boost/python
2
0
Fork 0
mirror of https://github.com/boostorg/python.git synced 2026-02-02 09:02:15 +00:00
Code Issues Projects Releases Wiki Activity

clean up v1 flotsam

Browse Source 
[SVN r15856]
This commit is contained in:
Dave Abrahams
2002-10-10 13:05:52 +00:00
parent a8d37ebc4a
commit 64035277dc
15 changed files with 0 additions and 3259 deletions
Download Patch File Download Diff File Expand all files Collapse all files

73
doc/extending.html
View File

@@ -1,73 +0,0 @@
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>
A Brief Introduction to writing Python extension modules
</title>
<h1>
<img src="../../../c++boost.gif" alt="c++boost.gif (8819 bytes)" align="center"
width="277" height="86">
</h1>
<h1>
A Brief Introduction to writing Python extension modules
</h1>
<p>
Interfacing any language to Python involves building a module which can
be loaded by the Python interpreter, but which isn't written in Python.
This is known as an <em>extension module</em>. Many of the <a href=
"http://www.python.org/doc/current/lib/lib.html">built-in Python
libraries</a> are constructed in 'C' this way; Python even supplies its
<a href="http://www.python.org/doc/current/lib/types.html">fundamental
types</a> using the same mechanism. An extension module can be statically
linked with the Python interpreter, but it more commonly resides in a
shared library or DLL.
<p>
As you can see from <a href=
"http://www.python.org/doc/current/ext/ext.html"> The Python Extending
and Embedding Tutorial</a>, writing an extension module normally means
worrying about
<ul>
<li>
<a href="http://www.python.org/doc/current/ext/refcounts.html">
maintaining reference counts</a>
<li>
<a href="http://www.python.org/doc/current/ext/callingPython.html"> how
to call back into Python</a>
<li>
<a href="http://www.python.org/doc/current/ext/parseTuple.html">
function argument parsing and typechecking</a>
</ul>
This last item typically occupies a great deal of code in an extension
module. Remember that Python is a completely dynamic language. A callable
object receives its arguments in a tuple; it is up to that object to extract
those arguments from the tuple, check their types, and raise appropriate
exceptions. There are numerous other tedious details that need to be
managed; too many to mention here. The Boost Python Library is designed to
lift most of that burden.<br>
<br>
<p>
Another obstacle that most people run into eventually when extending
Python is that there's no way to make a true Python class in an extension
module. The typical solution is to create a new Python type in the
extension module, and then write an additional module in 100% Python. The
Python module defines a Python class which dispatches to an instance of
the extension type, which it contains. This allows users to write
subclasses of the class in the Python module, almost as though they were
sublcassing the extension type. Aside from being tedious, it's not really
the same as having a true class, because there's no way for the user to
override a method of the extension type which is called from the
extension module. Boost.Python solves this problem by taking advantage of <a
href="http://www.python.org/doc/essays/metaclasses/">Python's metaclass
feature</a> to provide objects which look, walk, and hiss almost exactly
like regular Python classes. Boost.Python classes are actually cleaner than
Python classes in some subtle ways; a more detailed discussion will
follow (someday).</p>
<p>Next: <a href="comparisons.html">Comparisons with Other Systems</a> Up: <a
href="index.html">Top</a> </p>
<p>
&copy; Copyright David Abrahams 2000. 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>