mirror of
https://github.com/boostorg/python.git
synced 2026-01-21 17:12:22 +00:00
190 lines
5.5 KiB
HTML
190 lines
5.5 KiB
HTML
<!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/to_python_converter.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">Boost.Python</h1>
|
|
|
|
<h2 align="center">Header <boost/python/to_python_converter.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="#to_python_converter-spec">Class Template <code>to_python_converter</code></a>
|
|
|
|
<dd>
|
|
<dl class="page-index">
|
|
|
|
<dt><a href="#to_python_converter-spec-synopsis">Class Template
|
|
<code>to_python_converter</code> synopsis</a>
|
|
|
|
<dt><a href="#to_python_converter-spec-ctors">Class Template
|
|
<code>to_python_converter</code> constructor</a>
|
|
</dl>
|
|
</dl>
|
|
|
|
<dt><a href="#examples">Example</a>
|
|
</dl>
|
|
<hr>
|
|
|
|
<h2><a name="introduction"></a>Introduction</h2>
|
|
|
|
<code>to_python_converter</code> registers a conversion from
|
|
objects of a given C++ type into a Python object.
|
|
|
|
<h2><a name="classes"></a>Classes</h2>
|
|
|
|
<h3><a name="to_python_converter-spec"></a>Class template <code>to_python_converter</code></h3>
|
|
|
|
<code>to_python_converter</code> adds a wrapper around a static
|
|
member function of its second template parameter, handling
|
|
low-level details such as insertion into the converter registry.
|
|
|
|
<table border="1" summary="to_python_converter template parameters">
|
|
<caption>
|
|
<b><code>to_python_converter</code> template parameters</b><br>
|
|
In the table below, <b><code>x</code></b> denotes an object of type <code>T</code>
|
|
</caption>
|
|
<tr>
|
|
<th>Parameter
|
|
|
|
<th>Requirements
|
|
|
|
<th>Description
|
|
|
|
<tr>
|
|
<td><code>T</code>
|
|
|
|
<td>
|
|
|
|
<td>The C++ type of the source object in the conversion
|
|
|
|
<tr>
|
|
<td><code>Conversion</code>
|
|
|
|
<td><code>PyObject* p = Conversion::convert(x)</code>,<br>
|
|
if <code>p == 0</code>, <code><a href="http://www.python.org/doc/2.2/api/exceptionHandling.html#l2h-71">PyErr_Occurred</a>() != 0</code>.
|
|
|
|
<td>A class type whose static member function
|
|
<code>convert</code> does the real work of the conversion.
|
|
|
|
<tr>
|
|
</table>
|
|
|
|
<h4><a name="to_python_converter-spec-synopsis"></a>Class template <code>to_python_converter</code> synopsis</h4>
|
|
<pre>
|
|
namespace boost { namespace python
|
|
{
|
|
template <class T, class Conversion>
|
|
struct to_python_converter
|
|
{
|
|
to_python_converter();
|
|
};
|
|
}}
|
|
</pre>
|
|
|
|
<h4><a name="to_python_converter-spec-ctors"></a>Class template <code>to_python_converter</code> constructor</h4>
|
|
<pre>
|
|
to_python_converter();
|
|
</pre>
|
|
|
|
<dl class="function-semantics">
|
|
|
|
<dt><b>Effects:</b> Registers a to_python converter which uses
|
|
<code>Conversion::convert()</code> to do its work.
|
|
|
|
</dl>
|
|
|
|
<h2><a name="examples"></a>Example</h2>
|
|
|
|
This example presumes that someone has implemented the standard <a
|
|
href="http://www.python.org/doc/2.2/ext/dnt-basics.html">noddy example
|
|
module</a> from the Python documentation, and placed the corresponding
|
|
declarations in <code>"noddy.h"</code>. Because
|
|
<code>noddy_NoddyObject</code> is the ultimate trivial extension type,
|
|
the example is a bit contrived: it wraps a function for which all
|
|
information is contained in the <i>type</i> of its return value.
|
|
|
|
<h3>C++ module definition</h3>
|
|
|
|
<pre>
|
|
#include <boost/python/reference.hpp>
|
|
#include <boost/python/module.hpp>
|
|
#include "noddy.h"
|
|
|
|
struct tag {};
|
|
tag make_tag() { return tag(); }
|
|
|
|
using namespace boost::python;
|
|
|
|
struct tag_to_noddy
|
|
{
|
|
static PyObject* convert(tag const& x)
|
|
{
|
|
return PyObject_New(noddy_NoddyObject, &noddy_NoddyType);
|
|
}
|
|
};
|
|
|
|
BOOST_PYTHON_MODULE_INIT(to_python_converter)
|
|
{
|
|
module to_python("to_python_converter")
|
|
.def("make_tag", make_tag)
|
|
;
|
|
to_python_converter<tag, tag_to_noddy>();
|
|
}
|
|
</pre>
|
|
|
|
<h3>Python code</h3>
|
|
|
|
<pre>
|
|
>>> import to_python_converter
|
|
>>> def always_none():
|
|
... return None
|
|
...
|
|
>>> def choose_function(x):
|
|
... if (x % 2 != 0):
|
|
... return to_python_converter.make_tag
|
|
... else:
|
|
... return always_none
|
|
...
|
|
>>> a = [ choose_function(x) for x in range(5) ]
|
|
>>> b = [ f() for f in a ]
|
|
>>> type(b[0])
|
|
<type 'NoneType'>
|
|
>>> type(b[1])
|
|
<type 'Noddy'>
|
|
>>> type(b[2])
|
|
<type 'NoneType'>
|
|
>>> type(b[3])
|
|
<type 'Noddy'>
|
|
</pre>
|
|
|
|
<p>Revised
|
|
<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
|
|
05 November, 2001
|
|
<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
|
|
|
|
|
|
<p><i>© Copyright <a href="../../../../people/dave_abrahams.htm">Dave
|
|
Abrahams</a> 2002. All Rights Reserved.</i>
|
|
|