||
|
||||
<li>If <code>init_spec</code> is not supplied,
|
||||
<code>this->def(init<>())</code> is called.</li>
|
||||
</ul>
|
||||
</dd>
|
||||
|
||||
<dt><b>Rationale:</b>Allowing the user to specify constructor arguments
|
||||
in the <code>class_<></code> constructor helps her to avoid the
|
||||
common run-time errors which result from invoking wrapped member
|
||||
functions without having exposed an <code>__init__</code> function
|
||||
which creates the requisite <code>T</code> instance. Types which are
|
||||
not default-constructible will cause a compile-time error unless
|
||||
<code>Init</code> is supplied. The user must always supply
|
||||
<code>name</code> as there is currently no portable method to derive
|
||||
the text of the class name from its type.</dt>
|
||||
</dl>
|
||||
|
||||
<h4><a name="class_-spec-modifiers"></a>Class template
|
||||
<code>class_</code> modifier functions</h4>
|
||||
<pre>
|
||||
template <class Init>
|
||||
class_& def(Init init_expr);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>init_expr</code> is the result of an <a
|
||||
href="init.html#init-expression">init-expression</a> compatible with
|
||||
<code>T</code>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> For each <a href="init.html#init-expressions">valid
|
||||
prefix</a> <em>P</em> of <code>Init</code>, adds an
|
||||
<code>__init__(</code>...<code>)</code> function overload to the
|
||||
extension class accepting <em>P</em> as arguments. Each overload
|
||||
generated constructs an object of <code>HeldType</code> according to
|
||||
the semantics described <a href="#HeldType">above</a>, using a copy of
|
||||
<code>init_expr</code>'s <a href="CallPolicies.html">call policies</a>.
|
||||
If the longest <a href="init.html#init-expressions">valid prefix</a> of
|
||||
<code>Init</code> contains <em>N</em> types and <code>init_expr</code>
|
||||
holds <em>M</em> keywords, an initial sequence of the keywords are used
|
||||
for all but the first <em>N</em> - <em>M</em> arguments of
|
||||
each overload.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
<dt><b>Rationale:</b> Allows users to easily expose a class'
|
||||
constructor to Python.</dt>
|
||||
</dl>
|
||||
<br>
|
||||
|
||||
<pre>
|
||||
template <class F>
|
||||
class_& def(char const* name, Fn fn);
|
||||
template <class Fn, class A1>
|
||||
class_& def(char const* name, Fn fn, A1 const& a1);
|
||||
template <class Fn, class A1, class A2>
|
||||
class_& def(char const* name, Fn fn, A1 const& a1, A2 const& a2);
|
||||
template <class Fn, class A1, class A2, class A3>
|
||||
class_& def(char const* name, Fn fn, A1 const& a1, A2 const& a2, A3 const& a3);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.</dt>
|
||||
|
||||
<dd>
|
||||
<ul>
|
||||
<li>
|
||||
If <code>a1</code> is the result of an <a href=
|
||||
"overloads.html#overload-dispatch-expression"><em>overload-dispatch-expression</em></a>,
|
||||
only the second form is allowed and fn must be a pointer to
|
||||
function or pointer to member function whose <a href=
|
||||
"definitions.html#arity">arity</a> is the same as A1's <a href=
|
||||
"overloads.html#overload-dispatch-expression"><em>maximum
|
||||
arity</em></a>.
|
||||
|
||||
<dl>
|
||||
<dt><b>Effects:</b> For each prefix <em>P</em> of
|
||||
<code>Fn</code>'s sequence of argument types, beginning with
|
||||
the one whose length is <code>A1</code>'s <a href=
|
||||
"overloads.html#overload-dispatch-expression"><em>minimum
|
||||
arity</em></a>, adds a
|
||||
<code><em>name</em>(</code>...<code>)</code> method overload to
|
||||
the extension class. Each overload generated invokes
|
||||
<code>a1</code>'s call-expression with <em>P</em>, using a copy
|
||||
of <code>a1</code>'s <a href="CallPolicies.html">call
|
||||
policies</a>. If the longest valid prefix of <code>A1</code>
|
||||
contains <em>N</em> types and <code>a1</code> holds <em>M</em>
|
||||
keywords, an initial sequence of the keywords are used for all
|
||||
but the first <em>N</em> - <em>M</em> arguments of
|
||||
each overload.<br>
|
||||
</dt>
|
||||
</dl>
|
||||
</li>
|
||||
|
||||
<li>
|
||||
Otherwise, a single method overload is built around fn, which
|
||||
must not be null:
|
||||
|
||||
<ul>
|
||||
<li>If fn is a function pointer, its first argument must be of
|
||||
the form <code>U</code>, <code>U <em>cv</em>&</code>,
|
||||
<code>U <em>cv</em>*</code>, or
|
||||
<code>U <em>cv</em>* const&</code>, where
|
||||
<code>T*</code> is convertible to <code>U*</code>, and
|
||||
<code>a1</code>-<code>a3</code>, if supplied, may be selected
|
||||
in any order from the table below.</li>
|
||||
|
||||
<li>Otherwise, if fn is a member function pointer, its target
|
||||
must be <code>T</code> or one of its public base classes, and
|
||||
<code>a1</code>-<code>a3</code>, if supplied, may be selected
|
||||
in any order from the table below.</li>
|
||||
|
||||
<li>Otherwise, <code>Fn</code> must be [derived from] <code><a
|
||||
href="object.html#object-spec">object</a></code>, and
|
||||
<code>a1-a2</code>, if supplied, may be selcted in any order
|
||||
from the first two rows of the table below. To be useful,
|
||||
<code>fn</code> should be <a href=
|
||||
"http://www.python.org/doc/current/lib/built-in-funcs.html#l2h-6">
|
||||
callable</a>.</li>
|
||||
</ul>
|
||||
|
||||
<table border="1" summary="def() optional arguments">
|
||||
<tr>
|
||||
<th>Memnonic Name</th>
|
||||
|
||||
<th>Requirements/Type properties</th>
|
||||
|
||||
<th>Effects</th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>docstring</td>
|
||||
|
||||
<td>Any <a href="definitions.html#ntbs">ntbs</a>.</td>
|
||||
|
||||
<td>Value will be bound to the <code>__doc__</code> attribute
|
||||
of the resulting method overload.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>policies</td>
|
||||
|
||||
<td>A model of <a href=
|
||||
"CallPolicies.html">CallPolicies</a></td>
|
||||
|
||||
<td>A copy will be used as the call policies of the resulting
|
||||
method overload.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>keywords</td>
|
||||
|
||||
<td>The result of a <a href=
|
||||
"args.html#keyword-expression"><em>keyword-expression</em></a>
|
||||
specifying no more arguments than the <a href=
|
||||
"definitions.html#arity">arity</a> of <code>fn</code>.</td>
|
||||
|
||||
<td>A copy will be used as the call policies of the resulting
|
||||
method overload.</td>
|
||||
</tr>
|
||||
</table>
|
||||
</li>
|
||||
</ul>
|
||||
</dd>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
</dl>
|
||||
<pre>
|
||||
class_& staticmethod(char const* name);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>, and corresponds to a method whose overloads have all
|
||||
been defined.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Replaces the existing named attribute <i>x</i> with
|
||||
the result of invoking <code>staticmethod(</code><i>x</i><code>)</code>
|
||||
in Python. Specifies that the corresponding method is static and
|
||||
therefore no object instance will be passed to it. This is equivalent
|
||||
to the Python statement:</dt>
|
||||
|
||||
<dd>
|
||||
<pre>
|
||||
setattr(self, name, staticmethod(getattr(self, name)))
|
||||
</pre>
|
||||
</dd>
|
||||
|
||||
<dt><b>Note:</b> Attempting to invoke <code>def(name,...)</code> after
|
||||
invoking <code>staticmethod(name)</code> will <a href=
|
||||
"definitions.html#raise">raise</a> a RuntimeError.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
</dl>
|
||||
<br>
|
||||
|
||||
<pre>
|
||||
template <<i>unspecified</i>>
|
||||
class_& def(<a href=
|
||||
"operators.html#operator_-spec">detail::operator_</a><unspecified>);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Effects:</b> Adds a Python <a href=
|
||||
"http://www.python.org/doc/ref/specialnames.html">special method</a> as
|
||||
described <a href="operators.html">here</a>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
</dl>
|
||||
<pre>
|
||||
template <class U>
|
||||
class_& setattr(char const* name, U const& u);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Converts u to Python and adds it to the attribute
|
||||
dictionary of the extension class:</dt>
|
||||
|
||||
<dd>
|
||||
<blockquote>
|
||||
<code><a href=
|
||||
"http://www.python.org/doc/current/api/object.html#l2h-166">PyObject_SetAttrString</a>(this->ptr(), name, <a
|
||||
href="object.html#object-spec-ctors">object</a>(u).ptr());</code>
|
||||
</blockquote>
|
||||
</dd>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
</dl>
|
||||
<br>
|
||||
|
||||
<pre>
|
||||
template <class Get>
|
||||
void add_property(char const* name, Get const& fget);
|
||||
template <class Get, class Set>
|
||||
void add_property(char const* name, Get const& fget, Set const& fset);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Creates a new Python <a href=
|
||||
"http://www.python.org/2.2.2/descrintro.html#property"><code>property</code></a>
|
||||
class instance, passing <code><a href=
|
||||
"object.html#object-spec-ctors">object</a>(fget)</code> (and <code><a
|
||||
href="object.html#object-spec-ctors">object</a>(fset)</code> in the
|
||||
second form) to its constructor, then adds that property to the Python
|
||||
class object under construction with the given attribute
|
||||
<code>name</code>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
<dt><b>Rationale:</b> Allows users to easily expose functions that can
|
||||
be invoked from Python with attribute access syntax.</dt>
|
||||
</dl>
|
||||
<br>
|
||||
<pre>
|
||||
template <class Get>
|
||||
void add_static_property(char const* name, Get const& fget);
|
||||
template <class Get, class Set>
|
||||
void add_static_property(char const* name, Get const& fget, Set const& fset);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Creates a Boost.Python.StaticProperty object,
|
||||
passing <code><a href=
|
||||
"object.html#object-spec-ctors">object</a>(fget)</code> (and <code><a
|
||||
href="object.html#object-spec-ctors">object</a>(fset)</code> in the
|
||||
second form) to its constructor, then adds that property to the Python
|
||||
class under construction with the given attribute <code>name</code>.
|
||||
StaticProperty is a special subclass of Python's <a href=
|
||||
"http://www.python.org/2.2.2/descrintro.html#property"><code>property</code></a>
|
||||
class which can be called without an initial <code>self</code>
|
||||
argument.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
<dt><b>Rationale:</b> Allows users to easily expose functions that can
|
||||
be invoked from Python with static attribute access syntax.</dt>
|
||||
</dl>
|
||||
<br>
|
||||
<pre>
|
||||
template <class D>
|
||||
class_& def_readonly(char const* name, D T::*pm);
|
||||
template <class D>
|
||||
class_& def_readonly(char const* name, D const& d);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b></dt>
|
||||
|
||||
<dd>
|
||||
<pre>
|
||||
this->add_property(name, <a href=
|
||||
"data_members.html#make_getter-spec">make_getter</a>(pm));
|
||||
</pre>
|
||||
and
|
||||
<pre>
|
||||
this->add_static_property(name, <a href=
|
||||
"data_members.html#make_getter-spec">make_getter</a>(pm));
|
||||
</pre>
|
||||
respectively.<br>
|
||||
<br>
|
||||
</dd>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
<dt><b>Rationale:</b> Allows users to easily expose a class' data
|
||||
member or free variable such that it can be inspected from Python with
|
||||
a natural syntax.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
template <class D>
|
||||
class_& def_readwrite(char const* name, D T::*pm);
|
||||
template <class D>
|
||||
class_& def_readwrite(char const* name, D& d);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Effects:</b></dt>
|
||||
|
||||
<dd>
|
||||
<pre>
|
||||
this->add_property(name, <a href=
|
||||
"data_members.html#make_getter-spec">make_getter</a>(pm), <a href=
|
||||
"data_members.html#make_setter-spec">make_setter</a>(pm));
|
||||
</pre>
|
||||
and
|
||||
<pre>
|
||||
this->add_static_property(name, <a href=
|
||||
"data_members.html#make_getter-spec">make_getter</a>(pm), <a href=
|
||||
"data_members.html#make_setter-spec">make_setter</a>(pm));
|
||||
</pre>
|
||||
respectively.<br>
|
||||
<br>
|
||||
</dd>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
<dt><b>Rationale:</b> Allows users to easily expose a class' data or
|
||||
free variable member such that it can be inspected and set from Python
|
||||
with a natural syntax.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
template <typename PickleSuite>
|
||||
class_& def_pickle(PickleSuite const&);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> PickleSuite must be publically derived from <a
|
||||
href="pickle.html"><code>pickle_suite</code></a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Defines a legal combination of the special
|
||||
attributes and methods: <code>__getinitargs__</code>,
|
||||
<code>__getstate__</code>, <code>__setstate__</code>,
|
||||
<code>__getstate_manages_dict__</code>,
|
||||
<code>__safe_for_unpickling__</code>, <code>__reduce__</code></dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
<dt><b>Rationale:</b> Provides an <a href="pickle.html">easy to use
|
||||
high-level interface</a> for establishing complete pickle support for
|
||||
the wrapped class. The user is protected by compile-time consistency
|
||||
checks.</dt>
|
||||
</dl>
|
||||
<br>
|
||||
|
||||
|
||||
<h3><a name="bases-spec"></a>Class template
|
||||
<code>bases<T1, T2,</code>...<code>TN></code></h3>
|
||||
|
||||
<p>An <a href="../../../mpl/doc/ref/Sequences.html">MPL sequence</a>
|
||||
which can be used in <code>class_<</code>...<code>></code>
|
||||
instantiations indicate a list of base classes.</p>
|
||||
|
||||
<h4><a name="bases-spec-synopsis"></a>Class template <code>bases</code>
|
||||
synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
template <T1 = <i>unspecified</i>,...T<i>n</i> = <i>unspecified</i>>
|
||||
struct bases
|
||||
{};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h2><a name="examples"></a>Example(s)</h2>
|
||||
|
||||
<p>Given a C++ class declaration:</p>
|
||||
<pre>
|
||||
class Foo : public Bar, public Baz
|
||||
{
|
||||
public:
|
||||
Foo(int x, char const* y);
|
||||
Foo(double);
|
||||
|
||||
std::string const& name() { return m_name; }
|
||||
void name(char const*);
|
||||
|
||||
double value; // public data
|
||||
private:
|
||||
...
|
||||
};
|
||||
</pre>
|
||||
A corresponding Boost.Python extension class can be created with:
|
||||
<pre>
|
||||
using namespace boost::python;
|
||||
|
||||
class_<Foo,bases<Bar,Baz> >("Foo",
|
||||
"This is Foo's docstring."
|
||||
"It describes our Foo extension class",
|
||||
|
||||
init<int,char const*>(args("x","y"), "__init__ docstring")
|
||||
)
|
||||
.def(init<double>())
|
||||
.def("get_name", &Foo::get_name, return_internal_reference<>())
|
||||
.def("set_name", &Foo::set_name)
|
||||
.def_readwrite("value", &Foo::value)
|
||||
;
|
||||
</pre>
|
||||
<hr>
|
||||
<a name="footnote_1">[1]</a> By "previously-exposed" we mean that the for
|
||||
each <code>B</code> in <code>bases</code>, an instance of
|
||||
<code>class_<B<font color="#007F00">, ...</font>></code> must have
|
||||
already been constructed.
|
||||
<pre>
|
||||
class_<Base>("Base");
|
||||
class_<Derived, bases<Base> >("Derived");
|
||||
</pre>
|
||||
Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
5 August, 2002 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,153 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - Configuration</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Configuration</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#app-defined">Application Defined Macros</a></dt>
|
||||
|
||||
<dt><a href="#lib-defined-impl">Library Defined Implementation
|
||||
Macros</a></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><b>Boost.Python</b> uses several configuration macros in <a href=
|
||||
"http://www.boost.org/libs/config/config.htm"><boost/config.hpp></a>,
|
||||
as well as configuration macros meant to be supplied by the application.
|
||||
These macros are documented here.</p>
|
||||
|
||||
<h2><a name="app-defined"></a>Application Defined Macros</h2>
|
||||
|
||||
<p>These are the macros that may be defined by an application using
|
||||
<b>Boost.Python</b>. Note that if you extend a strict interpretation of
|
||||
the C++ standard to cover dynamic libraries, using different values of
|
||||
these macros when compiling different libraries (including extension
|
||||
modules and the <b>Boost.Python</b> library itself) is a violation of the
|
||||
<a href="definitions.html#ODR">ODR</a>. However, we know of no C++
|
||||
implementations on which this particular violation is detectable or
|
||||
causes any problems.</p>
|
||||
|
||||
<table summary="application defined macros" width="100%" cellpadding=
|
||||
"10">
|
||||
<tr>
|
||||
<th align="left"><b>Macro</b></th>
|
||||
|
||||
<th><b>Default</b></th>
|
||||
|
||||
<th align="left"><b>Meaning</b></th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>BOOST_PYTHON_MAX_ARITY</code></td>
|
||||
|
||||
<td valign="top" align="center">15</td>
|
||||
|
||||
<td valign="top">The maximum <a href=
|
||||
"definitions.html#arity">arity</a> of any function, member function,
|
||||
or constructor to be wrapped, invocation of a <b>Boost.Python</b>
|
||||
function wich is specified as taking arguments
|
||||
<code>x1, x2,</code>...<code>X</code><i>n</i>. This includes, in
|
||||
particular, callback mechanisms such as <code><a href=
|
||||
"object.html#object-spec">object</a>::operator()(</code>...<code>)</code>
|
||||
or <code><a href=
|
||||
"call_method.html#call_method-spec">call_method</a><R>(</code>...
|
||||
<code>)</code>.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>BOOST_PYTHON_MAX_BASES</code></td>
|
||||
|
||||
<td valign="top" align="center">10</td>
|
||||
|
||||
<td valign="top">The maximum number of template arguments to the
|
||||
<code><a href=
|
||||
"class.html#bases-spec">bases</a><</code>...<code>></code>
|
||||
class template, which is used to specify the bases of a wrapped C++
|
||||
class..</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>BOOST_PYTHON_STATIC_MODULE</code></td>
|
||||
|
||||
<td valign="top" align="center"><i>not defined</i></td>
|
||||
|
||||
<td valign="top">If defined, prevents your module initialization
|
||||
function from being treated as an exported symbol on platforms which
|
||||
support that distinction in-code</td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h2><a name="lib-defined-impl"></a>Library Defined Implementation
|
||||
Macros</h2>
|
||||
|
||||
<p>These macros are defined by <b>Boost.Python</b> and are implementation
|
||||
details of interest only to implementors and those porting to new
|
||||
platforms.</p>
|
||||
|
||||
<table summary="library defined implementation macros" width="100%"
|
||||
cellpadding="10">
|
||||
<tr>
|
||||
<th align="left"><b>Macro</b></th>
|
||||
|
||||
<th><b>Default</b></th>
|
||||
|
||||
<th align="left"><b>Meaning</b></th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td valign="top"><code>BOOST_PYTHON_TYPE_ID_NAME</code></td>
|
||||
|
||||
<td valign="top" align="center"><i>not defined</i></td>
|
||||
|
||||
<td valign="top">If defined, this indicates that the type_info
|
||||
comparison across shared library boundaries does not work on this
|
||||
platform. In other words, if shared-lib-1 passes
|
||||
<code>typeid(T)</code> to a function in shared-lib-2 which compares
|
||||
it to <code>typeid(T)</code>, that comparison may return
|
||||
<code>false</code>. If this macro is #defined, Boost.Python uses and
|
||||
compares <code>typeid(T).name()</code> instead of using and comparing
|
||||
the <code>std::type_info</code> objects directly.</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
7 January, 2003
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,147 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python -
|
||||
<boost/python/copy_const_reference.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header
|
||||
<boost/python/copy_const_reference.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#copy_const_reference-spec">Class
|
||||
<code>copy_const_reference</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#copy_const_reference-spec-synopsis">Class
|
||||
<code>copy_const_reference</code> synopsis</a></dt>
|
||||
|
||||
<dt><a href="#copy_const_reference-spec-metafunctions">Class
|
||||
<code>copy_const_reference</code> metafunctions</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="copy_const_reference-spec"></a>Class
|
||||
<code>copy_const_reference</code></h3>
|
||||
|
||||
<p><code>copy_const_reference</code> is a model of <a href=
|
||||
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a>
|
||||
which can be used to wrap C++ functions returning a reference-to-const
|
||||
type such that the referenced value is copied into a new Python
|
||||
object.</p>
|
||||
|
||||
<h4><a name="copy_const_reference-spec-synopsis"></a>Class
|
||||
<code>copy_const_reference</code> synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
struct copy_const_reference
|
||||
{
|
||||
template <class T> struct apply;
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="copy_const_reference-spec-metafunctions"></a>Class
|
||||
<code>copy_const_reference</code> metafunctions</h4>
|
||||
<pre>
|
||||
template <class T> struct apply
|
||||
</pre>
|
||||
|
||||
<dl class="metafunction-semantics">
|
||||
<dt><b>Requires:</b> <code>T</code> is <code>U const&</code> for
|
||||
some <code>U</code>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>typedef <a href=
|
||||
"to_python_value.html#to_python_value-spec">to_python_value</a><T>
|
||||
type;</code></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
|
||||
<h3>C++ Module Definition</h3>
|
||||
<pre>
|
||||
#include <boost/python/module.hpp>
|
||||
#include <boost/python/class.hpp>
|
||||
#include <boost/python/copy_const_reference.hpp>
|
||||
#include <boost/python/return_value_policy.hpp>
|
||||
|
||||
// classes to wrap
|
||||
struct Bar { int x; }
|
||||
|
||||
struct Foo {
|
||||
Foo(int x) : { b.x = x; }
|
||||
Bar const& get_bar() const { return b; }
|
||||
private:
|
||||
Bar b;
|
||||
};
|
||||
|
||||
// Wrapper code
|
||||
using namespace boost::python;
|
||||
BOOST_PYTHON_MODULE(my_module)
|
||||
{
|
||||
class_<Bar>("Bar");
|
||||
|
||||
class_<Foo>("Foo", init<int>())
|
||||
.def("get_bar", &Foo::get_bar
|
||||
, return_value_policy<copy_const_reference>())
|
||||
;
|
||||
}
|
||||
</pre>
|
||||
|
||||
<h3>Python Code</h3>
|
||||
<pre>
|
||||
>>> from my_module import *
|
||||
>>> f = Foo(3) # create a Foo object
|
||||
>>> b = f.get_bar() # make a copy of the internal Bar object
|
||||
</pre>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,147 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python -
|
||||
<boost/python/copy_non_const_reference.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header
|
||||
<boost/python/copy_non_const_reference.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#copy_non_const_reference-spec">Class
|
||||
<code>copy_non_const_reference</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#copy_non_const_reference-spec-synopsis">Class
|
||||
<code>copy_non_const_reference</code> synopsis</a></dt>
|
||||
|
||||
<dt><a href=
|
||||
"#copy_non_const_reference-spec-metafunctions">Class
|
||||
<code>copy_non_const_reference</code> metafunctions</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="copy_non_const_reference-spec"></a>Class
|
||||
<code>copy_non_const_reference</code></h3>
|
||||
|
||||
<p><code>copy_non_const_reference</code> is a model of <a href=
|
||||
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a>
|
||||
which can be used to wrap C++ functions returning a
|
||||
reference-to-non-const type such that the referenced value is copied into
|
||||
a new Python object.</p>
|
||||
|
||||
<h4><a name="copy_non_const_reference-spec-synopsis"></a>Class
|
||||
<code>copy_non_const_reference</code> synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
struct copy_non_const_reference
|
||||
{
|
||||
template <class T> struct apply;
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="copy_non_const_reference-spec-metafunctions"></a>Class
|
||||
<code>copy_non_const_reference</code> metafunctions</h4>
|
||||
<pre>
|
||||
template <class T> struct apply
|
||||
</pre>
|
||||
|
||||
<dl class="metafunction-semantics">
|
||||
<dt><b>Requires:</b> <code>T</code> is <code>U&</code> for some
|
||||
non-const <code>U</code>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>typedef <a href=
|
||||
"to_python_value.html#to_python_value-spec">to_python_value</a><T>
|
||||
type;</code></dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
|
||||
<p>C++ code:</p>
|
||||
<pre>
|
||||
#include <boost/python/module.hpp>
|
||||
#include <boost/python/class.hpp>
|
||||
#include <boost/python/copy_non_const_reference.hpp>
|
||||
#include <boost/python/return_value_policy.hpp>
|
||||
|
||||
// classes to wrap
|
||||
struct Bar { int x; }
|
||||
|
||||
struct Foo {
|
||||
Foo(int x) : { b.x = x; }
|
||||
Bar& get_bar() { return b; }
|
||||
private:
|
||||
Bar b;
|
||||
};
|
||||
|
||||
// Wrapper code
|
||||
using namespace boost::python;
|
||||
BOOST_PYTHON_MODULE(my_module)
|
||||
{
|
||||
class_<Bar>("Bar");
|
||||
|
||||
class_<Foo>("Foo", init<int>())
|
||||
.def("get_bar", &Foo::get_bar
|
||||
, return_value_policy<copy_non_const_reference>())
|
||||
;
|
||||
}
|
||||
</pre>
|
||||
Python Code:
|
||||
<pre>
|
||||
>>> from my_module import *
|
||||
>>> f = Foo(3) # create a Foo object
|
||||
>>> b = f.get_bar() # make a copy of the internal Bar object
|
||||
</pre>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,227 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/data_members.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header
|
||||
<boost/python/data_members.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#functions">Functions</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#make_getter-spec">make_getter</a></dt>
|
||||
|
||||
<dt><a href="#make_setter-spec">make_setter</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><code><a href="#make_getter-spec">make_getter</a>()</code> and
|
||||
<code><a href="#make_setter-spec">make_setter</a>()</code> are the
|
||||
functions used internally by <code>class_<>::<a href=
|
||||
"class.html#class_-spec-modifiers">def_readonly</a></code> and
|
||||
<code>class_<>::<a href=
|
||||
"class.html#class_-spec-modifiers">def_readwrite</a></code> to produce
|
||||
Python callable objects which wrap C++ data members.</p>
|
||||
|
||||
<h2><a name="functions"></a>Functions</h2>
|
||||
<pre>
|
||||
<a name="make_getter-spec">template <class C, class D></a>
|
||||
<a href="object.html#object-spec">object</a> make_getter(D C::*pm);
|
||||
|
||||
template <class C, class D, class Policies>
|
||||
<a href=
|
||||
"object.html#object-spec">object</a> make_getter(D C::*pm, Policies const& policies);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
|
||||
"CallPolicies.html">CallPolicies</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Creates a Python callable object which accepts a
|
||||
single argument that can be converted <code>from_python</code> to
|
||||
<code>C*</code>, and returns the corresponding member <code>D</code>
|
||||
member of the <code>C</code> object, converted <code>to_python</code>.
|
||||
If <code>policies</code> is supplied, it will be applied to the
|
||||
function as described <a href="CallPolicies.html">here</a>. Otherwise,
|
||||
the library attempts to determine whether <code>D</code> is a
|
||||
user-defined class type, and if so uses <code><a href=
|
||||
"return_internal_reference.html#return_internal_reference-spec">return_internal_reference</a><></code></dt>
|
||||
|
||||
<dt>for <code>Policies</code>. Note that this test may inappropriately
|
||||
choose <code>return_internal_reference<></code> in some cases
|
||||
when <code>D</code> is a smart pointer type. This is a known
|
||||
defect.</dt>
|
||||
|
||||
<dt><b>Returns:</b> An instance of <a href=
|
||||
"object.html#object-spec">object</a> which holds the new Python
|
||||
callable object.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
template <class D>
|
||||
<a href="object.html#object-spec">object</a> make_getter(D const& d);
|
||||
template <class D, class Policies>
|
||||
<a href=
|
||||
"object.html#object-spec">object</a> make_getter(D const& d, Policies const& policies);
|
||||
|
||||
template <class D>
|
||||
<a href="object.html#object-spec">object</a> make_getter(D const* p);
|
||||
template <class D, class Policies>
|
||||
<a href=
|
||||
"object.html#object-spec">object</a> make_getter(D const* p, Policies const& policies);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
|
||||
"CallPolicies.html">CallPolicies</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Creates a Python callable object which accepts no
|
||||
arguments and returns <code>d</code> or <code>*p</code>, converted
|
||||
<code>to_python</code> on demand. If <code>policies</code> is supplied,
|
||||
it will be applied to the function as described <a href=
|
||||
"CallPolicies.html">here</a>. Otherwise, the library attempts to
|
||||
determine whether <code>D</code> is a user-defined class type, and if
|
||||
so uses <code><a href=
|
||||
"reference_existing_object.html#reference_existing_object-spec">reference_existing_object</a></code></dt>
|
||||
|
||||
<dt>for <code>Policies</code>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> An instance of <a href=
|
||||
"object.html#object-spec">object</a> which holds the new Python
|
||||
callable object.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
<a name="make_setter-spec">template <class C, class D></a>
|
||||
<a href="object.html#object-spec">object</a> make_setter(D C::*pm);
|
||||
|
||||
template <class C, class D, class Policies>
|
||||
<a href=
|
||||
"object.html#object-spec">object</a> make_setter(D C::*pm, Policies const& policies);
|
||||
</pre>
|
||||
|
||||
<dl class="function*-semantics">
|
||||
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
|
||||
"CallPolicies.html">CallPolicies</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Creates a Python callable object which, when called
|
||||
from Python, expects two arguments which can be converted
|
||||
<code>from_python</code> to <code>C*</code> and
|
||||
<code>D const&</code>, respectively, and sets the
|
||||
corresponding <code>D</code> member of the <code>C</code> object. If
|
||||
<code>policies</code> is supplied, it will be applied to the function
|
||||
as described <a href="CallPolicies.html">here</a>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> An instance of <a href=
|
||||
"object.html#object-spec">object</a> which holds the new Python
|
||||
callable object.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
template <class D>
|
||||
<a href="object.html#object-spec">object</a> make_setter(D& d);
|
||||
template <class D, class Policies>
|
||||
<a href=
|
||||
"object.html#object-spec">object</a> make_setter(D& d, Policies const& policies);
|
||||
|
||||
template <class D>
|
||||
<a href="object.html#object-spec">object</a> make_setter(D* p);
|
||||
template <class D, class Policies>
|
||||
<a href=
|
||||
"object.html#object-spec">object</a> make_setter(D* p, Policies const& policies);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>Policies</code> is a model of <a href=
|
||||
"CallPolicies.html">CallPolicies</a>.</dt>
|
||||
|
||||
<dt><b>Effects:</b> Creates a Python callable object which accepts one
|
||||
argument, which is converted from Python to <code>D const&</code>
|
||||
and written into <code>d</code> or <code>*p</code>, respectively. If
|
||||
<code>policies</code> is supplied, it will be applied to the function
|
||||
as described <a href="CallPolicies.html">here</a>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> An instance of <a href=
|
||||
"object.html#object-spec">object</a> which holds the new Python
|
||||
callable object.</dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
|
||||
<p>The code below uses make_getter and make_setter to expose a data
|
||||
member as functions:</p>
|
||||
<pre>
|
||||
#include <boost/python/data_members.hpp>
|
||||
#include <boost/python/module.hpp>
|
||||
#include <boost/python/class.hpp>
|
||||
|
||||
struct X
|
||||
{
|
||||
X(int x) : y(x) {}
|
||||
int y;
|
||||
};
|
||||
|
||||
using namespace boost::python;
|
||||
|
||||
BOOST_PYTHON_MODULE_INIT(data_members_example)
|
||||
{
|
||||
class_<X>("X", init<int>())
|
||||
.def("get", make_getter(&X::y))
|
||||
.def("set", make_setter(&X::y))
|
||||
;
|
||||
}
|
||||
</pre>
|
||||
It can be used this way in Python:
|
||||
<pre>
|
||||
>>> from data_members_example import *
|
||||
>>> x = X(1)
|
||||
>>> x.get()
|
||||
1
|
||||
>>> x.set(2)
|
||||
>>> x.get()
|
||||
2
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
5 August, 2003 <!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
189
doc/v2/def.html
189
doc/v2/def.html
@@ -1,189 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Cygwin (vers 1st April 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/def.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/def.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#functions">Functions</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#def-spec">def</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><code><a href="#def-spec">def</a>()</code> is the function which can
|
||||
be used to expose C++ functions and callable objects as Python functions
|
||||
in the current <code><a href="scope.html">scope</a></code>.</p>
|
||||
|
||||
<h2><a name="functions"></a>Functions</h2>
|
||||
<a name="def-spec"></a>def
|
||||
<pre>
|
||||
template <class F>
|
||||
void def(char const* name, F f);
|
||||
|
||||
template <class Fn, class A1>
|
||||
void def(char const* name, Fn fn, A1 const&);
|
||||
|
||||
template <class Fn, class A1, class A2>
|
||||
void def(char const* name, Fn fn, A1 const&, A2 const&);
|
||||
|
||||
template <class Fn, class A1, class A2, class A3>
|
||||
void def(char const* name, Fn fn, A1 const&, A2 const&, A3 const&);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.</dt>
|
||||
|
||||
<dd>
|
||||
<ul>
|
||||
<li>If <code>Fn</code> is [derived from] <code><a href=
|
||||
"object.html#object-spec">object</a></code>, it will be added to
|
||||
the current scope as a single overload. To be useful,
|
||||
<code>fn</code> should be <a href=
|
||||
"http://www.python.org/doc/current/lib/built-in-funcs.html#l2h-6">callable</a>.</li>
|
||||
|
||||
<li>
|
||||
If <code>a1</code> is the result of an <a href=
|
||||
"overloads.html#overload-dispatch-expression"><em>overload-dispatch-expression</em></a>,
|
||||
only the second form is allowed and fn must be a pointer to
|
||||
function or pointer to member function whose <a href=
|
||||
"definitions.html#arity">arity</a> is the same as A1's <a href=
|
||||
"overloads.html#overload-dispatch-expression"><em>maximum
|
||||
arity</em></a>.
|
||||
|
||||
<dl>
|
||||
<dt><b>Effects:</b> For each prefix <em>P</em> of
|
||||
<code>Fn</code>'s sequence of argument types, beginning with
|
||||
the one whose length is <code>A1</code>'s <a href=
|
||||
"overloads.html#overload-dispatch-expression"><em>minimum
|
||||
arity</em></a>, adds a
|
||||
<code><em>name</em>(</code>...<code>)</code> function overload
|
||||
to the <a href="scope.html">current scope</a>. Each overload
|
||||
generated invokes <code>a1</code>'s call-expression with
|
||||
<em>P</em>, using a copy of <code>a1</code>'s <a href=
|
||||
"CallPolicies.html">call policies</a>. If the longest valid
|
||||
prefix of <code>A1</code> contains <em>N</em> types and
|
||||
<code>a1</code> holds <em>M</em> keywords, an initial sequence
|
||||
of the keywords are used for all but the first
|
||||
<em>N</em> - <em>M</em> arguments of each
|
||||
overload.<br>
|
||||
</dt>
|
||||
</dl>
|
||||
</li>
|
||||
|
||||
<li>Otherwise, fn must be a non-null function or member function
|
||||
pointer, and a single function overload built around fn is added to
|
||||
the <a href="scope.html">current scope</a>. If any of
|
||||
<code>a1</code>-<code>a3</code> are supplied, they may be selected
|
||||
in any order from the table below.</li>
|
||||
</ul>
|
||||
|
||||
<table border="1" summary="def() optional arguments">
|
||||
<tr>
|
||||
<th>Memnonic Name</th>
|
||||
|
||||
<th>Requirements/Type properties</th>
|
||||
|
||||
<th>Effects</th>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>docstring</td>
|
||||
|
||||
<td>Any <a href="definitions.html#ntbs">ntbs</a>.</td>
|
||||
|
||||
<td>Value will be bound to the <code>__doc__</code> attribute of
|
||||
the resulting method overload.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>policies</td>
|
||||
|
||||
<td>A model of <a href="CallPolicies.html">CallPolicies</a></td>
|
||||
|
||||
<td>A copy will be used as the call policies of the resulting
|
||||
method overload.</td>
|
||||
</tr>
|
||||
|
||||
<tr>
|
||||
<td>keywords</td>
|
||||
|
||||
<td>The result of a <a href=
|
||||
"args.html#keyword-expression"><em>keyword-expression</em></a>
|
||||
specifying no more arguments than the <a href=
|
||||
"definitions.html#arity">arity</a> of <code>fn</code>.</td>
|
||||
|
||||
<td>A copy will be used as the call policies of the resulting
|
||||
method overload.</td>
|
||||
</tr>
|
||||
</table>
|
||||
</dd>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
<pre>
|
||||
#include <boost/python/def.hpp>
|
||||
#include <boost/python/module.hpp>
|
||||
#include <boost/python/args.hpp>
|
||||
|
||||
using namespace boost::python;
|
||||
|
||||
char const* foo(int x, int y) { return "foo"; }
|
||||
|
||||
BOOST_PYTHON_MODULE(def_test)
|
||||
{
|
||||
def("foo", foo, args("x", "y"), "foo's docstring");
|
||||
}
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
7 March, 2003
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,135 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
<meta name="generator" content="Microsoft FrontPage 5.0">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/def_visitor.hpp></title>
|
||||
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html"><font size="7">Boost.Python</font></a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/def_visitor.hpp></h2>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a>
|
||||
<dt><a href="#classes">Classes</a>
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#def_visitor-spec">Class <code>def_visitor</code></a>
|
||||
<dd> <a href="#def_visitor-synopsis">Class <code>def_visitor</code>
|
||||
synopsis</a></dd>
|
||||
<dd> <a href="#def_visitor-requirements">Class <code>def_visitor</code>
|
||||
requirements</a></dd>
|
||||
</dl>
|
||||
<dt><a href="#examples">Example</a>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
|
||||
<p><code><boost/python/def_visitor.hpp></code> provides a generic visitation
|
||||
interface through which the <a href="class.html">class_</a> <b>def</b> member
|
||||
functionality can be extended non-intrusively to avoid cluttering the <a href="class.html">class_</a>
|
||||
interface. It declares the <code>def_visitor<T> </code>class template,
|
||||
which is parameterized on the derived type <tt>DerivedVisitor</tt>, which provides
|
||||
the actual <b>def</b> functionality through its <b>visit</b> member functions.
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="def_visitor-spec"></a>Class template <code>def_visitor<DerivedVisitor></code></h3>
|
||||
|
||||
|
||||
<p>The class def_visitor is a base class paramaterized by its derived class. The
|
||||
def_visitor class is a protocol class. Its derived class, DerivedVisitor, is
|
||||
expected to have a member function visit. The def_visitor class is never instantiated
|
||||
directly. Instead, an instance of its subclass, DerivedVisitor, is passed
|
||||
on as an argument to the <a href="class.html">class_</a> def member function.
|
||||
<h4>
|
||||
<a name="def_visitor-synopsis" id="def_visitor-synopsis"></a>Class <code>def_visitor </code>synopsis</h4>
|
||||
<pre>namespace boost { namespace python {
|
||||
|
||||
template <class DerivedVisitor>
|
||||
class def_visitor {};
|
||||
}</pre>
|
||||
<h3><a name="def_visitor-requirements"></a><code>def_visitor </code>requirements</h3>
|
||||
|
||||
|
||||
<p>The <span class="pre">client supplied class </span><span class="pre"></span><tt class="literal"><span class="pre">DerivedVisitor</span></tt>
|
||||
template parameter is expected to:
|
||||
<ul>
|
||||
<li>be privately derived from def_visitor</li>
|
||||
<li>grant friend access to class def_visitor_access</li>
|
||||
<li>define either or both visit member functions listed in the table below:</li>
|
||||
</ul>
|
||||
|
||||
|
||||
<table border class="table">
|
||||
<tr>
|
||||
<td width="181" nowrap><b>Expression</b></td>
|
||||
<td width="85"><b>Return Type</b></td>
|
||||
<td width="330"><b>Requirements</b></td>
|
||||
<td width="259"><b>Effects</b></td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td nowrap>visitor.visit(cls)</td>
|
||||
<td>void</td>
|
||||
<td>cls is an instance of a <a href="class.html">class_</a> being wrapped
|
||||
to Python. visitor is a def_visitor derived class.</td>
|
||||
<td>A call to cls.def(visitor) forwards to this member function.</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td nowrap>visitor.visit(cls, name, options)</td>
|
||||
<td>void</td>
|
||||
<td>cls is a class_ instance, name is a C string. visitor is a def_visitor
|
||||
derived class. options is a context specific optional argument.</td>
|
||||
<td>A call to cls.def(name, visitor) or cls.def(name, visitor, options) forwards
|
||||
to this member function. </td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
|
||||
|
||||
<pre>class X {/*...*/};<br>
|
||||
class my_def_visitor : boost::python::def_visitor<my_def_visitor>
|
||||
{
|
||||
friend class def_visitor_access;
|
||||
|
||||
template <class classT>
|
||||
void visit(classT& c) const
|
||||
{
|
||||
c
|
||||
.def("foo", &my_def_visitor::foo)
|
||||
.def("bar", &my_def_visitor::bar)
|
||||
;
|
||||
}
|
||||
|
||||
static void foo(X& self);
|
||||
static void bar(X& self);
|
||||
};
|
||||
|
||||
BOOST_PYTHON_MODULE(my_ext)
|
||||
{
|
||||
class_<X>("X")
|
||||
.def(my_def_visitor())
|
||||
;
|
||||
}
|
||||
</pre>
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->27 August, 2003<!--webbot bot="Timestamp" endspan i-checksum="34484" -->
|
||||
</p>
|
||||
|
||||
|
||||
<p><i>© Copyright Joel de Guzman 2003. All Rights Reserved.</i>
|
||||
@@ -1,170 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
<meta name="generator" content="HTML Tidy, see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python -
|
||||
<boost/python/default_call_policies.hpp></title>
|
||||
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277" alt=
|
||||
"C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header
|
||||
<boost/python/default_call_policies.hpp></h2>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#classes">Classes</a>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#default_call_policies-spec">Class
|
||||
<code>default_call_policies</code></a>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#default_call_policies-spec-synopsis">Class
|
||||
<code>default_call_policies</code> synopsis</a>
|
||||
|
||||
<dt><a href="#default_call_policies-spec-statics">Class
|
||||
<code>default_call_policies</code> static functions</a>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#default_result_converter-spec">Class
|
||||
<code>default_result_converter</code></a>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#default_result_converter-spec-synopsis">Class
|
||||
<code>default_result_converter</code> synopsis</a>
|
||||
|
||||
<dt><a href="#default_result_converter-spec-metafunctions">Class
|
||||
<code>default_result_converter</code> metafunctions</a>
|
||||
</dl>
|
||||
</dl>
|
||||
|
||||
<dt><a href="#examples">Example</a>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="default_call_policies-spec"></a>Class
|
||||
<code>default_call_policies</code></h3>
|
||||
|
||||
<p><code>default_call_policies</code> is a model of <a href=
|
||||
"CallPolicies.html">CallPolicies</a> with no <code>precall</code> or
|
||||
<code>postcall</code> behavior and a <code>result_converter</code> which
|
||||
handles by-value returns. Wrapped C++ functions and member functions use
|
||||
<code>default_call_policies</code> unless otherwise specified. You may find
|
||||
it convenient to derive new models of <a href=
|
||||
"CallPolicies.html">CallPolicies</a> from
|
||||
<code>default_call_policies</code>.
|
||||
|
||||
<h4><a name="default_call_policies-spec-synopsis"></a>Class
|
||||
<code>default_call_policies</code> synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
struct default_call_policies
|
||||
{
|
||||
static bool precall(PyObject*);
|
||||
static PyObject* postcall(PyObject*, PyObject* result);
|
||||
typedef <a href=
|
||||
"#default_result_converter-spec">default_result_converter</a> result_converter;
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="default_call_policies-spec-statics"></a>Class
|
||||
<code>default_call_policies</code> static functions</h4>
|
||||
<pre>
|
||||
bool precall(PyObject*);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Returns:</b> <code>true</code>
|
||||
|
||||
<dt><b>Throws:</b> nothing
|
||||
</dl>
|
||||
<pre>
|
||||
PyObject* postcall(PyObject*, PyObject* result);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Returns:</b> <code>result</code>
|
||||
|
||||
<dt><b>Throws:</b> nothing
|
||||
</dl>
|
||||
|
||||
<h3><a name="default_result_converter-spec"></a>Class
|
||||
<code>default_result_converter</code></h3>
|
||||
|
||||
<p><code>default_result_converter</code> is a model of <a href=
|
||||
"ResultConverter.html#ResultConverterGenerator-concept">ResultConverterGenerator</a> which can be
|
||||
used to wrap C++ functions returning non-pointer types, <code>char
|
||||
const*</code>, and <code>PyObject*</code>, by-value.
|
||||
|
||||
<h4><a name="default_result_converter-spec-synopsis"></a>Class
|
||||
<code>default_result_converter</code> synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
struct default_result_converter
|
||||
{
|
||||
template <class T> struct apply;
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="default_result_converter-spec-metafunctions"></a>Class
|
||||
<code>default_result_converter</code> metafunctions</h4>
|
||||
<pre>
|
||||
template <class T> struct apply
|
||||
</pre>
|
||||
|
||||
<dl class="metafunction-semantics">
|
||||
<dt><b>Requires:</b> <code>T</code> is not a reference type. If
|
||||
<code>T</code> is a pointer type, <code>T</code> is <code>const
|
||||
char*</code> or <code>PyObject*</code>.
|
||||
|
||||
<dt><b>Returns:</b> <code>typedef <a href=
|
||||
"to_python_value.html#to_python_value-spec">to_python_value</a><T
|
||||
const&> type;</code>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
|
||||
<p>This example comes from the Boost.Python implementation itself. Because
|
||||
the <a href=
|
||||
"return_value_policy.html#return_value_policy-spec">return_value_policy</a>
|
||||
class template does not implement <code>precall</code> or
|
||||
<code>postcall</code> behavior, its default base class is
|
||||
<code>default_call_policies</code>:
|
||||
<pre>
|
||||
template <class Handler, class Base = default_call_policies>
|
||||
struct return_value_policy : Base
|
||||
{
|
||||
typedef Handler result_converter;
|
||||
};
|
||||
</pre>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
|
||||
|
||||
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
|
||||
Abrahams</a> 2002. All Rights Reserved.</i>
|
||||
|
||||
@@ -1,100 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - Definitions</title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Definitions</h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<dl class="definitions">
|
||||
<dt><b><a name="arity">arity</a>:</b> The number of arguments accepted
|
||||
by a function or member function. Unless otherwise specified, the
|
||||
hidden "<code>this</code>" argument to member functions is not counted
|
||||
when specifying arity</dt>
|
||||
|
||||
<dd><br>
|
||||
</dd>
|
||||
|
||||
<dt><b><a name="ntbs">ntbs</a>:</b> Null-Terminated Byte String, or
|
||||
`C'-string. C++ string literals are <strong>ntbs</strong>es. An
|
||||
<strong>ntbs</strong> must never be null.</dt>
|
||||
|
||||
<dd><br>
|
||||
</dd>
|
||||
|
||||
<dt><b><a name="raise">raise</a>:</b> Exceptions in Python are
|
||||
"raised", not "thrown", as they are in C++. When this documentation
|
||||
says that some Python exception is "raised" in the context of C++ code,
|
||||
it means that the corresponding Python exception is set via the <a
|
||||
href=
|
||||
"http://www.python.org/doc/current/api/exceptionHandling.html">Python/'C'
|
||||
API</a>, and <code><a href=
|
||||
"errors.html#throw_error_already_set-spec">throw_error_already_set</a>()</code>
|
||||
is called.</dt>
|
||||
|
||||
<dd><br>
|
||||
</dd>
|
||||
|
||||
<dt><b><a name="POD">POD</a>:</b> A technical term from the C++
|
||||
standard. Short for "Plain Ol'Data": A POD-struct is an aggregate class
|
||||
that has no non-static data members of type pointer to member,
|
||||
non-POD-struct, non-POD-union (or array of such types) or reference,
|
||||
and has no user-defined copy assign- ment operator and no user-defined
|
||||
destructor. Similarly, a POD-union is an aggregate union that has no
|
||||
non-static data members of type pointer to member, non-POD-struct,
|
||||
non-POD-union (or array of such types) or reference, and has no
|
||||
user-defined copy assignment operator and no user-defined destructor. A
|
||||
POD class is a class that is either a POD-struct or a POD-union. An
|
||||
aggregate is an array or a class (clause 9) with no user-declared
|
||||
constructors (12.1), no private or protected non-static data members
|
||||
(clause 11), no base classes (clause 10), and no virtual functions
|
||||
(10.3).</dt>
|
||||
|
||||
<dd><br>
|
||||
</dd>
|
||||
|
||||
<dt><b><a name="ODR">ODR</a>:</b> The "One Definition
|
||||
Rule", which says that any entity in a C++ program must have the same definition in all translation units (object files) which make up a program.
|
||||
</dt>
|
||||
|
||||
<dd><br>
|
||||
</dd>
|
||||
|
||||
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
150
doc/v2/dict.html
150
doc/v2/dict.html
@@ -1,150 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/dict.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/dict.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#dict-spec">Class <code>dict</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#dict-spec-synopsis">Class <code>dict</code>
|
||||
synopsis</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>Exposes a <a href=
|
||||
"ObjectWrapper.html#TypeWrapper-concept">TypeWrapper</a> for the Python
|
||||
<a href=
|
||||
"http://www.python.org/dev/doc/devel/lib/typesmapping.html">dict</a>
|
||||
type.</p>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="dict-spec"></a>Class <code>dict</code></h3>
|
||||
|
||||
<p>Exposes the <a href=
|
||||
"http://www.python.org/dev/doc/devel/lib/typesmapping.html">mapping
|
||||
protocol</a> of Python's built-in <code>dict</code> type. The semantics
|
||||
of the constructors and member functions defined below can be fully
|
||||
understood by reading the <a href=
|
||||
"ObjectWrapper.html#TypeWrapper-concept">TypeWrapper</a> concept
|
||||
definition. Since <code>dict</code> is publicly derived from <code><a
|
||||
href="object.html#object-spec">object</a></code>, the public object
|
||||
interface applies to <code>dict</code> instances as well.</p>
|
||||
|
||||
<h4><a name="dict-spec-synopsis"></a>Class <code>dict</code>
|
||||
synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
class dict : public object
|
||||
{
|
||||
dict();
|
||||
|
||||
template< class T >
|
||||
dict(T const & data);
|
||||
|
||||
// modifiers
|
||||
void clear();
|
||||
dict copy();
|
||||
|
||||
template <class T1, class T2>
|
||||
tuple popitem();
|
||||
|
||||
template <class T>
|
||||
object setdefault(T const &k);
|
||||
|
||||
template <class T1, class T2>
|
||||
object setdefault(T1 const & k, T2 const & d);
|
||||
|
||||
void update(object_cref E);
|
||||
|
||||
template< class T >
|
||||
void update(T const & E);
|
||||
|
||||
// observers
|
||||
list values() const;
|
||||
|
||||
object get(object_cref k) const;
|
||||
|
||||
template<class T>
|
||||
object get(T const & k) const;
|
||||
|
||||
object get(object_cref k, object_cref d) const;
|
||||
object get(T1 const & k, T2 const & d) const;
|
||||
|
||||
bool has_key(object_cref k) const;
|
||||
|
||||
template< class T >
|
||||
bool has_key(T const & k) const;
|
||||
|
||||
list items() const;
|
||||
object iteritems() const;
|
||||
object iterkeys() const;
|
||||
object itervalues() const;
|
||||
list keys() const;
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
<pre>
|
||||
using namespace boost::python;
|
||||
dict swap_object_dict(object target, dict d)
|
||||
{
|
||||
dict result = extract<dict>(target.attr("__dict__"));
|
||||
target.attr("__dict__") = d;
|
||||
return result;
|
||||
}
|
||||
</pre>
|
||||
|
||||
<p>Revised 30 September, 2002</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
232
doc/v2/enum.html
232
doc/v2/enum.html
@@ -1,232 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/enum.hpp></title>
|
||||
</head>
|
||||
|
||||
<body link="#0000ff" vlink="#800080">
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/enum.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#enum_-spec">Class template
|
||||
<code>enum_</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#enum_-spec-synopsis">Class template <code>enum_</code>
|
||||
synopsis</a></dt>
|
||||
|
||||
<dt><a href="#enum_-spec-ctors">Class template <code>enum_</code>
|
||||
constructors</a></dt>
|
||||
|
||||
<dt><a href="#enum_-spec-modifiers">Class template <code>enum_</code>
|
||||
modifier functions</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><code><boost/python/enum.hpp></code> defines the
|
||||
interface through which users expose their C++ enumeration types
|
||||
to Python. It declares the
|
||||
<code>enum_</code> class template, which is parameterized on the
|
||||
enumeration type being exposed. </p>
|
||||
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="enum_-spec"></a>Class template
|
||||
<code>enum_<T></code></h3>
|
||||
|
||||
<p>Creates a Python class derived from Python's <code>int</code>
|
||||
type which is associated with the C++ type passed as its first
|
||||
parameter.
|
||||
|
||||
<h4><a name="enum_-spec-synopsis"></a>Class template <code>enum_</code>
|
||||
synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
template <class T>
|
||||
class enum_ : public <a href="object.html#object-spec">object</a>
|
||||
{
|
||||
enum_(char const* name);
|
||||
enum_<T>& value(char const* name, T);
|
||||
enum_<T>& export_values();
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="enum_-spec-ctors"></a>Class template <code>enum_</code>
|
||||
constructors</h4>
|
||||
<pre>
|
||||
enum_(char const* name);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.
|
||||
|
||||
<dt><b>Effects:</b> Constructs an <code>enum_</code> object
|
||||
holding a Python extension type derived from <code>int</code>
|
||||
which is named <code>name</code>. The
|
||||
<code>name</code>d attribute of the <a href=
|
||||
"scope.html#introduction">current scope</a> is bound to the new
|
||||
extension type.</dt>
|
||||
</dl>
|
||||
|
||||
<h4><a name="enum_-spec-modifiers"></a>Class template
|
||||
<code>enum_</code> modifier functions</h4>
|
||||
<pre>
|
||||
inline enum_<T>& value(char const* name, T x);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> <code>name</code> is an <a href=
|
||||
"definitions.html#ntbs">ntbs</a> which conforms to Python's <a
|
||||
href=
|
||||
"http://www.python.org/doc/current/ref/identifiers.html">identifier
|
||||
naming rules</a>.
|
||||
|
||||
<dt><b>Effects:</b> adds an instance of the wrapped enumeration
|
||||
type with value <code>x</code> to the type's dictionary as the
|
||||
<code>name</code>d attribute</dt>.
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
</dl>
|
||||
|
||||
<pre>
|
||||
inline enum_<T>& export_values();
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
|
||||
<dt><b>Effects:</b> sets attributes in the current <a
|
||||
href="scope.html#scope-spec"><code>scope</code></a> with the
|
||||
same names and values as all enumeration values exposed so far
|
||||
by calling <code>value()</code></dt>.
|
||||
|
||||
<dt><b>Returns:</b> <code>*this</code></dt>
|
||||
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example(s)</h2>
|
||||
|
||||
<p>C++ module definition
|
||||
<pre>
|
||||
#include <boost/python/enum.hpp>
|
||||
#include <boost/python/def.hpp>
|
||||
#include <boost/python/module.hpp>
|
||||
|
||||
using namespace boost::python;
|
||||
|
||||
enum color { red = 1, green = 2, blue = 4 };
|
||||
|
||||
color identity_(color x) { return x; }
|
||||
|
||||
BOOST_PYTHON_MODULE(enums)
|
||||
{
|
||||
enum_<color>("color")
|
||||
.value("red", red)
|
||||
.value("green", green)
|
||||
.export_values()
|
||||
.value("blue", blue)
|
||||
;
|
||||
|
||||
def("identity", identity_);
|
||||
}
|
||||
</pre>
|
||||
<p>Interactive Python:
|
||||
<pre>
|
||||
>>> from enums import *
|
||||
|
||||
>>> identity(red)
|
||||
enums.color.red
|
||||
|
||||
>>> identity(color.red)
|
||||
enums.color.red
|
||||
|
||||
>>> identity(green)
|
||||
enums.color.green
|
||||
|
||||
>>> identity(color.green)
|
||||
enums.color.green
|
||||
|
||||
>>> identity(blue)
|
||||
Traceback (most recent call last):
|
||||
File "<stdin>", line 1, in ?
|
||||
NameError: name blue' is not defined
|
||||
|
||||
>>> identity(color.blue)
|
||||
enums.color.blue
|
||||
|
||||
>>> identity(color(1))
|
||||
enums.color.red
|
||||
|
||||
>>> identity(color(2))
|
||||
enums.color.green
|
||||
|
||||
>>> identity(color(3))
|
||||
enums.color(3)
|
||||
|
||||
>>> identity(color(4))
|
||||
enums.color.blue
|
||||
|
||||
>>> identity(1)
|
||||
Traceback (most recent call last):
|
||||
File "<stdin>", line 1, in ?
|
||||
TypeError: bad argument type for built-in operation
|
||||
</pre>
|
||||
<hr>
|
||||
|
||||
Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 December, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,287 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/errors.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/errors.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#error_already_set-spec">Class
|
||||
<code>error_already_set</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#error_already_set-spec-synopsis">Class
|
||||
<code>error_already_set</code> synopsis</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#functions">Functions</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#handle_exception-spec">handle_exception</a></dt>
|
||||
|
||||
<dt><a href="#expect_non_null-spec">expect_non_null</a></dt>
|
||||
|
||||
<dt><a href=
|
||||
"#throw_error_already_set-spec">throw_error_already_set</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Examples</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p><code><boost/python/errors.hpp></code> provides types and
|
||||
functions for managing and translating between Python and C++ exceptions.
|
||||
This is relatively low-level functionality that is mostly used internally
|
||||
by Boost.Python. Users should seldom need it.</p>
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="error_already_set-spec"></a>Class
|
||||
<code>error_already_set</code></h3>
|
||||
|
||||
<p><code>error_already_set</code> is an exception type which can be
|
||||
thrown to indicate that a Python error has occurred. If thrown, the
|
||||
precondition is that <a href=
|
||||
"http://www.python.org/doc/2.2/api/exceptionHandling.html#l2h-71">PyErr_Occurred()</a>
|
||||
returns a value convertible to <code>true</code>. Portable code shouldn't
|
||||
throw this exception type directly, but should instead use <code><a href=
|
||||
"#throw_error_already_set-spec">throw_error_already_set</a>()</code>,
|
||||
below.</p>
|
||||
|
||||
<h4><a name="error_already_set-spec-synopsis"></a>Class error_already_set
|
||||
synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
class error_already_set {};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h2><a name="functions"></a>Functions</h2>
|
||||
<pre>
|
||||
<a name=
|
||||
"handle_exception-spec">template <class T> bool handle_exception</a>(T f) throw();
|
||||
|
||||
void handle_exception() throw();
|
||||
</pre>
|
||||
|
||||
<dl class="handle_exception-semantics">
|
||||
<dt><b>Requires:</b> The first form requires that the expression
|
||||
<code><a href=
|
||||
"../../../function/doc/reference.html#functionN">function0</a><void>(f)</code>
|
||||
is valid. The second form requires that a C++ exception is currently
|
||||
being handled (see section 15.1 in the C++ standard).</dt>
|
||||
|
||||
<dt><b>Effects:</b> The first form calls <code>f()</code> inside a
|
||||
<code>try</code> block which first attempts to use all registered <a
|
||||
href="exception_translator.html">exception translators</a>. If none of
|
||||
those translates the exception, the <code>catch</code> clauses then set
|
||||
an appropriate Python exception for the C++ exception caught, returning
|
||||
<code>true</code> if an exception was thrown, <code>false</code>
|
||||
otherwise. The second form passes a function which rethrows the
|
||||
exception currently being handled to the first form.</dt>
|
||||
|
||||
<dt><b>Postconditions:</b> No exception is being handled</dt>
|
||||
|
||||
<dt><b>Throws:</b> nothing</dt>
|
||||
|
||||
<dt><b>Rationale:</b> At inter-language boundaries it is important to
|
||||
ensure that no C++ exceptions escape, since the calling language
|
||||
usually doesn't have the equipment neccessary to properly unwind the
|
||||
stack. Use <code>handle_exception</code> to manage exception
|
||||
translation whenever your C++ code is called directly from the Python
|
||||
API. This is done for you automatically by the usual function wrapping
|
||||
facilities: <code><a href=
|
||||
"make_function.html#make_function-spec">make_function</a>()</code>,
|
||||
<code><a href=
|
||||
"make_function.html#make_constructor-spec">make_constructor</a>()</code>,
|
||||
<code><a href="def.html#def-spec">def</a>()</code> and <code><a href=
|
||||
"class.html#def-spec">class_::def</a>()</code>. The second form can be
|
||||
more convenient to use (see the <a href="#examples">example</a> below),
|
||||
but various compilers have problems when exceptions are rethrown from
|
||||
within an enclosing <code>try</code> block.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
<a name=
|
||||
"expect_non_null-spec">template <class T> T* expect_non_null(T* x);</a>
|
||||
</pre>
|
||||
|
||||
<dl class="expect_non_null-semantics">
|
||||
<dt><b>Returns:</b> <code>x</code></dt>
|
||||
|
||||
<dt><b>Throws:</b> <code><a href=
|
||||
"#error_already_set-spec">error_already_set</a>()</code> iff <code>x ==
|
||||
0</code>.</dt>
|
||||
|
||||
<dt><b>Rationale:</b> Simplifies error-handling when calling functions
|
||||
in the <a href="http://www.python.org/doc/2.2/api/api.html">Python/C
|
||||
API</a> which return 0 on error.</dt>
|
||||
</dl>
|
||||
<pre>
|
||||
<a name="throw_error_already_set-spec">void throw_error_already_set();</a>
|
||||
</pre>
|
||||
|
||||
<dl class="throw_error_already_set-semantics">
|
||||
<dt><b>Effects:</b> <code>throw <a href=
|
||||
"#error_already_set-spec">error_already_set</a>();</code></dt>
|
||||
</dl>
|
||||
|
||||
<dl>
|
||||
<dt><b>Rationale:</b> Many platforms and compilers are not able to
|
||||
consistently catch exceptions thrown across shared library boundaries.
|
||||
Using this function from the Boost.Python library ensures that the
|
||||
appropriate <code>catch</code> block in <code><a href=
|
||||
"#handle_exception-spec">handle_exception</a>()</code> can catch the
|
||||
exception.</dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Examples</h2>
|
||||
<pre>
|
||||
#include <string>
|
||||
#include <boost/python/errors.hpp>
|
||||
#include <boost/python/object.hpp>
|
||||
#include <boost/python/handle.hpp>
|
||||
|
||||
// Returns a std::string which has the same value as obj's "__name__"
|
||||
// attribute.
|
||||
std::string get_name(boost::python::object obj)
|
||||
{
|
||||
// throws if there's no __name__ attribute
|
||||
PyObject* p = boost::python::expect_non_null(
|
||||
PyObject_GetAttrString(obj.ptr(), "__name__"));
|
||||
|
||||
char const* s = PyString_AsString(p);
|
||||
if (s != 0)
|
||||
Py_DECREF(p);
|
||||
|
||||
// throws if it's not a Python string
|
||||
std::string result(
|
||||
boost::python::expect_non_null(
|
||||
PyString_AsString(p)));
|
||||
|
||||
Py_DECREF(p); // Done with p
|
||||
|
||||
return result;
|
||||
}
|
||||
|
||||
//
|
||||
// Demonstrate form 1 of handle_exception
|
||||
//
|
||||
|
||||
// Place into result a Python Int object whose value is 1 if a and b have
|
||||
// identical "__name__" attributes, 0 otherwise.
|
||||
void same_name_impl(PyObject*& result, boost::python::object a, boost::python::object b)
|
||||
{
|
||||
result = PyInt_FromLong(
|
||||
get_name(a) == get_name(a2));
|
||||
}
|
||||
|
||||
object borrowed_object(PyObject* p)
|
||||
{
|
||||
return boost::python::object(
|
||||
boost::python::handle<>(
|
||||
boost::python::borrowed(a1)));
|
||||
}
|
||||
|
||||
// This is an example Python 'C' API interface function
|
||||
extern "C" PyObject*
|
||||
same_name(PyObject* args, PyObject* keywords)
|
||||
{
|
||||
PyObject* a1;
|
||||
PyObject* a2;
|
||||
PyObject* result = 0;
|
||||
|
||||
if (!PyArg_ParseTuple(args, const_cast<char*>("OO"), &a1, &a2))
|
||||
return 0;
|
||||
|
||||
// Use boost::bind to make an object compatible with
|
||||
// boost::Function0<void>
|
||||
if (boost::python::handle_exception(
|
||||
boost::bind<void>(same_name_impl, boost::ref(result), borrowed_object(a1), borrowed_object(a2))))
|
||||
{
|
||||
// an exception was thrown; the Python error was set by
|
||||
// handle_exception()
|
||||
return 0;
|
||||
}
|
||||
|
||||
return result;
|
||||
}
|
||||
|
||||
//
|
||||
// Demonstrate form 2 of handle_exception. Not well-supported by all
|
||||
// compilers.
|
||||
//
|
||||
extern "C" PyObject*
|
||||
same_name2(PyObject* args, PyObject* keywords)
|
||||
{
|
||||
PyObject* a1;
|
||||
PyObject* a2;
|
||||
PyObject* result = 0;
|
||||
|
||||
if (!PyArg_ParseTuple(args, const_cast<char*>("OO"), &a1, &a2))
|
||||
return 0;
|
||||
|
||||
try {
|
||||
return PyInt_FromLong(
|
||||
get_name(borrowed_object(a1)) == get_name(borrowed_object(a2)));
|
||||
}
|
||||
catch(...)
|
||||
{
|
||||
// If an exception was thrown, translate it to Python
|
||||
boost::python::handle_exception();
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
</pre>
|
||||
|
||||
<p>Revised
|
||||
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
||||
13 November, 2002
|
||||
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
||||
</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,148 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python -
|
||||
<boost/python/exception_translator.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header
|
||||
<boost/python/exception_translator.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#functions">Functions</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href=
|
||||
"#register_exception_translator-spec">register_exception_translator</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
<dt><a href="#examples">Example(s)</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>As described <a href="errors.html#handle_exception-spec">here</a>, it
|
||||
is important to make sure that exceptions thrown by C++ code do not pass
|
||||
into the Python interpreter core. By default, Boost.Python translates all
|
||||
C++ exceptions thrown by wrapped functions and module init functions into
|
||||
Python, but the default translators are extremely limited: most C++
|
||||
exceptions will appear in Python as a <a href=
|
||||
"http://www.python.org/doc/current/lib/module-exceptions.html">RuntimeError</a>
|
||||
exception whose representation is
|
||||
<code>'Unidentifiable C++ Exception'</code>. To produce better
|
||||
error messages, users can register additional exception translators as
|
||||
described below.</p>
|
||||
|
||||
<h2><a name="functions"></a>Functions</h2>
|
||||
|
||||
<h3><code><a name="register_exception_translator-spec">register_exception_translator</a></code></h3>
|
||||
|
||||
<pre>
|
||||
<a name="register_exception_translator-spec">template<class ExceptionType, class Translate></a>
|
||||
void register_exception_translator(Translate const& translate);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b></dt>
|
||||
|
||||
<dd>
|
||||
<code>Translate</code> is <a href=
|
||||
"../../../utility/CopyConstructible.html">Copyconstructible</a>, and
|
||||
the following code must be well-formed:
|
||||
<pre>
|
||||
void f(ExceptionType x) { translate(x); }
|
||||
</pre>
|
||||
The expression <code>translate(x)</code> must either throw a C++
|
||||
exception, or a subsequent call to <code><a href=
|
||||
"http://www.python.org/doc/current/api/exceptionHandling.html">PyErr_Occurred</a>()</code>
|
||||
must return 1.
|
||||
</dd>
|
||||
|
||||
<p>
|
||||
|
||||
<dt><b>Effects:</b> Adds a copy of <code>translate</code> to the sequence of
|
||||
exception translators tried when Boost.Python catches an exception that
|
||||
is about to pass into Python's core interpreter. The new translator
|
||||
will get "first shot" at translating all exceptions matching the catch
|
||||
clause shown above. Any subsequently-registered translators will be
|
||||
allowed to translate the exception earlier. A translator which cannot
|
||||
translate a given C++ exception can re-throw it, and it will be handled
|
||||
by a translator which was registered earlier (or by the default
|
||||
translator).</dt>
|
||||
</dl>
|
||||
|
||||
<h2><a name="examples"></a>Example</h2>
|
||||
<pre>
|
||||
#include <boost/python/module.hpp>
|
||||
#include <boost/python/def.hpp>
|
||||
#include <boost/python/exception_translator.hpp>
|
||||
#include <exception>
|
||||
|
||||
struct my_exception : std::exception
|
||||
{
|
||||
char const* what() throw() { return "One of my exceptions"; }
|
||||
};
|
||||
|
||||
void translate(my_exception const& e)
|
||||
{
|
||||
// Use the Python 'C' API to set up an exception object
|
||||
PyErr_SetString(PyExc_RuntimeError, e.what());
|
||||
}
|
||||
|
||||
void something_which_throws()
|
||||
{
|
||||
...
|
||||
throw my_exception();
|
||||
...
|
||||
}
|
||||
|
||||
BOOST_PYTHON_MODULE(exception_translator_ext)
|
||||
{
|
||||
using namespace boost::python;
|
||||
register_exception_translator<my_exception>(&translate);
|
||||
|
||||
def("something_which_throws", something_which_throws);
|
||||
}
|
||||
</pre>
|
||||
<br>
|
||||
<br>
|
||||
|
||||
<hr>
|
||||
|
||||
<p>Revised 03 October, 2002</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
@@ -1,230 +0,0 @@
|
||||
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
||||
|
||||
<html>
|
||||
<head>
|
||||
<meta name="generator" content=
|
||||
"HTML Tidy for Windows (vers 1st August 2002), see www.w3.org">
|
||||
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
|
||||
<link rel="stylesheet" type="text/css" href="../boost.css">
|
||||
|
||||
<title>Boost.Python - <boost/python/extract.hpp></title>
|
||||
</head>
|
||||
|
||||
<body>
|
||||
<table border="0" cellpadding="7" cellspacing="0" width="100%" summary=
|
||||
"header">
|
||||
<tr>
|
||||
<td valign="top" width="300">
|
||||
<h3><a href="../../../../index.htm"><img height="86" width="277"
|
||||
alt="C++ Boost" src="../../../../c++boost.gif" border="0"></a></h3>
|
||||
</td>
|
||||
|
||||
<td valign="top">
|
||||
<h1 align="center"><a href="../index.html">Boost.Python</a></h1>
|
||||
|
||||
<h2 align="center">Header <boost/python/extract.hpp></h2>
|
||||
</td>
|
||||
</tr>
|
||||
</table>
|
||||
<hr>
|
||||
|
||||
<h2>Contents</h2>
|
||||
|
||||
<dl class="page-index">
|
||||
<dt><a href="#introduction">Introduction</a></dt>
|
||||
|
||||
<dt><a href="#classes">Classes</a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#extract-spec">Class <code>extract</code></a></dt>
|
||||
|
||||
<dd>
|
||||
<dl class="page-index">
|
||||
<dt><a href="#extract-spec-synopsis">Class <code>extract</code>
|
||||
synopsis</a></dt>
|
||||
|
||||
<dt><a href="#extract-spec-ctors">Class <code>extract</code>
|
||||
constructors and destructor</a></dt>
|
||||
|
||||
<dt><a href="#extract-spec-observers">Class
|
||||
<code>extract</code> observer functions</a></dt>
|
||||
</dl>
|
||||
</dd>
|
||||
</dl>
|
||||
</dd>
|
||||
|
||||
|
||||
<dt><a href="#examples">Example</a></dt>
|
||||
</dl>
|
||||
<hr>
|
||||
|
||||
<h2><a name="introduction"></a>Introduction</h2>
|
||||
|
||||
<p>Exposes a mechanism for extracting C++ object values from
|
||||
generalized Python objects. Note that
|
||||
<code>extract<</code>...<code>></code> can also be used to
|
||||
"downcast" an <a
|
||||
href="object.html#object-spec">object</a> to some specific <a
|
||||
href="ObjectWrapper.html#ObjectWrapper-concept">ObjectWrapper</a>. Because
|
||||
invoking a mutable python type with an argument of the same type
|
||||
(e.g. <code>list([1,2])</code> typically makes a <em>copy</em> of
|
||||
the argument object, this may be the only way to access the <a
|
||||
href="ObjectWrapper.html#ObjectWrapper-concept">ObjectWrapper</a>'s
|
||||
interface on the original object.
|
||||
|
||||
<h2><a name="classes"></a>Classes</h2>
|
||||
|
||||
<h3><a name="extract-spec"></a>Class template <code>extract</code></h3>
|
||||
|
||||
<p><code>extract<T></code> can be used to extract a value of
|
||||
an arbitrary C++ type from an instance of <code><a
|
||||
href="object.html#object-spec">object</a></code>. Two usages are supported:
|
||||
<ol>
|
||||
<li><b><code>extract<T>(o)</code></b> is a temporary object
|
||||
which is implicitly convertible to <code>T</code> (explicit conversion
|
||||
is also available through the object's function-call
|
||||
operator). However, if no conversion is available which can convert
|
||||
<code>o</code> to an object of type <code>T</code>, a Python
|
||||
<code>TypeError</code> exception will be <a
|
||||
href="definitions.html#raise">raised</a>.
|
||||
|
||||
<li><b><code>extract<T> x(o);</code></b> constructs an extractor
|
||||
whose <code>check()</code> member function can be used to ask whether
|
||||
a conversion is available without causing an exception to be thrown.
|
||||
</ol>
|
||||
|
||||
<h4><a name="extract-spec-synopsis"></a>Class template <code>extract</code>
|
||||
synopsis</h4>
|
||||
<pre>
|
||||
namespace boost { namespace python
|
||||
{
|
||||
template <class T>
|
||||
struct extract
|
||||
{
|
||||
typedef <i>unspecified</i> result_type;
|
||||
|
||||
extract(PyObject*);
|
||||
extract(object const&);
|
||||
|
||||
result_type operator()() const;
|
||||
operator result_type() const;
|
||||
|
||||
bool check() const;
|
||||
};
|
||||
}}
|
||||
</pre>
|
||||
|
||||
<h4><a name="extract-spec-ctors"></a>Class <code>extract</code>
|
||||
constructors and destructor</h4>
|
||||
<pre>
|
||||
extract(PyObject* p);
|
||||
extract(object const&);
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Requires:</b> The first form requires that <code>p</code> is non-null.</dt>
|
||||
|
||||
<dt><b>Effects:</b>Stores a pointer to the Python object managed
|
||||
by its constructor argument. In particular, the reference
|
||||
count of the object is not incremented. The onus is on the user
|
||||
to be sure it is not destroyed before the extractor's conversion
|
||||
function is called.</dt>
|
||||
</dl>
|
||||
|
||||
<h4><a name="extract-spec-observers"></a>Class <code>extract</code>
|
||||
observer functions</h4>
|
||||
<pre>
|
||||
result_type operator()() const;
|
||||
operator result_type() const;
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
<dt><b>Effects:</b> Converts the stored pointer to
|
||||
<code>result_type</code>, which is either <code>T</code> or
|
||||
<code>T const&</code>.
|
||||
</dt>
|
||||
|
||||
<dt><b>Returns:</b> An object of <code>result_type</code>
|
||||
corresponding to the one referenced by the stored pointer.</dt>
|
||||
|
||||
<dt><b>Throws:</b> <code><a
|
||||
href="errors.html#error_already_set-spec">error_already_set</a></code>
|
||||
and sets a <code>TypeError</code> if no such conversion is
|
||||
available. May also emit other unspecified exceptions thrown by
|
||||
the converter which is actually used.</dt>
|
||||
</dl>
|
||||
|
||||
<pre>
|
||||
bool check() const;
|
||||
</pre>
|
||||
|
||||
<dl class="function-semantics">
|
||||
|
||||
<dt><b>Postconditions:</b> None. In particular, note that a
|
||||
return value of <code>true</code> does not preclude an exception
|
||||
being thrown from <code>operator result_type()</code> or
|
||||
<code>operator()()</code>.</dt>
|
||||
|
||||
<dt><b>Returns:</b> <code>false</code> <i>only</i> if no conversion from the
|
||||
stored pointer to <code>T</code> is available.</dt>
|
||||
|
||||
</dl>
|
||||
|
||||
|
||||
<h2><a name="examples"></a>Examples</h2>
|
||||
|
||||
<pre>
|
||||
#include <cstdio>
|
||||
using namespace boost::python;
|
||||
int Print(str s)
|
||||
{
|
||||
// extract a C string from the Python string object
|
||||
char const* c_str = extract<char const*>(s);
|
||||
|
||||
// Print it using printf
|
||||
std::printf("%s\n", c_str);
|
||||
|
||||
// Get the Python string's length and convert it to an int
|
||||
return extract<int>(s.attr("__len__")())
|
||||
}
|
||||
</pre>
|
||||
|
||||
The following example shows how extract can be used along with
|
||||
<code><a
|
||||
href="class.html#class_-spec">class_</a><</code>...<code>></code>
|
||||
to create and access an instance of a wrapped C++ class.
|
||||
|
||||
<pre>
|
||||
struct X
|
||||
{
|
||||
X(int x) : v(x) {}
|
||||
int value() { return v; }
|
||||
private:
|
||||
int v;
|
||||
};
|
||||
|
||||
BOOST_PYTHON_MODULE(extract_ext)
|
||||
{
|
||||
object x_class(
|
||||
class_<X>("X", init<int>())
|
||||
.def("value", &X::value))
|
||||
;
|
||||
|
||||
// Instantiate an X object through the Python interface.
|
||||
// Its lifetime is now managed by x_obj.
|
||||
object x_obj = x_class(3);
|
||||
|
||||
// Get a reference to the C++ object out of the Python object
|
||||
X& x = extract<X&>(x_obj);
|
||||
assert(x.value() == 3);
|
||||
}
|
||||
</pre>
|
||||
<p>Revised 15 November, 2002</p>
|
||||
|
||||
<p><i>© Copyright <a href=
|
||||
"../../../../people/dave_abrahams.htm">Dave Abrahams</a> 2002. All Rights
|
||||
Reserved.</i></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
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