File: //usr/share/doc/python-docs-2.4.3/html/ext/node33.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="ext.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="ext.html" title='Extending and Embedding the Python Interpreter' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="prev" href="node32.html" />
<link rel="parent" href="dnt-type-methods.html" />
<link rel="next" href="building.html" />
<meta name='aesop' content='information' />
<title>2.2.6 More Suggestions</title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="2.2.5 Abstract Protocol Support"
href="node32.html"><img src='../icons/previous.png'
border='0' height='32' alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="2.2 Type Methods"
href="dnt-type-methods.html"><img src='../icons/up.png'
border='0' height='32' alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="3. Building C and"
href="building.html"><img src='../icons/next.png'
border='0' height='32' alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Extending and Embedding the Python Interpreter</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
href="contents.html"><img src='../icons/contents.png'
border='0' height='32' alt='Contents' width='32' /></A></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="node32.html">2.2.5 Abstract Protocol Support</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="dnt-type-methods.html">2.2 Type Methods</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="building.html">3. Building C and</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->
<H2><A NAME="SECTION004260000000000000000">
2.2.6 More Suggestions</A>
</H2>
<P>
Remember that you can omit most of these functions, in which case you
provide <code>0</code> as a value. There are type definitions for each of
the functions you must provide. They are in <span class="file">object.h</span> in the
Python include directory that comes with the source distribution of
Python.
<P>
In order to learn how to implement any specific method for your new
data type, do the following: Download and unpack the Python source
distribution. Go the <span class="file">Objects</span> directory, then search the
C source files for <code>tp_</code> plus the function you want (for
example, <code>tp_print</code> or <code>tp_compare</code>). You will find
examples of the function you want to implement.
<P>
When you need to verify that an object is an instance of the type
you are implementing, use the <tt class="cfunction">PyObject_TypeCheck</tt> function.
A sample of its use might be something like the following:
<P>
<div class="verbatim"><pre>
if (! PyObject_TypeCheck(some_object, &MyType)) {
PyErr_SetString(PyExc_TypeError, "arg #1 not a mything");
return NULL;
}
</pre></div>
<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="2.2.5 Abstract Protocol Support"
href="node32.html"><img src='../icons/previous.png'
border='0' height='32' alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="2.2 Type Methods"
href="dnt-type-methods.html"><img src='../icons/up.png'
border='0' height='32' alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="3. Building C and"
href="building.html"><img src='../icons/next.png'
border='0' height='32' alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Extending and Embedding the Python Interpreter</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
href="contents.html"><img src='../icons/contents.png'
border='0' height='32' alt='Contents' width='32' /></A></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
<td class='online-navigation'><img src='../icons/blank.png'
border='0' height='32' alt='' width='32' /></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="node32.html">2.2.5 Abstract Protocol Support</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="dnt-type-methods.html">2.2 Type Methods</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="building.html">3. Building C and</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.3, documentation updated on 29 March 2006.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>