OwlCyberSecurity - MANAGER
Edit File: structures.html
<!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="X-UA-Compatible" content="IE=Edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Common Object Structures — Python 2.7.18 documentation</title> <link rel="stylesheet" href="../_static/classic.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></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/language_data.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 2.7.18 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.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" /> <link rel="canonical" href="file:///usr/share/doc/python2.7/html/c-api/structures.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <div id="outdated-warning" style="padding: .5em; text-align: center; background-color: #FFBABA; color: #6A0E0E;"> This document is for an old version of Python that is <a href="https://devguide.python.org/devcycle/#end-of-life-branches">no longer supported</a>. You should install the python3 and python3-doc packages and read the <a href="file:///usr/share/doc/python3-doc/html/c-api/structures.html"> Python documentation for the Python3 version packaged in this release</a>. </div> <div class="related" role="navigation" aria-label="related navigation"> <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="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >Python/C API Reference Manual</a> »</li> <li class="nav-item nav-item-2"><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" role="main"> <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="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> and <a class="reference internal" href="#c.PyVarObject" title="PyVarObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyVarObject</span></code></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="c.PyObject"> <code class="descname">PyObject</code><a class="headerlink" href="#c.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 <code class="docutils literal notranslate"><span class="pre">PyObject_HEAD</span></code> macro.</p> </dd></dl> <dl class="type"> <dt id="c.PyVarObject"> <code class="descname">PyVarObject</code><a class="headerlink" href="#c.PyVarObject" title="Permalink to this definition">¶</a></dt> <dd><p>This is an extension of <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> that adds the <code class="xref py py-attr docutils literal notranslate"><span class="pre">ob_size</span></code> 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 <code class="docutils literal notranslate"><span class="pre">PyObject_VAR_HEAD</span></code> macro.</p> </dd></dl> <p>These macros are used in the definition of <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> and <a class="reference internal" href="#c.PyVarObject" title="PyVarObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyVarObject</span></code></a>:</p> <dl class="macro"> <dt id="c.PyObject_HEAD"> <code class="descname">PyObject_HEAD</code><a class="headerlink" href="#c.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="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></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 <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_TRACE_REFS</span></code>. By default, that macro is not defined, and <a class="reference internal" href="#c.PyObject_HEAD" title="PyObject_HEAD"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyObject_HEAD</span></code></a> expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></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> <p>When <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_TRACE_REFS</span></code> is defined, it expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><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="c.PyObject_VAR_HEAD"> <code class="descname">PyObject_VAR_HEAD</code><a class="headerlink" href="#c.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="#c.PyVarObject" title="PyVarObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyVarObject</span></code></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 notranslate"><div class="highlight"><pre><span></span><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="#c.PyObject_HEAD" title="PyObject_HEAD"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyObject_HEAD</span></code></a> is part of the expansion, and that its own expansion varies depending on the definition of <code class="xref c c-macro docutils literal notranslate"><span class="pre">Py_TRACE_REFS</span></code>.</p> </dd></dl> <dl class="macro"> <dt id="c.Py_TYPE"> <code class="descname">Py_TYPE</code><span class="sig-paren">(</span>o<span class="sig-paren">)</span><a class="headerlink" href="#c.Py_TYPE" title="Permalink to this definition">¶</a></dt> <dd><p>This macro is used to access the <code class="xref py py-attr docutils literal notranslate"><span class="pre">ob_type</span></code> member of a Python object. It expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">(((</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)(</span><span class="n">o</span><span class="p">))</span><span class="o">-></span><span class="n">ob_type</span><span class="p">)</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 2.6.</span></p> </div> </dd></dl> <dl class="macro"> <dt id="c.Py_REFCNT"> <code class="descname">Py_REFCNT</code><span class="sig-paren">(</span>o<span class="sig-paren">)</span><a class="headerlink" href="#c.Py_REFCNT" title="Permalink to this definition">¶</a></dt> <dd><p>This macro is used to access the <code class="xref py py-attr docutils literal notranslate"><span class="pre">ob_refcnt</span></code> member of a Python object. It expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">(((</span><span class="n">PyObject</span><span class="o">*</span><span class="p">)(</span><span class="n">o</span><span class="p">))</span><span class="o">-></span><span class="n">ob_refcnt</span><span class="p">)</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 2.6.</span></p> </div> </dd></dl> <dl class="macro"> <dt id="c.Py_SIZE"> <code class="descname">Py_SIZE</code><span class="sig-paren">(</span>o<span class="sig-paren">)</span><a class="headerlink" href="#c.Py_SIZE" title="Permalink to this definition">¶</a></dt> <dd><p>This macro is used to access the <code class="xref py py-attr docutils literal notranslate"><span class="pre">ob_size</span></code> member of a Python object. It expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="p">(((</span><span class="n">PyVarObject</span><span class="o">*</span><span class="p">)(</span><span class="n">o</span><span class="p">))</span><span class="o">-></span><span class="n">ob_size</span><span class="p">)</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 2.6.</span></p> </div> </dd></dl> <dl class="macro"> <dt id="c.PyObject_HEAD_INIT"> <code class="descname">PyObject_HEAD_INIT</code><span class="sig-paren">(</span>type<span class="sig-paren">)</span><a class="headerlink" href="#c.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="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> type. This macro expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><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="c.PyVarObject_HEAD_INIT"> <code class="descname">PyVarObject_HEAD_INIT</code><span class="sig-paren">(</span>type, size<span class="sig-paren">)</span><a class="headerlink" href="#c.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="#c.PyVarObject" title="PyVarObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyVarObject</span></code></a> type, including the <code class="xref py py-attr docutils literal notranslate"><span class="pre">ob_size</span></code> field. This macro expands to:</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><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="c.PyCFunction"> <code class="descname">PyCFunction</code><a class="headerlink" href="#c.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="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></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="c.PyMethodDef"> <code class="descname">PyMethodDef</code><a class="headerlink" href="#c.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><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_name</span></code></td> <td>char *</td> <td>name of the method</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_meth</span></code></td> <td>PyCFunction</td> <td>pointer to the C implementation</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_flags</span></code></td> <td>int</td> <td>flag bits indicating how the call should be constructed</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_doc</span></code></td> <td>char *</td> <td>points to the contents of the docstring</td> </tr> </tbody> </table> </dd></dl> <p>The <code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_meth</span></code> is a C function pointer. The functions may be of different types, but they always return <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></a>. If the function is not of the <a class="reference internal" href="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunction</span></code></a>, the compiler will require a cast in the method table. Even though <a class="reference internal" href="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunction</span></code></a> defines the first parameter as <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></a>, it is common that the method implementation uses the specific C type of the <em>self</em> object.</p> <p>The <code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_flags</span></code> 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"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_VARARGS</span></code></a> and <a class="reference internal" href="#METH_KEYWORDS" title="METH_KEYWORDS"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_KEYWORDS</span></code></a> can be combined. Any of the calling convention flags can be combined with a binding flag.</p> <dl class="data"> <dt id="METH_VARARGS"> <code class="descname">METH_VARARGS</code><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="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunction</span></code></a>. The function expects two <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></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#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyArg_ParseTuple()</span></code></a> or <a class="reference internal" href="arg.html#c.PyArg_UnpackTuple" title="PyArg_UnpackTuple"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyArg_UnpackTuple()</span></code></a>.</p> </dd></dl> <dl class="data"> <dt id="METH_KEYWORDS"> <code class="descname">METH_KEYWORDS</code><a class="headerlink" href="#METH_KEYWORDS" title="Permalink to this definition">¶</a></dt> <dd><p>Methods with these flags must be of type <code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunctionWithKeywords</span></code>. 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"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_VARARGS</span></code></a>, and the parameters are typically processed using <a class="reference internal" href="arg.html#c.PyArg_ParseTupleAndKeywords" title="PyArg_ParseTupleAndKeywords"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyArg_ParseTupleAndKeywords()</span></code></a>.</p> </dd></dl> <dl class="data"> <dt id="METH_NOARGS"> <code class="descname">METH_NOARGS</code><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"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_NOARGS</span></code></a> flag. They need to be of type <a class="reference internal" href="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunction</span></code></a>. The first parameter is typically named <code class="docutils literal notranslate"><span class="pre">self</span></code> 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"> <code class="descname">METH_O</code><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"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_O</span></code></a> flag, instead of invoking <a class="reference internal" href="arg.html#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyArg_ParseTuple()</span></code></a> with a <code class="docutils literal notranslate"><span class="pre">"O"</span></code> argument. They have the type <a class="reference internal" href="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunction</span></code></a>, with the <em>self</em> parameter, and a <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></a> parameter representing the single argument.</p> </dd></dl> <dl class="data"> <dt id="METH_OLDARGS"> <code class="descname">METH_OLDARGS</code><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="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyCFunction</span></code></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"> <code class="descname">METH_CLASS</code><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"><code class="xref py py-func docutils literal notranslate"><span class="pre">classmethod()</span></code></a> built-in function.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 2.3.</span></p> </div> </dd></dl> <dl class="data"> <dt id="METH_STATIC"> <code class="descname">METH_STATIC</code><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"><code class="xref py py-func docutils literal notranslate"><span class="pre">staticmethod()</span></code></a> built-in function.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 2.3.</span></p> </div> </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"> <code class="descname">METH_COEXIST</code><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__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__contains__()</span></code></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> <div class="versionadded"> <p><span class="versionmodified">New in version 2.4.</span></p> </div> </dd></dl> <dl class="type"> <dt id="c.PyMemberDef"> <code class="descname">PyMemberDef</code><a class="headerlink" href="#c.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><code class="xref py py-attr docutils literal notranslate"><span class="pre">name</span></code></td> <td>char *</td> <td>name of the member</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></td> <td>int</td> <td>the type of the member in the C struct</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">offset</span></code></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><code class="xref py py-attr docutils literal notranslate"><span class="pre">flags</span></code></td> <td>int</td> <td>flag bits indicating if the field should be read-only or writable</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">doc</span></code></td> <td>char *</td> <td>points to the contents of the docstring</td> </tr> </tbody> </table> <p><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code> can be one of many <code class="docutils literal notranslate"><span class="pre">T_</span></code> 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><code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT</span></code> and <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT_EX</span></code> differ in that <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT</span></code> returns <code class="docutils literal notranslate"><span class="pre">None</span></code> if the member is <em>NULL</em> and <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT_EX</span></code> raises an <a class="reference internal" href="../library/exceptions.html#exceptions.AttributeError" title="exceptions.AttributeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">AttributeError</span></code></a>. Try to use <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT_EX</span></code> over <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT</span></code> because <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT_EX</span></code> handles use of the <a class="reference internal" href="../reference/simple_stmts.html#del"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">del</span></code></a> statement on that attribute more correctly than <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT</span></code>.</p> <p><code class="xref py py-attr docutils literal notranslate"><span class="pre">flags</span></code> can be <code class="docutils literal notranslate"><span class="pre">0</span></code> for write and read access or <code class="xref c c-macro docutils literal notranslate"><span class="pre">READONLY</span></code> for read-only access. Using <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_STRING</span></code> for <a class="reference internal" href="../library/functions.html#type" title="type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> implies <code class="xref c c-macro docutils literal notranslate"><span class="pre">READONLY</span></code>. Only <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT</span></code> and <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_OBJECT_EX</span></code> members can be deleted. (They are set to <em>NULL</em>).</p> </dd></dl> <dl class="type"> <dt id="c.PyGetSetDef"> <code class="descname">PyGetSetDef</code><a class="headerlink" href="#c.PyGetSetDef" title="Permalink to this definition">¶</a></dt> <dd><p>Structure to define property-like access for a type. See also description of the <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_getset" title="PyTypeObject.tp_getset"><code class="xref c c-member docutils literal notranslate"><span class="pre">PyTypeObject.tp_getset</span></code></a> slot.</p> <table border="1" class="docutils"> <colgroup> <col width="20%" /> <col width="27%" /> <col width="53%" /> </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>name</td> <td>char *</td> <td>attribute name</td> </tr> <tr class="row-odd"><td>get</td> <td>getter</td> <td>C Function to get the attribute</td> </tr> <tr class="row-even"><td>set</td> <td>setter</td> <td>optional C function to set or delete the attribute, if omitted the attribute is readonly</td> </tr> <tr class="row-odd"><td>doc</td> <td>char *</td> <td>optional docstring</td> </tr> <tr class="row-even"><td>closure</td> <td>void *</td> <td>optional function pointer, providing additional data for getter and setter</td> </tr> </tbody> </table> <p>The <code class="docutils literal notranslate"><span class="pre">get</span></code> function takes one <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></a> parameter (the instance) and a function pointer (the associated <code class="docutils literal notranslate"><span class="pre">closure</span></code>):</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="k">typedef</span> <span class="n">PyObject</span> <span class="o">*</span><span class="p">(</span><span class="o">*</span><span class="n">getter</span><span class="p">)(</span><span class="n">PyObject</span> <span class="o">*</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="p">);</span> </pre></div> </div> <p>It should return a new reference on success or <em>NULL</em> with a set exception on failure.</p> <p><code class="docutils literal notranslate"><span class="pre">set</span></code> functions take two <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject*</span></code></a> parameters (the instance and the value to be set) and a function pointer (the associated <code class="docutils literal notranslate"><span class="pre">closure</span></code>):</p> <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="k">typedef</span> <span class="nf">int</span> <span class="p">(</span><span class="o">*</span><span class="n">setter</span><span class="p">)(</span><span class="n">PyObject</span> <span class="o">*</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="p">);</span> </pre></div> </div> <p>In case the attribute should be deleted the second parameter is <em>NULL</em>. Should return <code class="docutils literal notranslate"><span class="pre">0</span></code> on success or <code class="docutils literal notranslate"><span class="pre">-1</span></code> with a set exception on failure.</p> </dd></dl> <dl class="function"> <dt id="c.Py_FindMethod"> <a class="reference internal" href="#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">Py_FindMethod</code><span class="sig-paren">(</span><a class="reference internal" href="#c.PyMethodDef" title="PyMethodDef">PyMethodDef</a><em> table[]</em>, <a class="reference internal" href="#c.PyObject" title="PyObject">PyObject</a><em> *ob</em>, char<em> *name</em><span class="sig-paren">)</span><a class="headerlink" href="#c.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 <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_getattro" title="PyTypeObject.tp_getattro"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_getattro</span></code></a> or <a class="reference internal" href="typeobj.html#c.PyTypeObject.tp_getattr" title="PyTypeObject.tp_getattr"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_getattr</span></code></a> handler that does not use the <a class="reference internal" href="object.html#c.PyObject_GenericGetAttr" title="PyObject_GenericGetAttr"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyObject_GenericGetAttr()</span></code></a> function.</p> </dd></dl> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <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> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../_sources/c-api/structures.rst.txt" rel="nofollow">Show Source</a></li> </ul> </div> <div id="searchbox" style="display: none" role="search"> <h3>Quick search</h3> <div class="searchformwrapper"> <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> </div> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related" role="navigation" aria-label="related navigation"> <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="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.18 documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" >Python/C API Reference Manual</a> »</li> <li class="nav-item nav-item-2"><a href="objimpl.html" >Object Implementation Support</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2024, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="https://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on December 09, 2024. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.8.5. </div> </body> </html>