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<div class="section" id="type-objects">
<span id="type-structs"></span><h1>Type Objects<a class="headerlink" href="#type-objects" title="Permalink to this headline">¶</a></h1>
<p>Perhaps one of the most important structures of the Python object system is the
structure that defines a new type: the <a class="reference internal" href="type.html#PyTypeObject" title="PyTypeObject"><tt class="xref c c-type docutils literal"><span class="pre">PyTypeObject</span></tt></a> structure. Type
objects can be handled using any of the <tt class="xref c c-func docutils literal"><span class="pre">PyObject_*()</span></tt> or
<tt class="xref c c-func docutils literal"><span class="pre">PyType_*()</span></tt> functions, but do not offer much that’s interesting to most
Python applications. These objects are fundamental to how objects behave, so
they are very important to the interpreter itself and to any extension module
that implements new types.</p>
<p>Type objects are fairly large compared to most of the standard types. The reason
for the size is that each type object stores a large number of values, mostly C
function pointers, each of which implements a small part of the type’s
functionality. The fields of the type object are examined in detail in this
section. The fields will be described in the order in which they occur in the
structure.</p>
<p>Typedefs: unaryfunc, binaryfunc, ternaryfunc, inquiry, intargfunc,
intintargfunc, intobjargproc, intintobjargproc, objobjargproc, destructor,
freefunc, printfunc, getattrfunc, getattrofunc, setattrfunc, setattrofunc,
reprfunc, hashfunc</p>
<p>The structure definition for <a class="reference internal" href="type.html#PyTypeObject" title="PyTypeObject"><tt class="xref c c-type docutils literal"><span class="pre">PyTypeObject</span></tt></a> can be found in
<tt class="file docutils literal"><span class="pre">Include/object.h</span></tt>. For convenience of reference, this repeats the
definition found there:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="k">typedef</span> <span class="k">struct</span> <span class="n">_typeobject</span> <span class="p">{</span>
<span class="n">PyObject_VAR_HEAD</span>
<span class="kt">char</span> <span class="o">*</span><span class="n">tp_name</span><span class="p">;</span> <span class="cm">/* For printing, in format "<module>.<name>" */</span>
<span class="kt">int</span> <span class="n">tp_basicsize</span><span class="p">,</span> <span class="n">tp_itemsize</span><span class="p">;</span> <span class="cm">/* For allocation */</span>
<span class="cm">/* Methods to implement standard operations */</span>
<span class="n">destructor</span> <span class="n">tp_dealloc</span><span class="p">;</span>
<span class="n">printfunc</span> <span class="n">tp_print</span><span class="p">;</span>
<span class="n">getattrfunc</span> <span class="n">tp_getattr</span><span class="p">;</span>
<span class="n">setattrfunc</span> <span class="n">tp_setattr</span><span class="p">;</span>
<span class="kt">void</span> <span class="o">*</span><span class="n">tp_reserved</span><span class="p">;</span>
<span class="n">reprfunc</span> <span class="n">tp_repr</span><span class="p">;</span>
<span class="cm">/* Method suites for standard classes */</span>
<span class="n">PyNumberMethods</span> <span class="o">*</span><span class="n">tp_as_number</span><span class="p">;</span>
<span class="n">PySequenceMethods</span> <span class="o">*</span><span class="n">tp_as_sequence</span><span class="p">;</span>
<span class="n">PyMappingMethods</span> <span class="o">*</span><span class="n">tp_as_mapping</span><span class="p">;</span>
<span class="cm">/* More standard operations (here for binary compatibility) */</span>
<span class="n">hashfunc</span> <span class="n">tp_hash</span><span class="p">;</span>
<span class="n">ternaryfunc</span> <span class="n">tp_call</span><span class="p">;</span>
<span class="n">reprfunc</span> <span class="n">tp_str</span><span class="p">;</span>
<span class="n">getattrofunc</span> <span class="n">tp_getattro</span><span class="p">;</span>
<span class="n">setattrofunc</span> <span class="n">tp_setattro</span><span class="p">;</span>
<span class="cm">/* Functions to access object as input/output buffer */</span>
<span class="n">PyBufferProcs</span> <span class="o">*</span><span class="n">tp_as_buffer</span><span class="p">;</span>
<span class="cm">/* Flags to define presence of optional/expanded features */</span>
<span class="kt">long</span> <span class="n">tp_flags</span><span class="p">;</span>
<span class="kt">char</span> <span class="o">*</span><span class="n">tp_doc</span><span class="p">;</span> <span class="cm">/* Documentation string */</span>
<span class="cm">/* call function for all accessible objects */</span>
<span class="n">traverseproc</span> <span class="n">tp_traverse</span><span class="p">;</span>
<span class="cm">/* delete references to contained objects */</span>
<span class="n">inquiry</span> <span class="n">tp_clear</span><span class="p">;</span>
<span class="cm">/* rich comparisons */</span>
<span class="n">richcmpfunc</span> <span class="n">tp_richcompare</span><span class="p">;</span>
<span class="cm">/* weak reference enabler */</span>
<span class="kt">long</span> <span class="n">tp_weaklistoffset</span><span class="p">;</span>
<span class="cm">/* Iterators */</span>
<span class="n">getiterfunc</span> <span class="n">tp_iter</span><span class="p">;</span>
<span class="n">iternextfunc</span> <span class="n">tp_iternext</span><span class="p">;</span>
<span class="cm">/* Attribute descriptor and subclassing stuff */</span>
<span class="k">struct</span> <span class="n">PyMethodDef</span> <span class="o">*</span><span class="n">tp_methods</span><span class="p">;</span>
<span class="k">struct</span> <span class="n">PyMemberDef</span> <span class="o">*</span><span class="n">tp_members</span><span class="p">;</span>
<span class="k">struct</span> <span class="n">PyGetSetDef</span> <span class="o">*</span><span class="n">tp_getset</span><span class="p">;</span>
<span class="k">struct</span> <span class="n">_typeobject</span> <span class="o">*</span><span class="n">tp_base</span><span class="p">;</span>
<span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_dict</span><span class="p">;</span>
<span class="n">descrgetfunc</span> <span class="n">tp_descr_get</span><span class="p">;</span>
<span class="n">descrsetfunc</span> <span class="n">tp_descr_set</span><span class="p">;</span>
<span class="kt">long</span> <span class="n">tp_dictoffset</span><span class="p">;</span>
<span class="n">initproc</span> <span class="n">tp_init</span><span class="p">;</span>
<span class="n">allocfunc</span> <span class="n">tp_alloc</span><span class="p">;</span>
<span class="n">newfunc</span> <span class="n">tp_new</span><span class="p">;</span>
<span class="n">freefunc</span> <span class="n">tp_free</span><span class="p">;</span> <span class="cm">/* Low-level free-memory routine */</span>
<span class="n">inquiry</span> <span class="n">tp_is_gc</span><span class="p">;</span> <span class="cm">/* For PyObject_IS_GC */</span>
<span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_bases</span><span class="p">;</span>
<span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_mro</span><span class="p">;</span> <span class="cm">/* method resolution order */</span>
<span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_cache</span><span class="p">;</span>
<span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_subclasses</span><span class="p">;</span>
<span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_weaklist</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyTypeObject</span><span class="p">;</span>
</pre></div>
</div>
<p>The type object structure extends the <a class="reference internal" href="structures.html#PyVarObject" title="PyVarObject"><tt class="xref c c-type docutils literal"><span class="pre">PyVarObject</span></tt></a> structure. The
<tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field is used for dynamic types (created by <tt class="xref py py-func docutils literal"><span class="pre">type_new()</span></tt>,
usually called from a class statement). Note that <a class="reference internal" href="type.html#PyType_Type" title="PyType_Type"><tt class="xref c c-data docutils literal"><span class="pre">PyType_Type</span></tt></a> (the
metatype) initializes <tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt>, which means that its instances (i.e.
type objects) <em>must</em> have the <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field.</p>
<dl class="member">
<dt id="PyObject._ob_next">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyObject._ob_next</tt><a class="headerlink" href="#PyObject._ob_next" title="Permalink to this definition">¶</a></dt>
<dt id="PyObject._ob_prev">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyObject._ob_prev</tt><a class="headerlink" href="#PyObject._ob_prev" title="Permalink to this definition">¶</a></dt>
<dd><p>These fields are only present when the macro <tt class="docutils literal"><span class="pre">Py_TRACE_REFS</span></tt> is defined.
Their initialization to <em>NULL</em> is taken care of by the <tt class="docutils literal"><span class="pre">PyObject_HEAD_INIT</span></tt>
macro. For statically allocated objects, these fields always remain <em>NULL</em>.
For dynamically allocated objects, these two fields are used to link the object
into a doubly-linked list of <em>all</em> live objects on the heap. This could be used
for various debugging purposes; currently the only use is to print the objects
that are still alive at the end of a run when the environment variable
<span class="target" id="index-0"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONDUMPREFS"><tt class="xref std std-envvar docutils literal"><span class="pre">PYTHONDUMPREFS</span></tt></a> is set.</p>
<p>These fields are not inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyObject.ob_refcnt">
Py_ssize_t <tt class="descname">PyObject.ob_refcnt</tt><a class="headerlink" href="#PyObject.ob_refcnt" title="Permalink to this definition">¶</a></dt>
<dd><p>This is the type object’s reference count, initialized to <tt class="docutils literal"><span class="pre">1</span></tt> by the
<tt class="docutils literal"><span class="pre">PyObject_HEAD_INIT</span></tt> macro. Note that for statically allocated type objects,
the type’s instances (objects whose <tt class="xref py py-attr docutils literal"><span class="pre">ob_type</span></tt> points back to the type) do
<em>not</em> count as references. But for dynamically allocated type objects, the
instances <em>do</em> count as references.</p>
<p>This field is not inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyObject.ob_type">
<a class="reference internal" href="type.html#PyTypeObject" title="PyTypeObject">PyTypeObject</a>* <tt class="descname">PyObject.ob_type</tt><a class="headerlink" href="#PyObject.ob_type" title="Permalink to this definition">¶</a></dt>
<dd><p>This is the type’s type, in other words its metatype. It is initialized by the
argument to the <tt class="docutils literal"><span class="pre">PyObject_HEAD_INIT</span></tt> macro, and its value should normally be
<tt class="docutils literal"><span class="pre">&PyType_Type</span></tt>. However, for dynamically loadable extension modules that must
be usable on Windows (at least), the compiler complains that this is not a valid
initializer. Therefore, the convention is to pass <em>NULL</em> to the
<tt class="docutils literal"><span class="pre">PyObject_HEAD_INIT</span></tt> macro and to initialize this field explicitly at the
start of the module’s initialization function, before doing anything else. This
is typically done like this:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">Foo_Type</span><span class="p">.</span><span class="n">ob_type</span> <span class="o">=</span> <span class="o">&</span><span class="n">PyType_Type</span><span class="p">;</span>
</pre></div>
</div>
<p>This should be done before any instances of the type are created.
<a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a> checks if <tt class="xref py py-attr docutils literal"><span class="pre">ob_type</span></tt> is <em>NULL</em>, and if so,
initializes it to the <tt class="xref py py-attr docutils literal"><span class="pre">ob_type</span></tt> field of the base class.
<a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a> will not change this field if it is non-zero.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyVarObject.ob_size">
Py_ssize_t <tt class="descname">PyVarObject.ob_size</tt><a class="headerlink" href="#PyVarObject.ob_size" title="Permalink to this definition">¶</a></dt>
<dd><p>For statically allocated type objects, this should be initialized to zero. For
dynamically allocated type objects, this field has a special internal meaning.</p>
<p>This field is not inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_name">
char* <tt class="descname">PyTypeObject.tp_name</tt><a class="headerlink" href="#PyTypeObject.tp_name" title="Permalink to this definition">¶</a></dt>
<dd><p>Pointer to a NUL-terminated string containing the name of the type. For types
that are accessible as module globals, the string should be the full module
name, followed by a dot, followed by the type name; for built-in types, it
should be just the type name. If the module is a submodule of a package, the
full package name is part of the full module name. For example, a type named
<tt class="xref py py-class docutils literal"><span class="pre">T</span></tt> defined in module <tt class="xref py py-mod docutils literal"><span class="pre">M</span></tt> in subpackage <tt class="xref py py-mod docutils literal"><span class="pre">Q</span></tt> in package <tt class="xref py py-mod docutils literal"><span class="pre">P</span></tt>
should have the <tt class="xref py py-attr docutils literal"><span class="pre">tp_name</span></tt> initializer <tt class="docutils literal"><span class="pre">"P.Q.M.T"</span></tt>.</p>
<p>For dynamically allocated type objects, this should just be the type name, and
the module name explicitly stored in the type dict as the value for key
<tt class="docutils literal"><span class="pre">'__module__'</span></tt>.</p>
<p>For statically allocated type objects, the tp_name field should contain a dot.
Everything before the last dot is made accessible as the <tt class="xref py py-attr docutils literal"><span class="pre">__module__</span></tt>
attribute, and everything after the last dot is made accessible as the
<tt class="xref py py-attr docutils literal"><span class="pre">__name__</span></tt> attribute.</p>
<p>If no dot is present, the entire <tt class="xref py py-attr docutils literal"><span class="pre">tp_name</span></tt> field is made accessible as the
<tt class="xref py py-attr docutils literal"><span class="pre">__name__</span></tt> attribute, and the <tt class="xref py py-attr docutils literal"><span class="pre">__module__</span></tt> attribute is undefined
(unless explicitly set in the dictionary, as explained above). This means your
type will be impossible to pickle.</p>
<p>This field is not inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_basicsize">
Py_ssize_t <tt class="descname">PyTypeObject.tp_basicsize</tt><a class="headerlink" href="#PyTypeObject.tp_basicsize" title="Permalink to this definition">¶</a></dt>
<dt id="PyTypeObject.tp_itemsize">
Py_ssize_t <tt class="descname">PyTypeObject.tp_itemsize</tt><a class="headerlink" href="#PyTypeObject.tp_itemsize" title="Permalink to this definition">¶</a></dt>
<dd><p>These fields allow calculating the size in bytes of instances of the type.</p>
<p>There are two kinds of types: types with fixed-length instances have a zero
<tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt> field, types with variable-length instances have a non-zero
<tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt> field. For a type with fixed-length instances, all
instances have the same size, given in <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt>.</p>
<p>For a type with variable-length instances, the instances must have an
<tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field, and the instance size is <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt> plus N
times <tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt>, where N is the “length” of the object. The value of
N is typically stored in the instance’s <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field. There are
exceptions: for example, ints use a negative <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> to indicate a
negative number, and N is <tt class="docutils literal"><span class="pre">abs(ob_size)</span></tt> there. Also, the presence of an
<tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field in the instance layout doesn’t mean that the instance
structure is variable-length (for example, the structure for the list type has
fixed-length instances, yet those instances have a meaningful <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt>
field).</p>
<p>The basic size includes the fields in the instance declared by the macro
<a class="reference internal" href="structures.html#PyObject_HEAD" title="PyObject_HEAD"><tt class="xref c c-macro docutils literal"><span class="pre">PyObject_HEAD</span></tt></a> or <a class="reference internal" href="structures.html#PyObject_VAR_HEAD" title="PyObject_VAR_HEAD"><tt class="xref c c-macro docutils literal"><span class="pre">PyObject_VAR_HEAD</span></tt></a> (whichever is used to
declare the instance struct) and this in turn includes the <tt class="xref py py-attr docutils literal"><span class="pre">_ob_prev</span></tt> and
<tt class="xref py py-attr docutils literal"><span class="pre">_ob_next</span></tt> fields if they are present. This means that the only correct
way to get an initializer for the <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt> is to use the
<tt class="docutils literal"><span class="pre">sizeof</span></tt> operator on the struct used to declare the instance layout.
The basic size does not include the GC header size.</p>
<p>These fields are inherited separately by subtypes. If the base type has a
non-zero <tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt>, it is generally not safe to set
<tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt> to a different non-zero value in a subtype (though this
depends on the implementation of the base type).</p>
<p>A note about alignment: if the variable items require a particular alignment,
this should be taken care of by the value of <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt>. Example:
suppose a type implements an array of <tt class="docutils literal"><span class="pre">double</span></tt>. <tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt> is
<tt class="docutils literal"><span class="pre">sizeof(double)</span></tt>. It is the programmer’s responsibility that
<tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt> is a multiple of <tt class="docutils literal"><span class="pre">sizeof(double)</span></tt> (assuming this is the
alignment requirement for <tt class="docutils literal"><span class="pre">double</span></tt>).</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_dealloc">
destructor <tt class="descname">PyTypeObject.tp_dealloc</tt><a class="headerlink" href="#PyTypeObject.tp_dealloc" title="Permalink to this definition">¶</a></dt>
<dd><p>A pointer to the instance destructor function. This function must be defined
unless the type guarantees that its instances will never be deallocated (as is
the case for the singletons <tt class="xref docutils literal"><span class="pre">None</span></tt> and <tt class="docutils literal"><span class="pre">Ellipsis</span></tt>).</p>
<p>The destructor function is called by the <a class="reference internal" href="refcounting.html#Py_DECREF" title="Py_DECREF"><tt class="xref c c-func docutils literal"><span class="pre">Py_DECREF()</span></tt></a> and
<a class="reference internal" href="refcounting.html#Py_XDECREF" title="Py_XDECREF"><tt class="xref c c-func docutils literal"><span class="pre">Py_XDECREF()</span></tt></a> macros when the new reference count is zero. At this point,
the instance is still in existence, but there are no references to it. The
destructor function should free all references which the instance owns, free all
memory buffers owned by the instance (using the freeing function corresponding
to the allocation function used to allocate the buffer), and finally (as its
last action) call the type’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_free</span></tt> function. If the type is not
subtypable (doesn’t have the <a class="reference internal" href="#Py_TPFLAGS_BASETYPE" title="Py_TPFLAGS_BASETYPE"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_BASETYPE</span></tt></a> flag bit set), it is
permissible to call the object deallocator directly instead of via
<tt class="xref py py-attr docutils literal"><span class="pre">tp_free</span></tt>. The object deallocator should be the one used to allocate the
instance; this is normally <a class="reference internal" href="allocation.html#PyObject_Del" title="PyObject_Del"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Del()</span></tt></a> if the instance was allocated
using <a class="reference internal" href="allocation.html#PyObject_New" title="PyObject_New"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_New()</span></tt></a> or <tt class="xref c c-func docutils literal"><span class="pre">PyObject_VarNew()</span></tt>, or
<a class="reference internal" href="gcsupport.html#PyObject_GC_Del" title="PyObject_GC_Del"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GC_Del()</span></tt></a> if the instance was allocated using
<a class="reference internal" href="gcsupport.html#PyObject_GC_New" title="PyObject_GC_New"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GC_New()</span></tt></a> or <a class="reference internal" href="gcsupport.html#PyObject_GC_NewVar" title="PyObject_GC_NewVar"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GC_NewVar()</span></tt></a>.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_print">
printfunc <tt class="descname">PyTypeObject.tp_print</tt><a class="headerlink" href="#PyTypeObject.tp_print" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to the instance print function.</p>
<p>The print function is only called when the instance is printed to a <em>real</em> file;
when it is printed to a pseudo-file (like a <tt class="xref py py-class docutils literal"><span class="pre">StringIO</span></tt> instance), the
instance’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_repr</span></tt> or <tt class="xref py py-attr docutils literal"><span class="pre">tp_str</span></tt> function is called to convert it to
a string. These are also called when the type’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_print</span></tt> field is
<em>NULL</em>. A type should never implement <tt class="xref py py-attr docutils literal"><span class="pre">tp_print</span></tt> in a way that produces
different output than <tt class="xref py py-attr docutils literal"><span class="pre">tp_repr</span></tt> or <tt class="xref py py-attr docutils literal"><span class="pre">tp_str</span></tt> would.</p>
<p>The print function is called with the same signature as <a class="reference internal" href="object.html#PyObject_Print" title="PyObject_Print"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Print()</span></tt></a>:
<tt class="docutils literal"><span class="pre">int</span> <span class="pre">tp_print(PyObject</span> <span class="pre">*self,</span> <span class="pre">FILE</span> <span class="pre">*file,</span> <span class="pre">int</span> <span class="pre">flags)</span></tt>. The <em>self</em> argument is
the instance to be printed. The <em>file</em> argument is the stdio file to which it
is to be printed. The <em>flags</em> argument is composed of flag bits. The only flag
bit currently defined is <tt class="xref py py-const docutils literal"><span class="pre">Py_PRINT_RAW</span></tt>. When the <tt class="xref py py-const docutils literal"><span class="pre">Py_PRINT_RAW</span></tt>
flag bit is set, the instance should be printed the same way as <tt class="xref py py-attr docutils literal"><span class="pre">tp_str</span></tt>
would format it; when the <tt class="xref py py-const docutils literal"><span class="pre">Py_PRINT_RAW</span></tt> flag bit is clear, the instance
should be printed the same was as <tt class="xref py py-attr docutils literal"><span class="pre">tp_repr</span></tt> would format it. It should
return <tt class="docutils literal"><span class="pre">-1</span></tt> and set an exception condition when an error occurred during the
comparison.</p>
<p>It is possible that the <tt class="xref py py-attr docutils literal"><span class="pre">tp_print</span></tt> field will be deprecated. In any case,
it is recommended not to define <tt class="xref py py-attr docutils literal"><span class="pre">tp_print</span></tt>, but instead to rely on
<tt class="xref py py-attr docutils literal"><span class="pre">tp_repr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_str</span></tt> for printing.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_getattr">
getattrfunc <tt class="descname">PyTypeObject.tp_getattr</tt><a class="headerlink" href="#PyTypeObject.tp_getattr" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to the get-attribute-string function.</p>
<p>This field is deprecated. When it is defined, it should point to a function
that acts the same as the <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt> function, but taking a C string
instead of a Python string object to give the attribute name. The signature is
the same as for <a class="reference internal" href="object.html#PyObject_GetAttrString" title="PyObject_GetAttrString"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GetAttrString()</span></tt></a>.</p>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt>: a subtype
inherits both <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt> from its base type when
the subtype’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt> are both <em>NULL</em>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_setattr">
setattrfunc <tt class="descname">PyTypeObject.tp_setattr</tt><a class="headerlink" href="#PyTypeObject.tp_setattr" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to the set-attribute-string function.</p>
<p>This field is deprecated. When it is defined, it should point to a function
that acts the same as the <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattro</span></tt> function, but taking a C string
instead of a Python string object to give the attribute name. The signature is
the same as for <a class="reference internal" href="object.html#PyObject_SetAttrString" title="PyObject_SetAttrString"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_SetAttrString()</span></tt></a>.</p>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattro</span></tt>: a subtype
inherits both <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattro</span></tt> from its base type when
the subtype’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattro</span></tt> are both <em>NULL</em>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_reserved">
void* <tt class="descname">PyTypeObject.tp_reserved</tt><a class="headerlink" href="#PyTypeObject.tp_reserved" title="Permalink to this definition">¶</a></dt>
<dd><p>Reserved slot, formerly known as tp_compare.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_repr">
reprfunc <tt class="descname">PyTypeObject.tp_repr</tt><a class="headerlink" href="#PyTypeObject.tp_repr" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-1">An optional pointer to a function that implements the built-in function
<a class="reference internal" href="../library/functions.html#repr" title="repr"><tt class="xref py py-func docutils literal"><span class="pre">repr()</span></tt></a>.</p>
<p>The signature is the same as for <a class="reference internal" href="object.html#PyObject_Repr" title="PyObject_Repr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Repr()</span></tt></a>; it must return a string
or a Unicode object. Ideally, this function should return a string that, when
passed to <a class="reference internal" href="../library/functions.html#eval" title="eval"><tt class="xref py py-func docutils literal"><span class="pre">eval()</span></tt></a>, given a suitable environment, returns an object with the
same value. If this is not feasible, it should return a string starting with
<tt class="docutils literal"><span class="pre">'<'</span></tt> and ending with <tt class="docutils literal"><span class="pre">'>'</span></tt> from which both the type and the value of the
object can be deduced.</p>
<p>When this field is not set, a string of the form <tt class="docutils literal"><span class="pre"><%s</span> <span class="pre">object</span> <span class="pre">at</span> <span class="pre">%p></span></tt> is
returned, where <tt class="docutils literal"><span class="pre">%s</span></tt> is replaced by the type name, and <tt class="docutils literal"><span class="pre">%p</span></tt> by the object’s
memory address.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="tp_as_number">
<a class="reference internal" href="#PyNumberMethods" title="PyNumberMethods">PyNumberMethods</a>* <tt class="descname">tp_as_number</tt><a class="headerlink" href="#tp_as_number" title="Permalink to this definition">¶</a></dt>
<dd><p>Pointer to an additional structure that contains fields relevant only to
objects which implement the number protocol. These fields are documented in
<a class="reference internal" href="#number-structs"><em>Number Object Structures</em></a>.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_number</span></tt> field is not inherited, but the contained fields are
inherited individually.</p>
</dd></dl>
<dl class="member">
<dt id="tp_as_sequence">
<a class="reference internal" href="#PySequenceMethods" title="PySequenceMethods">PySequenceMethods</a>* <tt class="descname">tp_as_sequence</tt><a class="headerlink" href="#tp_as_sequence" title="Permalink to this definition">¶</a></dt>
<dd><p>Pointer to an additional structure that contains fields relevant only to
objects which implement the sequence protocol. These fields are documented
in <a class="reference internal" href="#sequence-structs"><em>Sequence Object Structures</em></a>.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_sequence</span></tt> field is not inherited, but the contained fields
are inherited individually.</p>
</dd></dl>
<dl class="member">
<dt id="tp_as_mapping">
<a class="reference internal" href="#PyMappingMethods" title="PyMappingMethods">PyMappingMethods</a>* <tt class="descname">tp_as_mapping</tt><a class="headerlink" href="#tp_as_mapping" title="Permalink to this definition">¶</a></dt>
<dd><p>Pointer to an additional structure that contains fields relevant only to
objects which implement the mapping protocol. These fields are documented in
<a class="reference internal" href="#mapping-structs"><em>Mapping Object Structures</em></a>.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_mapping</span></tt> field is not inherited, but the contained fields
are inherited individually.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_hash">
hashfunc <tt class="descname">PyTypeObject.tp_hash</tt><a class="headerlink" href="#PyTypeObject.tp_hash" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-2">An optional pointer to a function that implements the built-in function
<a class="reference internal" href="../library/functions.html#hash" title="hash"><tt class="xref py py-func docutils literal"><span class="pre">hash()</span></tt></a>.</p>
<p>The signature is the same as for <a class="reference internal" href="object.html#PyObject_Hash" title="PyObject_Hash"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Hash()</span></tt></a>; it must return a
value of the type Py_hash_t. The value <tt class="docutils literal"><span class="pre">-1</span></tt> should not be returned as a
normal return value; when an error occurs during the computation of the hash
value, the function should set an exception and return <tt class="docutils literal"><span class="pre">-1</span></tt>.</p>
<p>This field can be set explicitly to <a class="reference internal" href="object.html#PyObject_HashNotImplemented" title="PyObject_HashNotImplemented"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_HashNotImplemented()</span></tt></a> to
block inheritance of the hash method from a parent type. This is interpreted
as the equivalent of <tt class="docutils literal"><span class="pre">__hash__</span> <span class="pre">=</span> <span class="pre">None</span></tt> at the Python level, causing
<tt class="docutils literal"><span class="pre">isinstance(o,</span> <span class="pre">collections.Hashable)</span></tt> to correctly return <tt class="xref docutils literal"><span class="pre">False</span></tt>. Note
that the converse is also true - setting <tt class="docutils literal"><span class="pre">__hash__</span> <span class="pre">=</span> <span class="pre">None</span></tt> on a class at
the Python level will result in the <tt class="docutils literal"><span class="pre">tp_hash</span></tt> slot being set to
<a class="reference internal" href="object.html#PyObject_HashNotImplemented" title="PyObject_HashNotImplemented"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_HashNotImplemented()</span></tt></a>.</p>
<p>When this field is not set, an attempt to take the hash of the
object raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><tt class="xref py py-exc docutils literal"><span class="pre">TypeError</span></tt></a>.</p>
<p>This field is inherited by subtypes together with
<tt class="xref py py-attr docutils literal"><span class="pre">tp_richcompare</span></tt>: a subtype inherits both of
<tt class="xref py py-attr docutils literal"><span class="pre">tp_richcompare</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_hash</span></tt>, when the subtype’s
<tt class="xref py py-attr docutils literal"><span class="pre">tp_richcompare</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_hash</span></tt> are both <em>NULL</em>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_call">
ternaryfunc <tt class="descname">PyTypeObject.tp_call</tt><a class="headerlink" href="#PyTypeObject.tp_call" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a function that implements calling the object. This
should be <em>NULL</em> if the object is not callable. The signature is the same as
for <a class="reference internal" href="object.html#PyObject_Call" title="PyObject_Call"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Call()</span></tt></a>.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_str">
reprfunc <tt class="descname">PyTypeObject.tp_str</tt><a class="headerlink" href="#PyTypeObject.tp_str" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a function that implements the built-in operation
<a class="reference internal" href="../library/functions.html#str" title="str"><tt class="xref py py-func docutils literal"><span class="pre">str()</span></tt></a>. (Note that <a class="reference internal" href="../library/functions.html#str" title="str"><tt class="xref py py-class docutils literal"><span class="pre">str</span></tt></a> is a type now, and <a class="reference internal" href="../library/functions.html#str" title="str"><tt class="xref py py-func docutils literal"><span class="pre">str()</span></tt></a> calls the
constructor for that type. This constructor calls <a class="reference internal" href="object.html#PyObject_Str" title="PyObject_Str"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Str()</span></tt></a> to do
the actual work, and <a class="reference internal" href="object.html#PyObject_Str" title="PyObject_Str"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Str()</span></tt></a> will call this handler.)</p>
<p>The signature is the same as for <a class="reference internal" href="object.html#PyObject_Str" title="PyObject_Str"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Str()</span></tt></a>; it must return a string
or a Unicode object. This function should return a “friendly” string
representation of the object, as this is the representation that will be used,
among other things, by the <a class="reference internal" href="../library/functions.html#print" title="print"><tt class="xref py py-func docutils literal"><span class="pre">print()</span></tt></a> function.</p>
<p>When this field is not set, <a class="reference internal" href="object.html#PyObject_Repr" title="PyObject_Repr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Repr()</span></tt></a> is called to return a string
representation.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_getattro">
getattrofunc <tt class="descname">PyTypeObject.tp_getattro</tt><a class="headerlink" href="#PyTypeObject.tp_getattro" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to the get-attribute function.</p>
<p>The signature is the same as for <a class="reference internal" href="object.html#PyObject_GetAttr" title="PyObject_GetAttr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GetAttr()</span></tt></a>. It is usually
convenient to set this field to <a class="reference internal" href="object.html#PyObject_GenericGetAttr" title="PyObject_GenericGetAttr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GenericGetAttr()</span></tt></a>, which
implements the normal way of looking for object attributes.</p>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattr</span></tt>: a subtype
inherits both <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt> from its base type when
the subtype’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_getattro</span></tt> are both <em>NULL</em>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_setattro">
setattrofunc <tt class="descname">PyTypeObject.tp_setattro</tt><a class="headerlink" href="#PyTypeObject.tp_setattro" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to the set-attribute function.</p>
<p>The signature is the same as for <a class="reference internal" href="object.html#PyObject_SetAttr" title="PyObject_SetAttr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_SetAttr()</span></tt></a>. It is usually
convenient to set this field to <a class="reference internal" href="object.html#PyObject_GenericSetAttr" title="PyObject_GenericSetAttr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GenericSetAttr()</span></tt></a>, which
implements the normal way of setting object attributes.</p>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattr</span></tt>: a subtype
inherits both <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattro</span></tt> from its base type when
the subtype’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattr</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_setattro</span></tt> are both <em>NULL</em>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_as_buffer">
<a class="reference internal" href="#PyBufferProcs" title="PyBufferProcs">PyBufferProcs</a>* <tt class="descname">PyTypeObject.tp_as_buffer</tt><a class="headerlink" href="#PyTypeObject.tp_as_buffer" title="Permalink to this definition">¶</a></dt>
<dd><p>Pointer to an additional structure that contains fields relevant only to objects
which implement the buffer interface. These fields are documented in
<a class="reference internal" href="#buffer-structs"><em>Buffer Object Structures</em></a>.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_buffer</span></tt> field is not inherited, but the contained fields are
inherited individually.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_flags">
long <tt class="descname">PyTypeObject.tp_flags</tt><a class="headerlink" href="#PyTypeObject.tp_flags" title="Permalink to this definition">¶</a></dt>
<dd><p>This field is a bit mask of various flags. Some flags indicate variant
semantics for certain situations; others are used to indicate that certain
fields in the type object (or in the extension structures referenced via
<tt class="xref py py-attr docutils literal"><span class="pre">tp_as_number</span></tt>, <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_sequence</span></tt>, <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_mapping</span></tt>, and
<tt class="xref py py-attr docutils literal"><span class="pre">tp_as_buffer</span></tt>) that were historically not always present are valid; if
such a flag bit is clear, the type fields it guards must not be accessed and
must be considered to have a zero or <em>NULL</em> value instead.</p>
<p>Inheritance of this field is complicated. Most flag bits are inherited
individually, i.e. if the base type has a flag bit set, the subtype inherits
this flag bit. The flag bits that pertain to extension structures are strictly
inherited if the extension structure is inherited, i.e. the base type’s value of
the flag bit is copied into the subtype together with a pointer to the extension
structure. The <a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit is inherited together with
the <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> fields, i.e. if the
<a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit is clear in the subtype and the
<tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> fields in the subtype exist and have
<em>NULL</em> values.</p>
<p>The following bit masks are currently defined; these can be ORed together using
the <tt class="docutils literal"><span class="pre">|</span></tt> operator to form the value of the <tt class="xref py py-attr docutils literal"><span class="pre">tp_flags</span></tt> field. The macro
<a class="reference internal" href="type.html#PyType_HasFeature" title="PyType_HasFeature"><tt class="xref c c-func docutils literal"><span class="pre">PyType_HasFeature()</span></tt></a> takes a type and a flags value, <em>tp</em> and <em>f</em>, and
checks whether <tt class="docutils literal"><span class="pre">tp->tp_flags</span> <span class="pre">&</span> <span class="pre">f</span></tt> is non-zero.</p>
<dl class="data">
<dt id="Py_TPFLAGS_HEAPTYPE">
<tt class="descname">Py_TPFLAGS_HEAPTYPE</tt><a class="headerlink" href="#Py_TPFLAGS_HEAPTYPE" title="Permalink to this definition">¶</a></dt>
<dd><p>This bit is set when the type object itself is allocated on the heap. In this
case, the <tt class="xref py py-attr docutils literal"><span class="pre">ob_type</span></tt> field of its instances is considered a reference to
the type, and the type object is INCREF’ed when a new instance is created, and
DECREF’ed when an instance is destroyed (this does not apply to instances of
subtypes; only the type referenced by the instance’s ob_type gets INCREF’ed or
DECREF’ed).</p>
</dd></dl>
<dl class="data">
<dt id="Py_TPFLAGS_BASETYPE">
<tt class="descname">Py_TPFLAGS_BASETYPE</tt><a class="headerlink" href="#Py_TPFLAGS_BASETYPE" title="Permalink to this definition">¶</a></dt>
<dd><p>This bit is set when the type can be used as the base type of another type. If
this bit is clear, the type cannot be subtyped (similar to a “final” class in
Java).</p>
</dd></dl>
<dl class="data">
<dt id="Py_TPFLAGS_READY">
<tt class="descname">Py_TPFLAGS_READY</tt><a class="headerlink" href="#Py_TPFLAGS_READY" title="Permalink to this definition">¶</a></dt>
<dd><p>This bit is set when the type object has been fully initialized by
<a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a>.</p>
</dd></dl>
<dl class="data">
<dt id="Py_TPFLAGS_READYING">
<tt class="descname">Py_TPFLAGS_READYING</tt><a class="headerlink" href="#Py_TPFLAGS_READYING" title="Permalink to this definition">¶</a></dt>
<dd><p>This bit is set while <a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a> is in the process of initializing
the type object.</p>
</dd></dl>
<dl class="data">
<dt id="Py_TPFLAGS_HAVE_GC">
<tt class="descname">Py_TPFLAGS_HAVE_GC</tt><a class="headerlink" href="#Py_TPFLAGS_HAVE_GC" title="Permalink to this definition">¶</a></dt>
<dd><p>This bit is set when the object supports garbage collection. If this bit
is set, instances must be created using <a class="reference internal" href="gcsupport.html#PyObject_GC_New" title="PyObject_GC_New"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GC_New()</span></tt></a> and
destroyed using <a class="reference internal" href="gcsupport.html#PyObject_GC_Del" title="PyObject_GC_Del"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GC_Del()</span></tt></a>. More information in section
<a class="reference internal" href="gcsupport.html#supporting-cycle-detection"><em>Supporting Cyclic Garbage Collection</em></a>. This bit also implies that the
GC-related fields <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> are present in
the type object.</p>
</dd></dl>
<dl class="data">
<dt id="Py_TPFLAGS_DEFAULT">
<tt class="descname">Py_TPFLAGS_DEFAULT</tt><a class="headerlink" href="#Py_TPFLAGS_DEFAULT" title="Permalink to this definition">¶</a></dt>
<dd><p>This is a bitmask of all the bits that pertain to the existence of certain
fields in the type object and its extension structures. Currently, it includes
the following bits: <tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_STACKLESS_EXTENSION</span></tt>,
<tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_VERSION_TAG</span></tt>.</p>
</dd></dl>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_doc">
char* <tt class="descname">PyTypeObject.tp_doc</tt><a class="headerlink" href="#PyTypeObject.tp_doc" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a NUL-terminated C string giving the docstring for this
type object. This is exposed as the <tt class="xref py py-attr docutils literal"><span class="pre">__doc__</span></tt> attribute on the type and
instances of the type.</p>
<p>This field is <em>not</em> inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_traverse">
<a class="reference internal" href="gcsupport.html#traverseproc" title="traverseproc">traverseproc</a> <tt class="descname">PyTypeObject.tp_traverse</tt><a class="headerlink" href="#PyTypeObject.tp_traverse" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a traversal function for the garbage collector. This is
only used if the <a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit is set. More information
about Python’s garbage collection scheme can be found in section
<a class="reference internal" href="gcsupport.html#supporting-cycle-detection"><em>Supporting Cyclic Garbage Collection</em></a>.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt> pointer is used by the garbage collector to detect
reference cycles. A typical implementation of a <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt> function
simply calls <a class="reference internal" href="gcsupport.html#Py_VISIT" title="Py_VISIT"><tt class="xref c c-func docutils literal"><span class="pre">Py_VISIT()</span></tt></a> on each of the instance’s members that are Python
objects. For example, this is function <tt class="xref c c-func docutils literal"><span class="pre">local_traverse()</span></tt> from the
<a class="reference internal" href="../library/_thread.html#module-_thread" title="_thread: Low-level threading API."><tt class="xref py py-mod docutils literal"><span class="pre">_thread</span></tt></a> extension module:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="k">static</span> <span class="kt">int</span>
<span class="nf">local_traverse</span><span class="p">(</span><span class="n">localobject</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">visitproc</span> <span class="n">visit</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="n">arg</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">Py_VISIT</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">args</span><span class="p">);</span>
<span class="n">Py_VISIT</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">kw</span><span class="p">);</span>
<span class="n">Py_VISIT</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">dict</span><span class="p">);</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Note that <a class="reference internal" href="gcsupport.html#Py_VISIT" title="Py_VISIT"><tt class="xref c c-func docutils literal"><span class="pre">Py_VISIT()</span></tt></a> is called only on those members that can participate
in reference cycles. Although there is also a <tt class="docutils literal"><span class="pre">self->key</span></tt> member, it can only
be <em>NULL</em> or a Python string and therefore cannot be part of a reference cycle.</p>
<p>On the other hand, even if you know a member can never be part of a cycle, as a
debugging aid you may want to visit it anyway just so the <a class="reference internal" href="../library/gc.html#module-gc" title="gc: Interface to the cycle-detecting garbage collector."><tt class="xref py py-mod docutils literal"><span class="pre">gc</span></tt></a> module’s
<tt class="xref py py-func docutils literal"><span class="pre">get_referents()</span></tt> function will include it.</p>
<p>Note that <a class="reference internal" href="gcsupport.html#Py_VISIT" title="Py_VISIT"><tt class="xref c c-func docutils literal"><span class="pre">Py_VISIT()</span></tt></a> requires the <em>visit</em> and <em>arg</em> parameters to
<tt class="xref c c-func docutils literal"><span class="pre">local_traverse()</span></tt> to have these specific names; don’t name them just
anything.</p>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> and the
<a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit: the flag bit, <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt>, and
<tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> are all inherited from the base type if they are all zero in
the subtype.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_clear">
<a class="reference internal" href="gcsupport.html#inquiry" title="inquiry">inquiry</a> <tt class="descname">PyTypeObject.tp_clear</tt><a class="headerlink" href="#PyTypeObject.tp_clear" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a clear function for the garbage collector. This is only
used if the <a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit is set.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> member function is used to break reference cycles in cyclic
garbage detected by the garbage collector. Taken together, all <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt>
functions in the system must combine to break all reference cycles. This is
subtle, and if in any doubt supply a <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> function. For example,
the tuple type does not implement a <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> function, because it’s
possible to prove that no reference cycle can be composed entirely of tuples.
Therefore the <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> functions of other types must be sufficient to
break any cycle containing a tuple. This isn’t immediately obvious, and there’s
rarely a good reason to avoid implementing <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt>.</p>
<p>Implementations of <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> should drop the instance’s references to
those of its members that may be Python objects, and set its pointers to those
members to <em>NULL</em>, as in the following example:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="k">static</span> <span class="kt">int</span>
<span class="nf">local_clear</span><span class="p">(</span><span class="n">localobject</span> <span class="o">*</span><span class="n">self</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">Py_CLEAR</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">key</span><span class="p">);</span>
<span class="n">Py_CLEAR</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">args</span><span class="p">);</span>
<span class="n">Py_CLEAR</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">kw</span><span class="p">);</span>
<span class="n">Py_CLEAR</span><span class="p">(</span><span class="n">self</span><span class="o">-></span><span class="n">dict</span><span class="p">);</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>The <a class="reference internal" href="refcounting.html#Py_CLEAR" title="Py_CLEAR"><tt class="xref c c-func docutils literal"><span class="pre">Py_CLEAR()</span></tt></a> macro should be used, because clearing references is
delicate: the reference to the contained object must not be decremented until
after the pointer to the contained object is set to <em>NULL</em>. This is because
decrementing the reference count may cause the contained object to become trash,
triggering a chain of reclamation activity that may include invoking arbitrary
Python code (due to finalizers, or weakref callbacks, associated with the
contained object). If it’s possible for such code to reference <em>self</em> again,
it’s important that the pointer to the contained object be <em>NULL</em> at that time,
so that <em>self</em> knows the contained object can no longer be used. The
<a class="reference internal" href="refcounting.html#Py_CLEAR" title="Py_CLEAR"><tt class="xref c c-func docutils literal"><span class="pre">Py_CLEAR()</span></tt></a> macro performs the operations in a safe order.</p>
<p>Because the goal of <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> functions is to break reference cycles,
it’s not necessary to clear contained objects like Python strings or Python
integers, which can’t participate in reference cycles. On the other hand, it may
be convenient to clear all contained Python objects, and write the type’s
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dealloc</span></tt> function to invoke <tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt>.</p>
<p>More information about Python’s garbage collection scheme can be found in
section <a class="reference internal" href="gcsupport.html#supporting-cycle-detection"><em>Supporting Cyclic Garbage Collection</em></a>.</p>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt> and the
<a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit: the flag bit, <tt class="xref py py-attr docutils literal"><span class="pre">tp_traverse</span></tt>, and
<tt class="xref py py-attr docutils literal"><span class="pre">tp_clear</span></tt> are all inherited from the base type if they are all zero in
the subtype.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_richcompare">
richcmpfunc <tt class="descname">PyTypeObject.tp_richcompare</tt><a class="headerlink" href="#PyTypeObject.tp_richcompare" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to the rich comparison function, whose signature is
<tt class="docutils literal"><span class="pre">PyObject</span> <span class="pre">*tp_richcompare(PyObject</span> <span class="pre">*a,</span> <span class="pre">PyObject</span> <span class="pre">*b,</span> <span class="pre">int</span> <span class="pre">op)</span></tt>.</p>
<p>The function should return the result of the comparison (usually <tt class="docutils literal"><span class="pre">Py_True</span></tt>
or <tt class="docutils literal"><span class="pre">Py_False</span></tt>). If the comparison is undefined, it must return
<tt class="docutils literal"><span class="pre">Py_NotImplemented</span></tt>, if another error occurred it must return <tt class="docutils literal"><span class="pre">NULL</span></tt> and
set an exception condition.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If you want to implement a type for which only a limited set of
comparisons makes sense (e.g. <tt class="docutils literal"><span class="pre">==</span></tt> and <tt class="docutils literal"><span class="pre">!=</span></tt>, but not <tt class="docutils literal"><span class="pre"><</span></tt> and
friends), directly raise <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><tt class="xref py py-exc docutils literal"><span class="pre">TypeError</span></tt></a> in the rich comparison function.</p>
</div>
<p>This field is inherited by subtypes together with <tt class="xref py py-attr docutils literal"><span class="pre">tp_hash</span></tt>:
a subtype inherits <tt class="xref py py-attr docutils literal"><span class="pre">tp_richcompare</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_hash</span></tt> when
the subtype’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_richcompare</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_hash</span></tt> are both
<em>NULL</em>.</p>
<p>The following constants are defined to be used as the third argument for
<tt class="xref py py-attr docutils literal"><span class="pre">tp_richcompare</span></tt> and for <a class="reference internal" href="object.html#PyObject_RichCompare" title="PyObject_RichCompare"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_RichCompare()</span></tt></a>:</p>
<table border="1" class="docutils">
<colgroup>
<col width="57%" />
<col width="43%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Constant</th>
<th class="head">Comparison</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="xref py py-const docutils literal"><span class="pre">Py_LT</span></tt></td>
<td><tt class="docutils literal"><span class="pre"><</span></tt></td>
</tr>
<tr><td><tt class="xref py py-const docutils literal"><span class="pre">Py_LE</span></tt></td>
<td><tt class="docutils literal"><span class="pre"><=</span></tt></td>
</tr>
<tr><td><tt class="xref py py-const docutils literal"><span class="pre">Py_EQ</span></tt></td>
<td><tt class="docutils literal"><span class="pre">==</span></tt></td>
</tr>
<tr><td><tt class="xref py py-const docutils literal"><span class="pre">Py_NE</span></tt></td>
<td><tt class="docutils literal"><span class="pre">!=</span></tt></td>
</tr>
<tr><td><tt class="xref py py-const docutils literal"><span class="pre">Py_GT</span></tt></td>
<td><tt class="docutils literal"><span class="pre">></span></tt></td>
</tr>
<tr><td><tt class="xref py py-const docutils literal"><span class="pre">Py_GE</span></tt></td>
<td><tt class="docutils literal"><span class="pre">>=</span></tt></td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_weaklistoffset">
long <tt class="descname">PyTypeObject.tp_weaklistoffset</tt><a class="headerlink" href="#PyTypeObject.tp_weaklistoffset" title="Permalink to this definition">¶</a></dt>
<dd><p>If the instances of this type are weakly referenceable, this field is greater
than zero and contains the offset in the instance structure of the weak
reference list head (ignoring the GC header, if present); this offset is used by
<tt class="xref c c-func docutils literal"><span class="pre">PyObject_ClearWeakRefs()</span></tt> and the <tt class="xref c c-func docutils literal"><span class="pre">PyWeakref_*()</span></tt> functions. The
instance structure needs to include a field of type <a class="reference internal" href="structures.html#PyObject" title="PyObject"><tt class="xref c c-type docutils literal"><span class="pre">PyObject*</span></tt></a> which is
initialized to <em>NULL</em>.</p>
<p>Do not confuse this field with <tt class="xref py py-attr docutils literal"><span class="pre">tp_weaklist</span></tt>; that is the list head for
weak references to the type object itself.</p>
<p>This field is inherited by subtypes, but see the rules listed below. A subtype
may override this offset; this means that the subtype uses a different weak
reference list head than the base type. Since the list head is always found via
<tt class="xref py py-attr docutils literal"><span class="pre">tp_weaklistoffset</span></tt>, this should not be a problem.</p>
<p>When a type defined by a class statement has no <tt class="xref py py-attr docutils literal"><span class="pre">__slots__</span></tt> declaration,
and none of its base types are weakly referenceable, the type is made weakly
referenceable by adding a weak reference list head slot to the instance layout
and setting the <tt class="xref py py-attr docutils literal"><span class="pre">tp_weaklistoffset</span></tt> of that slot’s offset.</p>
<p>When a type’s <tt class="xref py py-attr docutils literal"><span class="pre">__slots__</span></tt> declaration contains a slot named
<tt class="xref py py-attr docutils literal"><span class="pre">__weakref__</span></tt>, that slot becomes the weak reference list head for
instances of the type, and the slot’s offset is stored in the type’s
<tt class="xref py py-attr docutils literal"><span class="pre">tp_weaklistoffset</span></tt>.</p>
<p>When a type’s <tt class="xref py py-attr docutils literal"><span class="pre">__slots__</span></tt> declaration does not contain a slot named
<tt class="xref py py-attr docutils literal"><span class="pre">__weakref__</span></tt>, the type inherits its <tt class="xref py py-attr docutils literal"><span class="pre">tp_weaklistoffset</span></tt> from its
base type.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_iter">
getiterfunc <tt class="descname">PyTypeObject.tp_iter</tt><a class="headerlink" href="#PyTypeObject.tp_iter" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a function that returns an iterator for the object. Its
presence normally signals that the instances of this type are iterable (although
sequences may be iterable without this function).</p>
<p>This function has the same signature as <a class="reference internal" href="object.html#PyObject_GetIter" title="PyObject_GetIter"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GetIter()</span></tt></a>.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_iternext">
iternextfunc <tt class="descname">PyTypeObject.tp_iternext</tt><a class="headerlink" href="#PyTypeObject.tp_iternext" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a function that returns the next item in an iterator.
When the iterator is exhausted, it must return <em>NULL</em>; a <a class="reference internal" href="../library/exceptions.html#StopIteration" title="StopIteration"><tt class="xref py py-exc docutils literal"><span class="pre">StopIteration</span></tt></a>
exception may or may not be set. When another error occurs, it must return
<em>NULL</em> too. Its presence signals that the instances of this type are
iterators.</p>
<p>Iterator types should also define the <tt class="xref py py-attr docutils literal"><span class="pre">tp_iter</span></tt> function, and that
function should return the iterator instance itself (not a new iterator
instance).</p>
<p>This function has the same signature as <a class="reference internal" href="iter.html#PyIter_Next" title="PyIter_Next"><tt class="xref c c-func docutils literal"><span class="pre">PyIter_Next()</span></tt></a>.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_methods">
struct <a class="reference internal" href="structures.html#PyMethodDef" title="PyMethodDef">PyMethodDef</a>* <tt class="descname">PyTypeObject.tp_methods</tt><a class="headerlink" href="#PyTypeObject.tp_methods" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a static <em>NULL</em>-terminated array of <a class="reference internal" href="structures.html#PyMethodDef" title="PyMethodDef"><tt class="xref c c-type docutils literal"><span class="pre">PyMethodDef</span></tt></a>
structures, declaring regular methods of this type.</p>
<p>For each entry in the array, an entry is added to the type’s dictionary (see
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dict</span></tt> below) containing a method descriptor.</p>
<p>This field is not inherited by subtypes (methods are inherited through a
different mechanism).</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_members">
struct <a class="reference internal" href="structures.html#PyMemberDef" title="PyMemberDef">PyMemberDef</a>* <tt class="descname">PyTypeObject.tp_members</tt><a class="headerlink" href="#PyTypeObject.tp_members" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a static <em>NULL</em>-terminated array of <a class="reference internal" href="structures.html#PyMemberDef" title="PyMemberDef"><tt class="xref c c-type docutils literal"><span class="pre">PyMemberDef</span></tt></a>
structures, declaring regular data members (fields or slots) of instances of
this type.</p>
<p>For each entry in the array, an entry is added to the type’s dictionary (see
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dict</span></tt> below) containing a member descriptor.</p>
<p>This field is not inherited by subtypes (members are inherited through a
different mechanism).</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_getset">
struct PyGetSetDef* <tt class="descname">PyTypeObject.tp_getset</tt><a class="headerlink" href="#PyTypeObject.tp_getset" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a static <em>NULL</em>-terminated array of <tt class="xref c c-type docutils literal"><span class="pre">PyGetSetDef</span></tt>
structures, declaring computed attributes of instances of this type.</p>
<p>For each entry in the array, an entry is added to the type’s dictionary (see
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dict</span></tt> below) containing a getset descriptor.</p>
<p>This field is not inherited by subtypes (computed attributes are inherited
through a different mechanism).</p>
<p>Docs for PyGetSetDef:</p>
<div class="highlight-c"><div class="highlight"><pre><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>
<span class="k">typedef</span> <span class="kt">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>
<span class="k">typedef</span> <span class="k">struct</span> <span class="n">PyGetSetDef</span> <span class="p">{</span>
<span class="kt">char</span> <span class="o">*</span><span class="n">name</span><span class="p">;</span> <span class="cm">/* attribute name */</span>
<span class="n">getter</span> <span class="n">get</span><span class="p">;</span> <span class="cm">/* C function to get the attribute */</span>
<span class="n">setter</span> <span class="n">set</span><span class="p">;</span> <span class="cm">/* C function to set the attribute */</span>
<span class="kt">char</span> <span class="o">*</span><span class="n">doc</span><span class="p">;</span> <span class="cm">/* optional doc string */</span>
<span class="kt">void</span> <span class="o">*</span><span class="n">closure</span><span class="p">;</span> <span class="cm">/* optional additional data for getter and setter */</span>
<span class="p">}</span> <span class="n">PyGetSetDef</span><span class="p">;</span>
</pre></div>
</div>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_base">
<a class="reference internal" href="type.html#PyTypeObject" title="PyTypeObject">PyTypeObject</a>* <tt class="descname">PyTypeObject.tp_base</tt><a class="headerlink" href="#PyTypeObject.tp_base" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a base type from which type properties are inherited. At
this level, only single inheritance is supported; multiple inheritance require
dynamically creating a type object by calling the metatype.</p>
<p>This field is not inherited by subtypes (obviously), but it defaults to
<tt class="docutils literal"><span class="pre">&PyBaseObject_Type</span></tt> (which to Python programmers is known as the type
<a class="reference internal" href="../library/functions.html#object" title="object"><tt class="xref py py-class docutils literal"><span class="pre">object</span></tt></a>).</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_dict">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyTypeObject.tp_dict</tt><a class="headerlink" href="#PyTypeObject.tp_dict" title="Permalink to this definition">¶</a></dt>
<dd><p>The type’s dictionary is stored here by <a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a>.</p>
<p>This field should normally be initialized to <em>NULL</em> before PyType_Ready is
called; it may also be initialized to a dictionary containing initial attributes
for the type. Once <a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a> has initialized the type, extra
attributes for the type may be added to this dictionary only if they don’t
correspond to overloaded operations (like <a class="reference internal" href="../reference/datamodel.html#object.__add__" title="object.__add__"><tt class="xref py py-meth docutils literal"><span class="pre">__add__()</span></tt></a>).</p>
<p>This field is not inherited by subtypes (though the attributes defined in here
are inherited through a different mechanism).</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">It is not safe to use <a class="reference internal" href="dict.html#PyDict_SetItem" title="PyDict_SetItem"><tt class="xref c c-func docutils literal"><span class="pre">PyDict_SetItem()</span></tt></a> on or otherwise modify
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dict</span></tt> with the dictionary C-API.</p>
</div>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_descr_get">
descrgetfunc <tt class="descname">PyTypeObject.tp_descr_get</tt><a class="headerlink" href="#PyTypeObject.tp_descr_get" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a “descriptor get” function.</p>
<p>The function signature is</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">PyObject</span> <span class="o">*</span> <span class="n">tp_descr_get</span><span class="p">(</span><span class="n">PyObject</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">obj</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">type</span><span class="p">);</span>
</pre></div>
</div>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_descr_set">
descrsetfunc <tt class="descname">PyTypeObject.tp_descr_set</tt><a class="headerlink" href="#PyTypeObject.tp_descr_set" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a “descriptor set” function.</p>
<p>The function signature is</p>
<div class="highlight-c"><div class="highlight"><pre><span class="kt">int</span> <span class="n">tp_descr_set</span><span class="p">(</span><span class="n">PyObject</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">obj</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">value</span><span class="p">);</span>
</pre></div>
</div>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_dictoffset">
long <tt class="descname">PyTypeObject.tp_dictoffset</tt><a class="headerlink" href="#PyTypeObject.tp_dictoffset" title="Permalink to this definition">¶</a></dt>
<dd><p>If the instances of this type have a dictionary containing instance variables,
this field is non-zero and contains the offset in the instances of the type of
the instance variable dictionary; this offset is used by
<a class="reference internal" href="object.html#PyObject_GenericGetAttr" title="PyObject_GenericGetAttr"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GenericGetAttr()</span></tt></a>.</p>
<p>Do not confuse this field with <tt class="xref py py-attr docutils literal"><span class="pre">tp_dict</span></tt>; that is the dictionary for
attributes of the type object itself.</p>
<p>If the value of this field is greater than zero, it specifies the offset from
the start of the instance structure. If the value is less than zero, it
specifies the offset from the <em>end</em> of the instance structure. A negative
offset is more expensive to use, and should only be used when the instance
structure contains a variable-length part. This is used for example to add an
instance variable dictionary to subtypes of <a class="reference internal" href="../library/functions.html#str" title="str"><tt class="xref py py-class docutils literal"><span class="pre">str</span></tt></a> or <a class="reference internal" href="../library/functions.html#tuple" title="tuple"><tt class="xref py py-class docutils literal"><span class="pre">tuple</span></tt></a>. Note
that the <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt> field should account for the dictionary added to
the end in that case, even though the dictionary is not included in the basic
object layout. On a system with a pointer size of 4 bytes,
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dictoffset</span></tt> should be set to <tt class="docutils literal"><span class="pre">-4</span></tt> to indicate that the dictionary is
at the very end of the structure.</p>
<p>The real dictionary offset in an instance can be computed from a negative
<tt class="xref py py-attr docutils literal"><span class="pre">tp_dictoffset</span></tt> as follows:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">dictoffset</span> <span class="o">=</span> <span class="n">tp_basicsize</span> <span class="o">+</span> <span class="n">abs</span><span class="p">(</span><span class="n">ob_size</span><span class="p">)</span><span class="o">*</span><span class="n">tp_itemsize</span> <span class="o">+</span> <span class="n">tp_dictoffset</span>
<span class="k">if</span> <span class="n">dictoffset</span> <span class="n">is</span> <span class="n">not</span> <span class="n">aligned</span> <span class="n">on</span> <span class="k">sizeof</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span><span class="p">)</span><span class="o">:</span>
<span class="n">round</span> <span class="n">up</span> <span class="n">to</span> <span class="k">sizeof</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span><span class="p">)</span>
</pre></div>
</div>
<p>where <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt>, <tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tp_dictoffset</span></tt> are
taken from the type object, and <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> is taken from the instance. The
absolute value is taken because ints use the sign of <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> to
store the sign of the number. (There’s never a need to do this calculation
yourself; it is done for you by <tt class="xref c c-func docutils literal"><span class="pre">_PyObject_GetDictPtr()</span></tt>.)</p>
<p>This field is inherited by subtypes, but see the rules listed below. A subtype
may override this offset; this means that the subtype instances store the
dictionary at a difference offset than the base type. Since the dictionary is
always found via <tt class="xref py py-attr docutils literal"><span class="pre">tp_dictoffset</span></tt>, this should not be a problem.</p>
<p>When a type defined by a class statement has no <tt class="xref py py-attr docutils literal"><span class="pre">__slots__</span></tt> declaration,
and none of its base types has an instance variable dictionary, a dictionary
slot is added to the instance layout and the <tt class="xref py py-attr docutils literal"><span class="pre">tp_dictoffset</span></tt> is set to
that slot’s offset.</p>
<p>When a type defined by a class statement has a <tt class="xref py py-attr docutils literal"><span class="pre">__slots__</span></tt> declaration,
the type inherits its <tt class="xref py py-attr docutils literal"><span class="pre">tp_dictoffset</span></tt> from its base type.</p>
<p>(Adding a slot named <tt class="xref py py-attr docutils literal"><span class="pre">__dict__</span></tt> to the <tt class="xref py py-attr docutils literal"><span class="pre">__slots__</span></tt> declaration does
not have the expected effect, it just causes confusion. Maybe this should be
added as a feature just like <tt class="xref py py-attr docutils literal"><span class="pre">__weakref__</span></tt> though.)</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_init">
initproc <tt class="descname">PyTypeObject.tp_init</tt><a class="headerlink" href="#PyTypeObject.tp_init" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to an instance initialization function.</p>
<p>This function corresponds to the <a class="reference internal" href="../reference/datamodel.html#object.__init__" title="object.__init__"><tt class="xref py py-meth docutils literal"><span class="pre">__init__()</span></tt></a> method of classes. Like
<a class="reference internal" href="../reference/datamodel.html#object.__init__" title="object.__init__"><tt class="xref py py-meth docutils literal"><span class="pre">__init__()</span></tt></a>, it is possible to create an instance without calling
<a class="reference internal" href="../reference/datamodel.html#object.__init__" title="object.__init__"><tt class="xref py py-meth docutils literal"><span class="pre">__init__()</span></tt></a>, and it is possible to reinitialize an instance by calling its
<a class="reference internal" href="../reference/datamodel.html#object.__init__" title="object.__init__"><tt class="xref py py-meth docutils literal"><span class="pre">__init__()</span></tt></a> method again.</p>
<p>The function signature is</p>
<div class="highlight-c"><div class="highlight"><pre><span class="kt">int</span> <span class="n">tp_init</span><span class="p">(</span><span class="n">PyObject</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">kwds</span><span class="p">)</span>
</pre></div>
</div>
<p>The self argument is the instance to be initialized; the <em>args</em> and <em>kwds</em>
arguments represent positional and keyword arguments of the call to
<a class="reference internal" href="../reference/datamodel.html#object.__init__" title="object.__init__"><tt class="xref py py-meth docutils literal"><span class="pre">__init__()</span></tt></a>.</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_init</span></tt> function, if not <em>NULL</em>, is called when an instance is
created normally by calling its type, after the type’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt> function
has returned an instance of the type. If the <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt> function returns an
instance of some other type that is not a subtype of the original type, no
<tt class="xref py py-attr docutils literal"><span class="pre">tp_init</span></tt> function is called; if <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt> returns an instance of a
subtype of the original type, the subtype’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_init</span></tt> is called.</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_alloc">
allocfunc <tt class="descname">PyTypeObject.tp_alloc</tt><a class="headerlink" href="#PyTypeObject.tp_alloc" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to an instance allocation function.</p>
<p>The function signature is</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_alloc</span><span class="p">(</span><span class="n">PyTypeObject</span> <span class="o">*</span><span class="n">self</span><span class="p">,</span> <span class="n">Py_ssize_t</span> <span class="n">nitems</span><span class="p">)</span>
</pre></div>
</div>
<p>The purpose of this function is to separate memory allocation from memory
initialization. It should return a pointer to a block of memory of adequate
length for the instance, suitably aligned, and initialized to zeros, but with
<tt class="xref py py-attr docutils literal"><span class="pre">ob_refcnt</span></tt> set to <tt class="docutils literal"><span class="pre">1</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">ob_type</span></tt> set to the type argument. If
the type’s <tt class="xref py py-attr docutils literal"><span class="pre">tp_itemsize</span></tt> is non-zero, the object’s <tt class="xref py py-attr docutils literal"><span class="pre">ob_size</span></tt> field
should be initialized to <em>nitems</em> and the length of the allocated memory block
should be <tt class="docutils literal"><span class="pre">tp_basicsize</span> <span class="pre">+</span> <span class="pre">nitems*tp_itemsize</span></tt>, rounded up to a multiple of
<tt class="docutils literal"><span class="pre">sizeof(void*)</span></tt>; otherwise, <em>nitems</em> is not used and the length of the block
should be <tt class="xref py py-attr docutils literal"><span class="pre">tp_basicsize</span></tt>.</p>
<p>Do not use this function to do any other instance initialization, not even to
allocate additional memory; that should be done by <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt>.</p>
<p>This field is inherited by static subtypes, but not by dynamic subtypes
(subtypes created by a class statement); in the latter, this field is always set
to <a class="reference internal" href="type.html#PyType_GenericAlloc" title="PyType_GenericAlloc"><tt class="xref c c-func docutils literal"><span class="pre">PyType_GenericAlloc()</span></tt></a>, to force a standard heap allocation strategy.
That is also the recommended value for statically defined types.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_new">
newfunc <tt class="descname">PyTypeObject.tp_new</tt><a class="headerlink" href="#PyTypeObject.tp_new" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to an instance creation function.</p>
<p>If this function is <em>NULL</em> for a particular type, that type cannot be called to
create new instances; presumably there is some other way to create instances,
like a factory function.</p>
<p>The function signature is</p>
<div class="highlight-c"><div class="highlight"><pre><span class="n">PyObject</span> <span class="o">*</span><span class="n">tp_new</span><span class="p">(</span><span class="n">PyTypeObject</span> <span class="o">*</span><span class="n">subtype</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">kwds</span><span class="p">)</span>
</pre></div>
</div>
<p>The subtype argument is the type of the object being created; the <em>args</em> and
<em>kwds</em> arguments represent positional and keyword arguments of the call to the
type. Note that subtype doesn’t have to equal the type whose <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt>
function is called; it may be a subtype of that type (but not an unrelated
type).</p>
<p>The <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt> function should call <tt class="docutils literal"><span class="pre">subtype->tp_alloc(subtype,</span> <span class="pre">nitems)</span></tt>
to allocate space for the object, and then do only as much further
initialization as is absolutely necessary. Initialization that can safely be
ignored or repeated should be placed in the <tt class="xref py py-attr docutils literal"><span class="pre">tp_init</span></tt> handler. A good
rule of thumb is that for immutable types, all initialization should take place
in <tt class="xref py py-attr docutils literal"><span class="pre">tp_new</span></tt>, while for mutable types, most initialization should be
deferred to <tt class="xref py py-attr docutils literal"><span class="pre">tp_init</span></tt>.</p>
<p>This field is inherited by subtypes, except it is not inherited by static types
whose <tt class="xref py py-attr docutils literal"><span class="pre">tp_base</span></tt> is <em>NULL</em> or <tt class="docutils literal"><span class="pre">&PyBaseObject_Type</span></tt>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_free">
destructor <tt class="descname">PyTypeObject.tp_free</tt><a class="headerlink" href="#PyTypeObject.tp_free" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to an instance deallocation function. Its signature is
<tt class="xref c c-type docutils literal"><span class="pre">freefunc</span></tt>:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="kt">void</span> <span class="n">tp_free</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="p">)</span>
</pre></div>
</div>
<p>An initializer that is compatible with this signature is <tt class="xref c c-func docutils literal"><span class="pre">PyObject_Free()</span></tt>.</p>
<p>This field is inherited by static subtypes, but not by dynamic subtypes
(subtypes created by a class statement); in the latter, this field is set to a
deallocator suitable to match <a class="reference internal" href="type.html#PyType_GenericAlloc" title="PyType_GenericAlloc"><tt class="xref c c-func docutils literal"><span class="pre">PyType_GenericAlloc()</span></tt></a> and the value of the
<a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_is_gc">
<a class="reference internal" href="gcsupport.html#inquiry" title="inquiry">inquiry</a> <tt class="descname">PyTypeObject.tp_is_gc</tt><a class="headerlink" href="#PyTypeObject.tp_is_gc" title="Permalink to this definition">¶</a></dt>
<dd><p>An optional pointer to a function called by the garbage collector.</p>
<p>The garbage collector needs to know whether a particular object is collectible
or not. Normally, it is sufficient to look at the object’s type’s
<tt class="xref py py-attr docutils literal"><span class="pre">tp_flags</span></tt> field, and check the <a class="reference internal" href="#Py_TPFLAGS_HAVE_GC" title="Py_TPFLAGS_HAVE_GC"><tt class="xref py py-const docutils literal"><span class="pre">Py_TPFLAGS_HAVE_GC</span></tt></a> flag bit. But
some types have a mixture of statically and dynamically allocated instances, and
the statically allocated instances are not collectible. Such types should
define this function; it should return <tt class="docutils literal"><span class="pre">1</span></tt> for a collectible instance, and
<tt class="docutils literal"><span class="pre">0</span></tt> for a non-collectible instance. The signature is</p>
<div class="highlight-c"><div class="highlight"><pre><span class="kt">int</span> <span class="n">tp_is_gc</span><span class="p">(</span><span class="n">PyObject</span> <span class="o">*</span><span class="n">self</span><span class="p">)</span>
</pre></div>
</div>
<p>(The only example of this are types themselves. The metatype,
<a class="reference internal" href="type.html#PyType_Type" title="PyType_Type"><tt class="xref c c-data docutils literal"><span class="pre">PyType_Type</span></tt></a>, defines this function to distinguish between statically
and dynamically allocated types.)</p>
<p>This field is inherited by subtypes.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_bases">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyTypeObject.tp_bases</tt><a class="headerlink" href="#PyTypeObject.tp_bases" title="Permalink to this definition">¶</a></dt>
<dd><p>Tuple of base types.</p>
<p>This is set for types created by a class statement. It should be <em>NULL</em> for
statically defined types.</p>
<p>This field is not inherited.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_mro">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyTypeObject.tp_mro</tt><a class="headerlink" href="#PyTypeObject.tp_mro" title="Permalink to this definition">¶</a></dt>
<dd><p>Tuple containing the expanded set of base types, starting with the type itself
and ending with <a class="reference internal" href="../library/functions.html#object" title="object"><tt class="xref py py-class docutils literal"><span class="pre">object</span></tt></a>, in Method Resolution Order.</p>
<p>This field is not inherited; it is calculated fresh by <a class="reference internal" href="type.html#PyType_Ready" title="PyType_Ready"><tt class="xref c c-func docutils literal"><span class="pre">PyType_Ready()</span></tt></a>.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_cache">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyTypeObject.tp_cache</tt><a class="headerlink" href="#PyTypeObject.tp_cache" title="Permalink to this definition">¶</a></dt>
<dd><p>Unused. Not inherited. Internal use only.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_subclasses">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyTypeObject.tp_subclasses</tt><a class="headerlink" href="#PyTypeObject.tp_subclasses" title="Permalink to this definition">¶</a></dt>
<dd><p>List of weak references to subclasses. Not inherited. Internal use only.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_weaklist">
<a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyTypeObject.tp_weaklist</tt><a class="headerlink" href="#PyTypeObject.tp_weaklist" title="Permalink to this definition">¶</a></dt>
<dd><p>Weak reference list head, for weak references to this type object. Not
inherited. Internal use only.</p>
</dd></dl>
<p>The remaining fields are only defined if the feature test macro
<tt class="xref py py-const docutils literal"><span class="pre">COUNT_ALLOCS</span></tt> is defined, and are for internal use only. They are
documented here for completeness. None of these fields are inherited by
subtypes.</p>
<dl class="member">
<dt id="PyTypeObject.tp_allocs">
Py_ssize_t <tt class="descname">PyTypeObject.tp_allocs</tt><a class="headerlink" href="#PyTypeObject.tp_allocs" title="Permalink to this definition">¶</a></dt>
<dd><p>Number of allocations.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_frees">
Py_ssize_t <tt class="descname">PyTypeObject.tp_frees</tt><a class="headerlink" href="#PyTypeObject.tp_frees" title="Permalink to this definition">¶</a></dt>
<dd><p>Number of frees.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_maxalloc">
Py_ssize_t <tt class="descname">PyTypeObject.tp_maxalloc</tt><a class="headerlink" href="#PyTypeObject.tp_maxalloc" title="Permalink to this definition">¶</a></dt>
<dd><p>Maximum simultaneously allocated objects.</p>
</dd></dl>
<dl class="member">
<dt id="PyTypeObject.tp_next">
<a class="reference internal" href="type.html#PyTypeObject" title="PyTypeObject">PyTypeObject</a>* <tt class="descname">PyTypeObject.tp_next</tt><a class="headerlink" href="#PyTypeObject.tp_next" title="Permalink to this definition">¶</a></dt>
<dd><p>Pointer to the next type object with a non-zero <tt class="xref py py-attr docutils literal"><span class="pre">tp_allocs</span></tt> field.</p>
</dd></dl>
<p>Also, note that, in a garbage collected Python, tp_dealloc may be called from
any Python thread, not just the thread which created the object (if the object
becomes part of a refcount cycle, that cycle might be collected by a garbage
collection on any thread). This is not a problem for Python API calls, since
the thread on which tp_dealloc is called will own the Global Interpreter Lock
(GIL). However, if the object being destroyed in turn destroys objects from some
other C or C++ library, care should be taken to ensure that destroying those
objects on the thread which called tp_dealloc will not violate any assumptions
of the library.</p>
</div>
<div class="section" id="number-object-structures">
<span id="number-structs"></span><h1>Number Object Structures<a class="headerlink" href="#number-object-structures" title="Permalink to this headline">¶</a></h1>
<dl class="type">
<dt id="PyNumberMethods">
<tt class="descname">PyNumberMethods</tt><a class="headerlink" href="#PyNumberMethods" title="Permalink to this definition">¶</a></dt>
<dd><p>This structure holds pointers to the functions which an object uses to
implement the number protocol. Each function is used by the function of
similar name documented in the <a class="reference internal" href="number.html#number"><em>Number Protocol</em></a> section.</p>
<p>Here is the structure definition:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="k">typedef</span> <span class="k">struct</span> <span class="p">{</span>
<span class="n">binaryfunc</span> <span class="n">nb_add</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_subtract</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_multiply</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_remainder</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_divmod</span><span class="p">;</span>
<span class="n">ternaryfunc</span> <span class="n">nb_power</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_negative</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_positive</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_absolute</span><span class="p">;</span>
<span class="n">inquiry</span> <span class="n">nb_bool</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_invert</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_lshift</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_rshift</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_and</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_xor</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_or</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_int</span><span class="p">;</span>
<span class="kt">void</span> <span class="o">*</span><span class="n">nb_reserved</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_float</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_add</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_subtract</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_multiply</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_remainder</span><span class="p">;</span>
<span class="n">ternaryfunc</span> <span class="n">nb_inplace_power</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_lshift</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_rshift</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_and</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_xor</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_or</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_floor_divide</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_true_divide</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_floor_divide</span><span class="p">;</span>
<span class="n">binaryfunc</span> <span class="n">nb_inplace_true_divide</span><span class="p">;</span>
<span class="n">unaryfunc</span> <span class="n">nb_index</span><span class="p">;</span>
<span class="p">}</span> <span class="n">PyNumberMethods</span><span class="p">;</span>
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Binary and ternary functions must check the type of all their operands,
and implement the necessary conversions (at least one of the operands is
an instance of the defined type). If the operation is not defined for the
given operands, binary and ternary functions must return
<tt class="docutils literal"><span class="pre">Py_NotImplemented</span></tt>, if another error occurred they must return <tt class="docutils literal"><span class="pre">NULL</span></tt>
and set an exception.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <tt class="xref c c-data docutils literal"><span class="pre">nb_reserved</span></tt> field should always be <tt class="docutils literal"><span class="pre">NULL</span></tt>. It
was previously called <tt class="xref c c-data docutils literal"><span class="pre">nb_long</span></tt>, and was renamed in
Python 3.0.1.</p>
</div>
</dd></dl>
</div>
<div class="section" id="mapping-object-structures">
<span id="mapping-structs"></span><h1>Mapping Object Structures<a class="headerlink" href="#mapping-object-structures" title="Permalink to this headline">¶</a></h1>
<dl class="type">
<dt id="PyMappingMethods">
<tt class="descname">PyMappingMethods</tt><a class="headerlink" href="#PyMappingMethods" title="Permalink to this definition">¶</a></dt>
<dd><p>This structure holds pointers to the functions which an object uses to
implement the mapping protocol. It has three members:</p>
</dd></dl>
<dl class="member">
<dt id="PyMappingMethods.mp_length">
lenfunc <tt class="descname">PyMappingMethods.mp_length</tt><a class="headerlink" href="#PyMappingMethods.mp_length" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="mapping.html#PyMapping_Length" title="PyMapping_Length"><tt class="xref c c-func docutils literal"><span class="pre">PyMapping_Length()</span></tt></a> and
<a class="reference internal" href="object.html#PyObject_Size" title="PyObject_Size"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Size()</span></tt></a>, and has the same signature. This slot may be set to
<em>NULL</em> if the object has no defined length.</p>
</dd></dl>
<dl class="member">
<dt id="PyMappingMethods.mp_subscript">
binaryfunc <tt class="descname">PyMappingMethods.mp_subscript</tt><a class="headerlink" href="#PyMappingMethods.mp_subscript" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="object.html#PyObject_GetItem" title="PyObject_GetItem"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GetItem()</span></tt></a> and has the same
signature. This slot must be filled for the <a class="reference internal" href="mapping.html#PyMapping_Check" title="PyMapping_Check"><tt class="xref c c-func docutils literal"><span class="pre">PyMapping_Check()</span></tt></a>
function to return <tt class="docutils literal"><span class="pre">1</span></tt>, it can be <em>NULL</em> otherwise.</p>
</dd></dl>
<dl class="member">
<dt id="PyMappingMethods.mp_ass_subscript">
objobjargproc <tt class="descname">PyMappingMethods.mp_ass_subscript</tt><a class="headerlink" href="#PyMappingMethods.mp_ass_subscript" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="object.html#PyObject_SetItem" title="PyObject_SetItem"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_SetItem()</span></tt></a> and has the same
signature. If this slot is <em>NULL</em>, the object does not support item
assignment.</p>
</dd></dl>
</div>
<div class="section" id="sequence-object-structures">
<span id="sequence-structs"></span><h1>Sequence Object Structures<a class="headerlink" href="#sequence-object-structures" title="Permalink to this headline">¶</a></h1>
<dl class="type">
<dt id="PySequenceMethods">
<tt class="descname">PySequenceMethods</tt><a class="headerlink" href="#PySequenceMethods" title="Permalink to this definition">¶</a></dt>
<dd><p>This structure holds pointers to the functions which an object uses to
implement the sequence protocol.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_length">
lenfunc <tt class="descname">PySequenceMethods.sq_length</tt><a class="headerlink" href="#PySequenceMethods.sq_length" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_Size" title="PySequence_Size"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_Size()</span></tt></a> and <a class="reference internal" href="object.html#PyObject_Size" title="PyObject_Size"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_Size()</span></tt></a>,
and has the same signature.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_concat">
binaryfunc <tt class="descname">PySequenceMethods.sq_concat</tt><a class="headerlink" href="#PySequenceMethods.sq_concat" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_Concat" title="PySequence_Concat"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_Concat()</span></tt></a> and has the same
signature. It is also used by the <tt class="docutils literal"><span class="pre">+</span></tt> operator, after trying the numeric
addition via the <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_number.nb_add</span></tt> slot.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_repeat">
ssizeargfunc <tt class="descname">PySequenceMethods.sq_repeat</tt><a class="headerlink" href="#PySequenceMethods.sq_repeat" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_Repeat" title="PySequence_Repeat"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_Repeat()</span></tt></a> and has the same
signature. It is also used by the <tt class="docutils literal"><span class="pre">*</span></tt> operator, after trying numeric
multiplication via the <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_number.nb_mul</span></tt> slot.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_item">
ssizeargfunc <tt class="descname">PySequenceMethods.sq_item</tt><a class="headerlink" href="#PySequenceMethods.sq_item" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_GetItem" title="PySequence_GetItem"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_GetItem()</span></tt></a> and has the same
signature. This slot must be filled for the <a class="reference internal" href="sequence.html#PySequence_Check" title="PySequence_Check"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_Check()</span></tt></a>
function to return <tt class="docutils literal"><span class="pre">1</span></tt>, it can be <em>NULL</em> otherwise.</p>
<p>Negative indexes are handled as follows: if the <tt class="xref py py-attr docutils literal"><span class="pre">sq_length</span></tt> slot is
filled, it is called and the sequence length is used to compute a positive
index which is passed to <tt class="xref py py-attr docutils literal"><span class="pre">sq_item</span></tt>. If <tt class="xref py py-attr docutils literal"><span class="pre">sq_length</span></tt> is <em>NULL</em>,
the index is passed as is to the function.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_ass_item">
ssizeobjargproc <tt class="descname">PySequenceMethods.sq_ass_item</tt><a class="headerlink" href="#PySequenceMethods.sq_ass_item" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_SetItem" title="PySequence_SetItem"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_SetItem()</span></tt></a> and has the same
signature. This slot may be left to <em>NULL</em> if the object does not support
item assignment.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_contains">
objobjproc <tt class="descname">PySequenceMethods.sq_contains</tt><a class="headerlink" href="#PySequenceMethods.sq_contains" title="Permalink to this definition">¶</a></dt>
<dd><p>This function may be used by <a class="reference internal" href="sequence.html#PySequence_Contains" title="PySequence_Contains"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_Contains()</span></tt></a> and has the same
signature. This slot may be left to <em>NULL</em>, in this case
<a class="reference internal" href="sequence.html#PySequence_Contains" title="PySequence_Contains"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_Contains()</span></tt></a> simply traverses the sequence until it finds a
match.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_inplace_concat">
binaryfunc <tt class="descname">PySequenceMethods.sq_inplace_concat</tt><a class="headerlink" href="#PySequenceMethods.sq_inplace_concat" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_InPlaceConcat" title="PySequence_InPlaceConcat"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_InPlaceConcat()</span></tt></a> and has the same
signature. It should modify its first operand, and return it.</p>
</dd></dl>
<dl class="member">
<dt id="PySequenceMethods.sq_inplace_repeat">
ssizeargfunc <tt class="descname">PySequenceMethods.sq_inplace_repeat</tt><a class="headerlink" href="#PySequenceMethods.sq_inplace_repeat" title="Permalink to this definition">¶</a></dt>
<dd><p>This function is used by <a class="reference internal" href="sequence.html#PySequence_InPlaceRepeat" title="PySequence_InPlaceRepeat"><tt class="xref c c-func docutils literal"><span class="pre">PySequence_InPlaceRepeat()</span></tt></a> and has the same
signature. It should modify its first operand, and return it.</p>
</dd></dl>
</div>
<div class="section" id="buffer-object-structures">
<span id="buffer-structs"></span><h1>Buffer Object Structures<a class="headerlink" href="#buffer-object-structures" title="Permalink to this headline">¶</a></h1>
<p>The <a class="reference internal" href="buffer.html#bufferobjects"><em>buffer interface</em></a> exports a model where an object can expose its internal
data.</p>
<p>If an object does not export the buffer interface, then its <tt class="xref py py-attr docutils literal"><span class="pre">tp_as_buffer</span></tt>
member in the <a class="reference internal" href="type.html#PyTypeObject" title="PyTypeObject"><tt class="xref c c-type docutils literal"><span class="pre">PyTypeObject</span></tt></a> structure should be <em>NULL</em>. Otherwise, the
<tt class="xref py py-attr docutils literal"><span class="pre">tp_as_buffer</span></tt> will point to a <a class="reference internal" href="#PyBufferProcs" title="PyBufferProcs"><tt class="xref c c-type docutils literal"><span class="pre">PyBufferProcs</span></tt></a> structure.</p>
<dl class="type">
<dt id="PyBufferProcs">
<tt class="descname">PyBufferProcs</tt><a class="headerlink" href="#PyBufferProcs" title="Permalink to this definition">¶</a></dt>
<dd><p>Structure used to hold the function pointers which define an implementation of
the buffer protocol.</p>
<dl class="member">
<dt id="PyBufferProcs.bf_getbuffer">
getbufferproc <tt class="descname">bf_getbuffer</tt><a class="headerlink" href="#PyBufferProcs.bf_getbuffer" title="Permalink to this definition">¶</a></dt>
<dd><p>This should fill a <a class="reference internal" href="buffer.html#Py_buffer" title="Py_buffer"><tt class="xref c c-type docutils literal"><span class="pre">Py_buffer</span></tt></a> with the necessary data for
exporting the type. The signature of <tt class="xref py py-data docutils literal"><span class="pre">getbufferproc</span></tt> is <tt class="docutils literal"><span class="pre">int</span>
<span class="pre">(PyObject</span> <span class="pre">*obj,</span> <span class="pre">Py_buffer</span> <span class="pre">*view,</span> <span class="pre">int</span> <span class="pre">flags)</span></tt>. <em>obj</em> is the object to
export, <em>view</em> is the <a class="reference internal" href="buffer.html#Py_buffer" title="Py_buffer"><tt class="xref c c-type docutils literal"><span class="pre">Py_buffer</span></tt></a> struct to fill, and <em>flags</em> gives
the conditions the caller wants the memory under. (See
<a class="reference internal" href="buffer.html#PyObject_GetBuffer" title="PyObject_GetBuffer"><tt class="xref c c-func docutils literal"><span class="pre">PyObject_GetBuffer()</span></tt></a> for all flags.) <tt class="xref c c-member docutils literal"><span class="pre">bf_getbuffer</span></tt> is
responsible for filling <em>view</em> with the appropriate information.
(<tt class="xref c c-func docutils literal"><span class="pre">PyBuffer_FillView()</span></tt> can be used in simple cases.) See
<a class="reference internal" href="buffer.html#Py_buffer" title="Py_buffer"><tt class="xref c c-type docutils literal"><span class="pre">Py_buffer</span></tt></a>s docs for what needs to be filled in.</p>
</dd></dl>
<dl class="member">
<dt id="PyBufferProcs.bf_releasebuffer">
releasebufferproc <tt class="descname">bf_releasebuffer</tt><a class="headerlink" href="#PyBufferProcs.bf_releasebuffer" title="Permalink to this definition">¶</a></dt>
<dd><p>This should release the resources of the buffer. The signature of
<tt class="xref c c-data docutils literal"><span class="pre">releasebufferproc</span></tt> is <tt class="docutils literal"><span class="pre">void</span> <span class="pre">(PyObject</span> <span class="pre">*obj,</span> <span class="pre">Py_buffer</span> <span class="pre">*view)</span></tt>.
If the <tt class="xref c c-data docutils literal"><span class="pre">bf_releasebuffer</span></tt> function is not provided (i.e. it is
<em>NULL</em>), then it does not ever need to be called.</p>
<p>The exporter of the buffer interface must make sure that any memory
pointed to in the <a class="reference internal" href="buffer.html#Py_buffer" title="Py_buffer"><tt class="xref c c-type docutils literal"><span class="pre">Py_buffer</span></tt></a> structure remains valid until
releasebuffer is called. Exporters will need to define a
<tt class="xref c c-data docutils literal"><span class="pre">bf_releasebuffer</span></tt> function if they can re-allocate their memory,
strides, shape, suboffsets, or format variables which they might share
through the struct bufferinfo.</p>
<p>See <a class="reference internal" href="buffer.html#PyBuffer_Release" title="PyBuffer_Release"><tt class="xref c c-func docutils literal"><span class="pre">PyBuffer_Release()</span></tt></a>.</p>
</dd></dl>
</dd></dl>
</div>
</div>
</div>
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<ul>
<li><a class="reference internal" href="#">Type Objects</a></li>
<li><a class="reference internal" href="#number-object-structures">Number Object Structures</a></li>
<li><a class="reference internal" href="#mapping-object-structures">Mapping Object Structures</a></li>
<li><a class="reference internal" href="#sequence-object-structures">Sequence Object Structures</a></li>
<li><a class="reference internal" href="#buffer-object-structures">Buffer Object Structures</a></li>
</ul>
<h4>Previous topic</h4>
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