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<div class="section" id="common-object-structures">
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<span id="common-structs"></span><h1>Common Object Structures<a class="headerlink" href="#common-object-structures" title="Permalink to this headline">¶</a></h1>
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<p>There are a large number of structures which are used in the definition of
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object types for Python. This section describes these structures and how they
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are used.</p>
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<p>All Python objects ultimately share a small number of fields at the beginning
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of the object’s representation in memory. These are represented by the
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<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,
|
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by the expansions of some macros also used, whether directly or indirectly, in
|
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the definition of all other Python objects.</p>
|
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<dl class="type">
|
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<dt id="c.PyObject">
|
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<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 notranslate"><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 notranslate"><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 notranslate"><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 notranslate"><span class="pre">Py_TYPE</span></code></a>.</p>
|
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</dd></dl>
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<dl class="type">
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<dt id="c.PyVarObject">
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<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>
|
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field. This is only used for objects that have some notion of <em>length</em>.
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||
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 notranslate"><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 notranslate"><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 notranslate"><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 notranslate"><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 notranslate"><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 notranslate"><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 notranslate"><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 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>
|
||
</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>
|
||
</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>
|
||
</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.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
|
||
with signature <code class="xref py py-const docutils literal notranslate"><span class="pre">METH_VARARGS</span> <span class="pre">|</span> <span class="pre">METH_KEYWORDS</span></code>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="type">
|
||
<dt id="c._PyCFunctionFast">
|
||
<code class="descname">_PyCFunctionFast</code><a class="headerlink" href="#c._PyCFunctionFast" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Type of the functions used to implement Python callables in C
|
||
with signature <a class="reference internal" href="#METH_FASTCALL" title="METH_FASTCALL"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_FASTCALL</span></code></a>.</p>
|
||
</dd></dl>
|
||
|
||
<dl class="type">
|
||
<dt id="c._PyCFunctionFastWithKeywords">
|
||
<code class="descname">_PyCFunctionFastWithKeywords</code><a class="headerlink" href="#c._PyCFunctionFastWithKeywords" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Type of the functions used to implement Python callables in C
|
||
with signature <code class="xref py py-const docutils literal notranslate"><span class="pre">METH_FASTCALL</span> <span class="pre">|</span> <span class="pre">METH_KEYWORDS</span></code>.</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 class="docutils align-center">
|
||
<colgroup>
|
||
<col style="width: 28%" />
|
||
<col style="width: 23%" />
|
||
<col style="width: 48%" />
|
||
</colgroup>
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Field</p></th>
|
||
<th class="head"><p>C Type</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_name</span></code></p></td>
|
||
<td><p>const char *</p></td>
|
||
<td><p>name of the method</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_meth</span></code></p></td>
|
||
<td><p>PyCFunction</p></td>
|
||
<td><p>pointer to the C
|
||
implementation</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_flags</span></code></p></td>
|
||
<td><p>int</p></td>
|
||
<td><p>flag bits indicating how the
|
||
call should be constructed</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">ml_doc</span></code></p></td>
|
||
<td><p>const char *</p></td>
|
||
<td><p>points to the contents of the
|
||
docstring</p></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.</p>
|
||
<p>There are four basic calling conventions for positional arguments
|
||
and two of them can be combined with <code class="xref py py-const docutils literal notranslate"><span class="pre">METH_KEYWORDS</span></code> to support
|
||
also keyword arguments. So there are a total of 6 calling conventions:</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>
|
||
<code class="descname">METH_VARARGS | METH_KEYWORDS</code></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 notranslate"><span class="pre">PyCFunctionWithKeywords</span></code></a>.
|
||
The function expects three parameters: <em>self</em>, <em>args</em>, <em>kwargs</em> where
|
||
<em>kwargs</em> is a dictionary of all the keyword arguments or possibly <em>NULL</em>
|
||
if there are no keyword arguments. 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_FASTCALL">
|
||
<code class="descname">METH_FASTCALL</code><a class="headerlink" href="#METH_FASTCALL" title="Permalink to this definition">¶</a></dt>
|
||
<dd><p>Fast calling convention supporting only positional arguments.
|
||
The methods have the type <a class="reference internal" href="#c._PyCFunctionFast" title="_PyCFunctionFast"><code class="xref c c-type docutils literal notranslate"><span class="pre">_PyCFunctionFast</span></code></a>.
|
||
The first parameter is <em>self</em>, the second parameter is a C array
|
||
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> values indicating the arguments and the third
|
||
parameter is the number of arguments (the length of the array).</p>
|
||
<p>This is not part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">limited API</span></a>.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7.</span></p>
|
||
</div>
|
||
</dd></dl>
|
||
|
||
<dl class="data">
|
||
<dt>
|
||
<code class="descname">METH_FASTCALL | METH_KEYWORDS</code></dt>
|
||
<dd><p>Extension of <a class="reference internal" href="#METH_FASTCALL" title="METH_FASTCALL"><code class="xref py py-const docutils literal notranslate"><span class="pre">METH_FASTCALL</span></code></a> supporting also keyword arguments,
|
||
with methods of type <a class="reference internal" href="#c._PyCFunctionFastWithKeywords" title="_PyCFunctionFastWithKeywords"><code class="xref c c-type docutils literal notranslate"><span class="pre">_PyCFunctionFastWithKeywords</span></code></a>.
|
||
Keyword arguments are passed the same way as in the vectorcall protocol:
|
||
there is an additional fourth <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
|
||
which is a tuple representing the names of the keyword arguments
|
||
or possibly <em>NULL</em> if there are no keywords. The values of the keyword
|
||
arguments are stored in the <em>args</em> array, after the positional arguments.</p>
|
||
<p>This is not part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">limited API</span></a>.</p>
|
||
<div class="versionadded">
|
||
<p><span class="versionmodified added">New in version 3.7.</span></p>
|
||
</div>
|
||
</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 <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 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>
|
||
|
||
<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>
|
||
</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>
|
||
</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>
|
||
</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 class="docutils align-center">
|
||
<colgroup>
|
||
<col style="width: 28%" />
|
||
<col style="width: 23%" />
|
||
<col style="width: 48%" />
|
||
</colgroup>
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Field</p></th>
|
||
<th class="head"><p>C Type</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">name</span></code></p></td>
|
||
<td><p>const char *</p></td>
|
||
<td><p>name of the member</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></p></td>
|
||
<td><p>int</p></td>
|
||
<td><p>the type of the member in the
|
||
C struct</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">offset</span></code></p></td>
|
||
<td><p>Py_ssize_t</p></td>
|
||
<td><p>the offset in bytes that the
|
||
member is located on the
|
||
type’s object struct</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">flags</span></code></p></td>
|
||
<td><p>int</p></td>
|
||
<td><p>flag bits indicating if the
|
||
field should be read-only or
|
||
writable</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p><code class="xref py py-attr docutils literal notranslate"><span class="pre">doc</span></code></p></td>
|
||
<td><p>const char *</p></td>
|
||
<td><p>points to the contents of the
|
||
docstring</p></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 class="docutils align-center">
|
||
<colgroup>
|
||
<col style="width: 45%" />
|
||
<col style="width: 55%" />
|
||
</colgroup>
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Macro name</p></th>
|
||
<th class="head"><p>C type</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p>T_SHORT</p></td>
|
||
<td><p>short</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_INT</p></td>
|
||
<td><p>int</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_LONG</p></td>
|
||
<td><p>long</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_FLOAT</p></td>
|
||
<td><p>float</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_DOUBLE</p></td>
|
||
<td><p>double</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_STRING</p></td>
|
||
<td><p>const char *</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_OBJECT</p></td>
|
||
<td><p>PyObject *</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_OBJECT_EX</p></td>
|
||
<td><p>PyObject *</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_CHAR</p></td>
|
||
<td><p>char</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_BYTE</p></td>
|
||
<td><p>char</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_UBYTE</p></td>
|
||
<td><p>unsigned char</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_UINT</p></td>
|
||
<td><p>unsigned int</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_USHORT</p></td>
|
||
<td><p>unsigned short</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_ULONG</p></td>
|
||
<td><p>unsigned long</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_BOOL</p></td>
|
||
<td><p>char</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_LONGLONG</p></td>
|
||
<td><p>long long</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>T_ULONGLONG</p></td>
|
||
<td><p>unsigned long long</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>T_PYSSIZET</p></td>
|
||
<td><p>Py_ssize_t</p></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#AttributeError" title="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>. <code class="xref c c-macro docutils literal notranslate"><span class="pre">T_STRING</span></code> data is interpreted as UTF-8.
|
||
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 class="docutils align-center">
|
||
<colgroup>
|
||
<col style="width: 20%" />
|
||
<col style="width: 27%" />
|
||
<col style="width: 53%" />
|
||
</colgroup>
|
||
<thead>
|
||
<tr class="row-odd"><th class="head"><p>Field</p></th>
|
||
<th class="head"><p>C Type</p></th>
|
||
<th class="head"><p>Meaning</p></th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr class="row-even"><td><p>name</p></td>
|
||
<td><p>const char *</p></td>
|
||
<td><p>attribute name</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>get</p></td>
|
||
<td><p>getter</p></td>
|
||
<td><p>C Function to get the attribute</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>set</p></td>
|
||
<td><p>setter</p></td>
|
||
<td><p>optional C function to set or
|
||
delete the attribute, if omitted
|
||
the attribute is readonly</p></td>
|
||
</tr>
|
||
<tr class="row-odd"><td><p>doc</p></td>
|
||
<td><p>const char *</p></td>
|
||
<td><p>optional docstring</p></td>
|
||
</tr>
|
||
<tr class="row-even"><td><p>closure</p></td>
|
||
<td><p>void *</p></td>
|
||
<td><p>optional function pointer,
|
||
providing additional data for
|
||
getter and setter</p></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>
|
||
|
||
</div>
|
||
|
||
|
||
</div>
|
||
</div>
|
||
</div>
|
||
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|
||
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|
||
<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>
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||
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||
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||
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||
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