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<!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"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Common Object Structures — Python 2.7.5 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.5 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="Python 2.7.5 documentation" href="../index.html" /> <link rel="up" title="Object Implementation Support" href="objimpl.html" /> <link rel="next" title="Type Objects" href="typeobj.html" /> <link rel="prev" title="Allocating Objects on the Heap" href="allocation.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head> <body> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="typeobj.html" title="Type Objects" accesskey="N">next</a> |</li> <li class="right" > <a href="allocation.html" title="Allocating Objects on the Heap" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >Python/C API Reference Manual</a> »</li> <li><a href="objimpl.html" accesskey="U">Object Implementation Support</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="common-object-structures"> <span id="common-structs"></span><h1>Common Object Structures<a class="headerlink" href="#common-object-structures" title="Permalink to this headline">¶</a></h1> <p>There are a large number of structures which are used in the definition of object types for Python. This section describes these structures and how they are used.</p> <p>All Python objects ultimately share a small number of fields at the beginning of the object’s representation in memory. These are represented by the <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject</span></tt></a> and <a class="reference internal" href="#PyVarObject" title="PyVarObject"><tt class="xref c c-type docutils literal"><span class="pre">PyVarObject</span></tt></a> types, which are defined, in turn, by the expansions of some macros also used, whether directly or indirectly, in the definition of all other Python objects.</p> <dl class="type"> <dt id="PyObject"> <tt class="descname">PyObject</tt><a class="headerlink" href="#PyObject" title="Permalink to this definition">¶</a></dt> <dd><p>All object types are extensions of this type. This is a type which contains the information Python needs to treat a pointer to an object as an object. In a normal “release” build, it contains only the object’s reference count and a pointer to the corresponding type object. It corresponds to the fields defined by the expansion of the <tt class="docutils literal"><span class="pre">PyObject_HEAD</span></tt> macro.</p> </dd></dl> <dl class="type"> <dt id="PyVarObject"> <tt class="descname">PyVarObject</tt><a class="headerlink" href="#PyVarObject" title="Permalink to this definition">¶</a></dt> <dd><p>This is an extension of <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject</span></tt></a> that adds the <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field. This is only used for objects that have some notion of <em>length</em>. This type does not often appear in the Python/C API. It corresponds to the fields defined by the expansion of the <tt class="docutils literal"><span class="pre">PyObject_VAR_HEAD</span></tt> macro.</p> </dd></dl> <p>These macros are used in the definition of <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject</span></tt></a> and <a class="reference internal" href="#PyVarObject" title="PyVarObject"><tt class="xref c c-type docutils literal"><span class="pre">PyVarObject</span></tt></a>:</p> <dl class="macro"> <dt id="PyObject_HEAD"> <tt class="descname">PyObject_HEAD</tt><a class="headerlink" href="#PyObject_HEAD" title="Permalink to this definition">¶</a></dt> <dd><p>This is a macro which expands to the declarations of the fields of the <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject</span></tt></a> type; it is used when declaring new types which represent objects without a varying length. The specific fields it expands to depend on the definition of <tt class="xref c c-macro docutils literal"><span class="pre">Py_TRACE_REFS</span></tt>. By default, that macro is not defined, and <a class="reference internal" href="#PyObject_HEAD" title="PyObject_HEAD"><tt class="xref c c-macro docutils literal"><span class="pre">PyObject_HEAD</span></tt></a> expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span class="n">Py_ssize_t</span> <span class="n">ob_refcnt</span><span class="p">;</span> <span class="n">PyTypeObject</span> <span class="o">*</span><span class="n">ob_type</span><span class="p">;</span> </pre></div> </div> <p>When <tt class="xref c c-macro docutils literal"><span class="pre">Py_TRACE_REFS</span></tt> is defined, it expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span class="n">PyObject</span> <span class="o">*</span><span class="n">_ob_next</span><span class="p">,</span> <span class="o">*</span><span class="n">_ob_prev</span><span class="p">;</span> <span class="n">Py_ssize_t</span> <span class="n">ob_refcnt</span><span class="p">;</span> <span class="n">PyTypeObject</span> <span class="o">*</span><span class="n">ob_type</span><span class="p">;</span> </pre></div> </div> </dd></dl> <dl class="macro"> <dt id="PyObject_VAR_HEAD"> <tt class="descname">PyObject_VAR_HEAD</tt><a class="headerlink" href="#PyObject_VAR_HEAD" title="Permalink to this definition">¶</a></dt> <dd><p>This is a macro which expands to the declarations of the fields of the <a class="reference internal" href="#PyVarObject" title="PyVarObject"><tt class="xref c c-type docutils literal"><span class="pre">PyVarObject</span></tt></a> type; it is used when declaring new types which represent objects with a length that varies from instance to instance. This macro always expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span class="n">PyObject_HEAD</span> <span class="n">Py_ssize_t</span> <span class="n">ob_size</span><span class="p">;</span> </pre></div> </div> <p>Note that <a class="reference internal" href="#PyObject_HEAD" title="PyObject_HEAD"><tt class="xref c c-macro docutils literal"><span class="pre">PyObject_HEAD</span></tt></a> is part of the expansion, and that its own expansion varies depending on the definition of <tt class="xref c c-macro docutils literal"><span class="pre">Py_TRACE_REFS</span></tt>.</p> </dd></dl> <dl class="macro"> <dt id="PyObject_HEAD_INIT"> <tt class="descname">PyObject_HEAD_INIT</tt><big>(</big>type<big>)</big><a class="headerlink" href="#PyObject_HEAD_INIT" title="Permalink to this definition">¶</a></dt> <dd><p>This is a macro which expands to initialization values for a new <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject</span></tt></a> type. This macro expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span class="n">_PyObject_EXTRA_INIT</span> <span class="mi">1</span><span class="p">,</span> <span class="n">type</span><span class="p">,</span> </pre></div> </div> </dd></dl> <dl class="macro"> <dt id="PyVarObject_HEAD_INIT"> <tt class="descname">PyVarObject_HEAD_INIT</tt><big>(</big>type, size<big>)</big><a class="headerlink" href="#PyVarObject_HEAD_INIT" title="Permalink to this definition">¶</a></dt> <dd><p>This is a macro which expands to initialization values for a new <a class="reference internal" href="#PyVarObject" title="PyVarObject"><tt class="xref c c-type docutils literal"><span class="pre">PyVarObject</span></tt></a> type, including the <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field. This macro expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span class="n">_PyObject_EXTRA_INIT</span> <span class="mi">1</span><span class="p">,</span> <span class="n">type</span><span class="p">,</span> <span class="n">size</span><span class="p">,</span> </pre></div> </div> </dd></dl> <dl class="type"> <dt id="PyCFunction"> <tt class="descname">PyCFunction</tt><a class="headerlink" href="#PyCFunction" title="Permalink to this definition">¶</a></dt> <dd><p>Type of the functions used to implement most Python callables in C. Functions of this type take two <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject*</span></tt></a> parameters and return one such value. If the return value is <em>NULL</em>, an exception shall have been set. If not <em>NULL</em>, the return value is interpreted as the return value of the function as exposed in Python. The function must return a new reference.</p> </dd></dl> <dl class="type"> <dt id="PyMethodDef"> <tt class="descname">PyMethodDef</tt><a class="headerlink" href="#PyMethodDef" title="Permalink to this definition">¶</a></dt> <dd><p>Structure used to describe a method of an extension type. This structure has four fields:</p> <table border="1" class="docutils"> <colgroup> <col width="29%" /> <col width="21%" /> <col width="50%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Field</th> <th class="head">C Type</th> <th class="head">Meaning</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><tt class="xref py py-attr docutils literal"><span class="pre">ml_name</span></tt></td> <td>char *</td> <td>name of the method</td> </tr> <tr class="row-odd"><td><tt class="xref py py-attr docutils literal"><span class="pre">ml_meth</span></tt></td> <td>PyCFunction</td> <td>pointer to the C implementation</td> </tr> <tr class="row-even"><td><tt class="xref py py-attr docutils literal"><span class="pre">ml_flags</span></tt></td> <td>int</td> <td>flag bits indicating how the call should be constructed</td> </tr> <tr class="row-odd"><td><tt class="xref py py-attr docutils literal"><span class="pre">ml_doc</span></tt></td> <td>char *</td> <td>points to the contents of the docstring</td> </tr> </tbody> </table> </dd></dl> <p>The <tt class="xref py py-attr docutils literal"><span class="pre">ml_meth</span></tt> is a C function pointer. The functions may be of different types, but they always return <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject*</span></tt></a>. If the function is not of the <a class="reference internal" href="#PyCFunction" title="PyCFunction"><tt class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></tt></a>, the compiler will require a cast in the method table. Even though <a class="reference internal" href="#PyCFunction" title="PyCFunction"><tt class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></tt></a> defines the first parameter as <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject*</span></tt></a>, it is common that the method implementation uses a the specific C type of the <em>self</em> object.</p> <p>The <tt class="xref py py-attr docutils literal"><span class="pre">ml_flags</span></tt> field is a bitfield which can include the following flags. The individual flags indicate either a calling convention or a binding convention. Of the calling convention flags, only <a class="reference internal" href="#METH_VARARGS" title="METH_VARARGS"><tt class="xref py py-const docutils literal"><span class="pre">METH_VARARGS</span></tt></a> and <a class="reference internal" href="#METH_KEYWORDS" title="METH_KEYWORDS"><tt class="xref py py-const docutils literal"><span class="pre">METH_KEYWORDS</span></tt></a> can be combined (but note that <a class="reference internal" href="#METH_KEYWORDS" title="METH_KEYWORDS"><tt class="xref py py-const docutils literal"><span class="pre">METH_KEYWORDS</span></tt></a> alone is equivalent to <tt class="docutils literal"><span class="pre">METH_VARARGS</span> <span class="pre">|</span> <span class="pre">METH_KEYWORDS</span></tt>). Any of the calling convention flags can be combined with a binding flag.</p> <dl class="data"> <dt id="METH_VARARGS"> <tt class="descname">METH_VARARGS</tt><a class="headerlink" href="#METH_VARARGS" title="Permalink to this definition">¶</a></dt> <dd><p>This is the typical calling convention, where the methods have the type <a class="reference internal" href="#PyCFunction" title="PyCFunction"><tt class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></tt></a>. The function expects two <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject*</span></tt></a> values. The first one is the <em>self</em> object for methods; for module functions, it is the module object. The second parameter (often called <em>args</em>) is a tuple object representing all arguments. This parameter is typically processed using <a class="reference internal" href="arg.html#PyArg_ParseTuple" title="PyArg_ParseTuple"><tt class="xref c c-func docutils literal"><span class="pre">PyArg_ParseTuple()</span></tt></a> or <a class="reference internal" href="arg.html#PyArg_UnpackTuple" title="PyArg_UnpackTuple"><tt class="xref c c-func docutils literal"><span class="pre">PyArg_UnpackTuple()</span></tt></a>.</p> </dd></dl> <dl class="data"> <dt id="METH_KEYWORDS"> <tt class="descname">METH_KEYWORDS</tt><a class="headerlink" href="#METH_KEYWORDS" title="Permalink to this definition">¶</a></dt> <dd><p>Methods with these flags must be of type <tt class="xref c c-type docutils literal"><span class="pre">PyCFunctionWithKeywords</span></tt>. The function expects three parameters: <em>self</em>, <em>args</em>, and a dictionary of all the keyword arguments. The flag is typically combined with <a class="reference internal" href="#METH_VARARGS" title="METH_VARARGS"><tt class="xref py py-const docutils literal"><span class="pre">METH_VARARGS</span></tt></a>, and the parameters are typically processed using <a class="reference internal" href="arg.html#PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><tt class="xref c c-func docutils literal"><span class="pre">PyArg_ParseTupleAndKeywords()</span></tt></a>.</p> </dd></dl> <dl class="data"> <dt id="METH_NOARGS"> <tt class="descname">METH_NOARGS</tt><a class="headerlink" href="#METH_NOARGS" title="Permalink to this definition">¶</a></dt> <dd><p>Methods without parameters don’t need to check whether arguments are given if they are listed with the <a class="reference internal" href="#METH_NOARGS" title="METH_NOARGS"><tt class="xref py py-const docutils literal"><span class="pre">METH_NOARGS</span></tt></a> flag. They need to be of type <a class="reference internal" href="#PyCFunction" title="PyCFunction"><tt class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></tt></a>. The first parameter is typically named <tt class="docutils literal"><span class="pre">self</span></tt> and will hold a reference to the module or object instance. In all cases the second parameter will be <em>NULL</em>.</p> </dd></dl> <dl class="data"> <dt id="METH_O"> <tt class="descname">METH_O</tt><a class="headerlink" href="#METH_O" title="Permalink to this definition">¶</a></dt> <dd><p>Methods with a single object argument can be listed with the <a class="reference internal" href="#METH_O" title="METH_O"><tt class="xref py py-const docutils literal"><span class="pre">METH_O</span></tt></a> flag, instead of invoking <a class="reference internal" href="arg.html#PyArg_ParseTuple" title="PyArg_ParseTuple"><tt class="xref c c-func docutils literal"><span class="pre">PyArg_ParseTuple()</span></tt></a> with a <tt class="docutils literal"><span class="pre">"O"</span></tt> argument. They have the type <a class="reference internal" href="#PyCFunction" title="PyCFunction"><tt class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></tt></a>, with the <em>self</em> parameter, and a <a class="reference internal" href="#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject*</span></tt></a> parameter representing the single argument.</p> </dd></dl> <dl class="data"> <dt id="METH_OLDARGS"> <tt class="descname">METH_OLDARGS</tt><a class="headerlink" href="#METH_OLDARGS" title="Permalink to this definition">¶</a></dt> <dd><p>This calling convention is deprecated. The method must be of type <a class="reference internal" href="#PyCFunction" title="PyCFunction"><tt class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></tt></a>. The second argument is <em>NULL</em> if no arguments are given, a single object if exactly one argument is given, and a tuple of objects if more than one argument is given. There is no way for a function using this convention to distinguish between a call with multiple arguments and a call with a tuple as the only argument.</p> </dd></dl> <p>These two constants are not used to indicate the calling convention but the binding when use with methods of classes. These may not be used for functions defined for modules. At most one of these flags may be set for any given method.</p> <dl class="data"> <dt id="METH_CLASS"> <tt class="descname">METH_CLASS</tt><a class="headerlink" href="#METH_CLASS" title="Permalink to this definition">¶</a></dt> <dd><p id="index-0">The method will be passed the type object as the first parameter rather than an instance of the type. This is used to create <em>class methods</em>, similar to what is created when using the <a class="reference internal" href="../library/functions.html#classmethod" title="classmethod"><tt class="xref py py-func docutils literal"><span class="pre">classmethod()</span></tt></a> built-in function.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.3.</span></p> </dd></dl> <dl class="data"> <dt id="METH_STATIC"> <tt class="descname">METH_STATIC</tt><a class="headerlink" href="#METH_STATIC" title="Permalink to this definition">¶</a></dt> <dd><p id="index-1">The method will be passed <em>NULL</em> as the first parameter rather than an instance of the type. This is used to create <em>static methods</em>, similar to what is created when using the <a class="reference internal" href="../library/functions.html#staticmethod" title="staticmethod"><tt class="xref py py-func docutils literal"><span class="pre">staticmethod()</span></tt></a> built-in function.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.3.</span></p> </dd></dl> <p>One other constant controls whether a method is loaded in place of another definition with the same method name.</p> <dl class="data"> <dt id="METH_COEXIST"> <tt class="descname">METH_COEXIST</tt><a class="headerlink" href="#METH_COEXIST" title="Permalink to this definition">¶</a></dt> <dd><p>The method will be loaded in place of existing definitions. Without <em>METH_COEXIST</em>, the default is to skip repeated definitions. Since slot wrappers are loaded before the method table, the existence of a <em>sq_contains</em> slot, for example, would generate a wrapped method named <a class="reference internal" href="../reference/datamodel.html#object.__contains__" title="object.__contains__"><tt class="xref py py-meth docutils literal"><span class="pre">__contains__()</span></tt></a> and preclude the loading of a corresponding PyCFunction with the same name. With the flag defined, the PyCFunction will be loaded in place of the wrapper object and will co-exist with the slot. This is helpful because calls to PyCFunctions are optimized more than wrapper object calls.</p> <p class="versionadded"> <span class="versionmodified">New in version 2.4.</span></p> </dd></dl> <dl class="type"> <dt id="PyMemberDef"> <tt class="descname">PyMemberDef</tt><a class="headerlink" href="#PyMemberDef" title="Permalink to this definition">¶</a></dt> <dd><p>Structure which describes an attribute of a type which corresponds to a C struct member. Its fields are:</p> <table border="1" class="docutils"> <colgroup> <col width="29%" /> <col width="21%" /> <col width="50%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Field</th> <th class="head">C Type</th> <th class="head">Meaning</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><tt class="xref py py-attr docutils literal"><span class="pre">name</span></tt></td> <td>char *</td> <td>name of the member</td> </tr> <tr class="row-odd"><td><a class="reference internal" href="../library/functions.html#type" title="type"><tt class="xref py py-attr docutils literal"><span class="pre">type</span></tt></a></td> <td>int</td> <td>the type of the member in the C struct</td> </tr> <tr class="row-even"><td><tt class="xref py py-attr docutils literal"><span class="pre">offset</span></tt></td> <td>Py_ssize_t</td> <td>the offset in bytes that the member is located on the type’s object struct</td> </tr> <tr class="row-odd"><td><tt class="xref py py-attr docutils literal"><span class="pre">flags</span></tt></td> <td>int</td> <td>flag bits indicating if the field should be read-only or writable</td> </tr> <tr class="row-even"><td><tt class="xref py py-attr docutils literal"><span class="pre">doc</span></tt></td> <td>char *</td> <td>points to the contents of the docstring</td> </tr> </tbody> </table> <p><a class="reference internal" href="../library/functions.html#type" title="type"><tt class="xref py py-attr docutils literal"><span class="pre">type</span></tt></a> can be one of many <tt class="docutils literal"><span class="pre">T_</span></tt> macros corresponding to various C types. When the member is accessed in Python, it will be converted to the equivalent Python type.</p> <table border="1" class="docutils"> <colgroup> <col width="45%" /> <col width="55%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Macro name</th> <th class="head">C type</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td>T_SHORT</td> <td>short</td> </tr> <tr class="row-odd"><td>T_INT</td> <td>int</td> </tr> <tr class="row-even"><td>T_LONG</td> <td>long</td> </tr> <tr class="row-odd"><td>T_FLOAT</td> <td>float</td> </tr> <tr class="row-even"><td>T_DOUBLE</td> <td>double</td> </tr> <tr class="row-odd"><td>T_STRING</td> <td>char *</td> </tr> <tr class="row-even"><td>T_OBJECT</td> <td>PyObject *</td> </tr> <tr class="row-odd"><td>T_OBJECT_EX</td> <td>PyObject *</td> </tr> <tr class="row-even"><td>T_CHAR</td> <td>char</td> </tr> <tr class="row-odd"><td>T_BYTE</td> <td>char</td> </tr> <tr class="row-even"><td>T_UBYTE</td> <td>unsigned char</td> </tr> <tr class="row-odd"><td>T_UINT</td> <td>unsigned int</td> </tr> <tr class="row-even"><td>T_USHORT</td> <td>unsigned short</td> </tr> <tr class="row-odd"><td>T_ULONG</td> <td>unsigned long</td> </tr> <tr class="row-even"><td>T_BOOL</td> <td>char</td> </tr> <tr class="row-odd"><td>T_LONGLONG</td> <td>long long</td> </tr> <tr class="row-even"><td>T_ULONGLONG</td> <td>unsigned long long</td> </tr> <tr class="row-odd"><td>T_PYSSIZET</td> <td>Py_ssize_t</td> </tr> </tbody> </table> <p><tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></tt> and <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></tt> differ in that <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></tt> returns <tt class="docutils literal"><span class="pre">None</span></tt> if the member is <em>NULL</em> and <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></tt> raises an <a class="reference internal" href="../library/exceptions.html#exceptions.AttributeError" title="exceptions.AttributeError"><tt class="xref py py-exc docutils literal"><span class="pre">AttributeError</span></tt></a>. Try to use <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></tt> over <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></tt> because <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></tt> handles use of the <a class="reference internal" href="../reference/simple_stmts.html#del"><tt class="xref std std-keyword docutils literal"><span class="pre">del</span></tt></a> statement on that attribute more correctly than <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></tt>.</p> <p><tt class="xref py py-attr docutils literal"><span class="pre">flags</span></tt> can be 0 for write and read access or <tt class="xref c c-macro docutils literal"><span class="pre">READONLY</span></tt> for read-only access. Using <tt class="xref c c-macro docutils literal"><span class="pre">T_STRING</span></tt> for <a class="reference internal" href="../library/functions.html#type" title="type"><tt class="xref py py-attr docutils literal"><span class="pre">type</span></tt></a> implies <tt class="xref c c-macro docutils literal"><span class="pre">READONLY</span></tt>. Only <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></tt> and <tt class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></tt> members can be deleted. (They are set to <em>NULL</em>).</p> </dd></dl> <dl class="function"> <dt id="Py_FindMethod"> <a class="reference internal" href="#PyObject" title="PyObject">PyObject</a>* <tt class="descname">Py_FindMethod</tt><big>(</big><a class="reference internal" href="#PyMethodDef" title="PyMethodDef">PyMethodDef</a><em> table[]</em>, <a class="reference internal" href="#PyObject" title="PyObject">PyObject</a><em> *ob</em>, char<em> *name</em><big>)</big><a class="headerlink" href="#Py_FindMethod" title="Permalink to this definition">¶</a></dt> <dd><em class="refcount">Return value: New reference.</em><p>Return a bound method object for an extension type implemented in C. This can be useful in the implementation of a <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt> or <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattr</span></tt> handler that does not use the <a class="reference internal" href="object.html#PyObject_GenericGetAttr" title="PyObject_GenericGetAttr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GenericGetAttr()</span></tt></a> function.</p> </dd></dl> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="allocation.html" title="previous chapter">Allocating Objects on the Heap</a></p> <h4>Next topic</h4> <p class="topless"><a href="typeobj.html" title="next chapter">Type Objects</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/c-api/structures.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="typeobj.html" title="Type Objects" >next</a> |</li> <li class="right" > <a href="allocation.html" title="Allocating Objects on the Heap" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >Python/C API Reference Manual</a> »</li> <li><a href="objimpl.html" >Object Implementation Support</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2020, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="http://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Oct 13, 2020. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>