<!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 3.5.3 documentation</title> <link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '3.5.3', 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 3.5.3 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 3.5.3 documentation" href="../contents.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> <script type="text/javascript" src="../_static/version_switch.js"></script> </head> <body role="document"> <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> <span class="version_switcher_placeholder">3.5.3</span> <a href="../index.html">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> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" 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> <script type="text/javascript">$('.inline-search').show(0);</script> | </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"><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"><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. Nothing is actually declared to be a <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal"><span class="pre">PyObject</span></code></a>, but every pointer to a Python object can be cast to a <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal"><span class="pre">PyObject*</span></code></a>. Access to the members must be done by using the macros <a class="reference internal" href="#c.Py_REFCNT" title="Py_REFCNT"><code class="xref c c-macro docutils literal"><span class="pre">Py_REFCNT</span></code></a> and <a class="reference internal" href="#c.Py_TYPE" title="Py_TYPE"><code class="xref c c-macro docutils literal"><span class="pre">Py_TYPE</span></code></a>.</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"><span class="pre">PyObject</span></code></a> that adds the <code class="xref py py-attr docutils literal"><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. Access to the members must be done by using the macros <a class="reference internal" href="#c.Py_REFCNT" title="Py_REFCNT"><code class="xref c c-macro docutils literal"><span class="pre">Py_REFCNT</span></code></a>, <a class="reference internal" href="#c.Py_TYPE" title="Py_TYPE"><code class="xref c c-macro docutils literal"><span class="pre">Py_TYPE</span></code></a>, and <a class="reference internal" href="#c.Py_SIZE" title="Py_SIZE"><code class="xref c c-macro docutils literal"><span class="pre">Py_SIZE</span></code></a>.</p> </dd></dl> <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 used when declaring new types which represent objects without a varying length. The PyObject_HEAD macro expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span></span><span class="n">PyObject</span> <span class="n">ob_base</span><span class="p">;</span> </pre></div> </div> <p>See documentation of <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal"><span class="pre">PyObject</span></code></a> above.</p> </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 used when declaring new types which represent objects with a length that varies from instance to instance. The PyObject_VAR_HEAD macro expands to:</p> <div class="highlight-c"><div class="highlight"><pre><span></span><span class="n">PyVarObject</span> <span class="n">ob_base</span><span class="p">;</span> </pre></div> </div> <p>See documentation of <a class="reference internal" href="#c.PyVarObject" title="PyVarObject"><code class="xref c c-type docutils literal"><span class="pre">PyVarObject</span></code></a> above.</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"><span class="pre">ob_type</span></code> member of a Python object. It expands to:</p> <div class="highlight-c"><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> </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"><span class="pre">ob_refcnt</span></code> member of a Python object. It expands to:</p> <div class="highlight-c"><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> </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"><span class="pre">ob_size</span></code> member of a Python object. It expands to:</p> <div class="highlight-c"><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> </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"><span class="pre">PyObject</span></code></a> type. This macro expands to:</p> <div class="highlight-c"><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"><span class="pre">PyVarObject</span></code></a> type, including the <code class="xref py py-attr docutils literal"><span class="pre">ob_size</span></code> field. This macro expands to:</p> <div class="highlight-c"><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"><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.PyCFunctionWithKeywords"> <code class="descname">PyCFunctionWithKeywords</code><a class="headerlink" href="#c.PyCFunctionWithKeywords" title="Permalink to this definition">¶</a></dt> <dd><p>Type of the functions used to implement Python callables in C that take keyword arguments: they take three <a class="reference internal" href="#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal"><span class="pre">PyObject*</span></code></a> parameters and return one such value. See <a class="reference internal" href="#c.PyCFunction" title="PyCFunction"><code class="xref c c-type docutils literal"><span class="pre">PyCFunction</span></code></a> above for the meaning of the return value.</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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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"><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 <a class="reference internal" href="#c.PyCFunctionWithKeywords" title="PyCFunctionWithKeywords"><code class="xref c c-type docutils literal"><span class="pre">PyCFunctionWithKeywords</span></code></a>. The function expects three parameters: <em>self</em>, <em>args</em>, and a dictionary of all the keyword arguments. The flag must be combined with <a class="reference internal" href="#METH_VARARGS" title="METH_VARARGS"><code class="xref py py-const docutils literal"><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"><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"><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"><span class="pre">PyCFunction</span></code></a>. The first parameter is typically named <em>self</em> 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"><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"><span class="pre">PyArg_ParseTuple()</span></code></a> with a <code class="docutils literal"><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"><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"><span class="pre">PyObject*</span></code></a> parameter representing the single 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"><span class="pre">classmethod()</span></code></a> built-in function.</p> </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"><span class="pre">staticmethod()</span></code></a> built-in function.</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"> <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"><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> </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"><span class="pre">name</span></code></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"><code class="xref py py-attr docutils literal"><span class="pre">type</span></code></a></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"><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"><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"><span class="pre">doc</span></code></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"><code class="xref py py-attr docutils literal"><span class="pre">type</span></code></a> can be one of many <code class="docutils literal"><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"><span class="pre">T_OBJECT</span></code> and <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></code> differ in that <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></code> returns <code class="docutils literal"><span class="pre">None</span></code> if the member is <em>NULL</em> and <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></code> raises an <a class="reference internal" href="../library/exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal"><span class="pre">AttributeError</span></code></a>. Try to use <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></code> over <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></code> because <code class="xref c c-macro docutils literal"><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"><span class="pre">del</span></code></a> statement on that attribute more correctly than <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></code>.</p> <p><code class="xref py py-attr docutils literal"><span class="pre">flags</span></code> can be <code class="docutils literal"><span class="pre">0</span></code> for write and read access or <code class="xref c c-macro docutils literal"><span class="pre">READONLY</span></code> for read-only access. Using <code class="xref c c-macro docutils literal"><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"><span class="pre">type</span></code></a> implies <code class="xref c c-macro docutils literal"><span class="pre">READONLY</span></code>. Only <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT</span></code> and <code class="xref c c-macro docutils literal"><span class="pre">T_OBJECT_EX</span></code> members can be deleted. (They are set to <em>NULL</em>).</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="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/c-api/structures.txt" rel="nofollow">Show Source</a></li> </ul> </div> </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> <span class="version_switcher_placeholder">3.5.3</span> <a href="../index.html">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> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" 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> <script type="text/javascript">$('.inline-search').show(0);</script> | </li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 2001-2017, 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 Jan 20, 2017. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.3.3. </div> </body> </html>