Doc/c-api/typeobj.rst
.. highlight:: c
.. _type-structs:
Perhaps one of the most important structures of the Python object system is the
structure that defines a new type: the :c:type:PyTypeObject structure. Type
objects can be handled using any of the PyObject_* or
PyType_* 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.
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.
In addition to the following quick reference, the :ref:typedef-examples
section provides at-a-glance insight into the meaning and use of
:c:type:PyTypeObject.
.. _tp-slots-table:
"tp slots" ^^^^^^^^^^
.. table:: :widths: 18,18,18,1,1,1,1
+------------------------------------------------+-----------------------------------+-------------------+---------------+
| PyTypeObject Slot [#slots]_ | :ref:Type <slot-typedefs-table> | special | Info [#cols]_ |
| | | methods/attrs +---+---+---+---+
| | | | O | T | D | I |
+================================================+===================================+===================+===+===+===+===+
| <R> :c:member:~PyTypeObject.tp_name | const char * | name | X | X | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_basicsize | :c:type:Py_ssize_t | | X | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_itemsize | :c:type:Py_ssize_t | | | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_dealloc | :c:type:destructor | | X | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_vectorcall_offset | :c:type:Py_ssize_t | | | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| (:c:member:~PyTypeObject.tp_getattr) | :c:type:getattrfunc | getattribute, | | | | G |
| | | getattr | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| (:c:member:~PyTypeObject.tp_setattr) | :c:type:setattrfunc | setattr, | | | | G |
| | | delattr | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_as_async | :c:type:PyAsyncMethods * | :ref:sub-slots | | | | % |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_repr | :c:type:reprfunc | repr | X | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_as_number | :c:type:PyNumberMethods * | :ref:sub-slots | | | | % |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_as_sequence | :c:type:PySequenceMethods * | :ref:sub-slots | | | | % |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_as_mapping | :c:type:PyMappingMethods * | :ref:sub-slots | | | | % |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_hash | :c:type:hashfunc | hash | X | | | G |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_call | :c:type:ternaryfunc | call | | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_str | :c:type:reprfunc | str | X | | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_getattro | :c:type:getattrofunc | getattribute, | X | X | | G |
| | | getattr | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_setattro | :c:type:setattrofunc | setattr, | X | X | | G |
| | | delattr | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_as_buffer | :c:type:PyBufferProcs * | :ref:sub-slots | | | | % |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_flags | unsigned long | | X | X | | ? |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_doc | const char * | doc | X | X | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_traverse | :c:type:traverseproc | | | X | | G |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_clear | :c:type:inquiry | | | X | | G |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_richcompare | :c:type:richcmpfunc | lt, | X | | | G |
| | | le, | | | | |
| | | eq, | | | | |
| | | ne, | | | | |
| | | gt, | | | | |
| | | ge | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| (:c:member:~PyTypeObject.tp_weaklistoffset) | :c:type:Py_ssize_t | | | X | | ? |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_iter | :c:type:getiterfunc | iter | | | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_iternext | :c:type:iternextfunc | next | | | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_methods | :c:type:PyMethodDef [] | | X | X | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_members | :c:type:PyMemberDef [] | | | X | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_getset | :c:type:PyGetSetDef [] | | X | X | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_base | :c:type:PyTypeObject * | base | | | X | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_dict | :c:type:PyObject * | dict | | | ? | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_descr_get | :c:type:descrgetfunc | get | | | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_descr_set | :c:type:descrsetfunc | set, | | | | X |
| | | delete | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| (:c:member:~PyTypeObject.tp_dictoffset) | :c:type:Py_ssize_t | | | X | | ? |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_init | :c:type:initproc | init | X | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_alloc | :c:type:allocfunc | | X | | ? | ? |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_new | :c:type:newfunc | new | X | X | ? | ? |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_free | :c:type:freefunc | | X | X | ? | ? |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_is_gc | :c:type:inquiry | | | X | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| <:c:member:~PyTypeObject.tp_bases> | :c:type:PyObject * | bases | | | ~ | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| <:c:member:~PyTypeObject.tp_mro> | :c:type:PyObject * | mro | | | ~ | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| [:c:member:~PyTypeObject.tp_cache] | :c:type:PyObject * | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| [:c:member:~PyTypeObject.tp_subclasses] | void * | subclasses | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| [:c:member:~PyTypeObject.tp_weaklist] | :c:type:PyObject * | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| (:c:member:~PyTypeObject.tp_del) | :c:type:destructor | | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| [:c:member:~PyTypeObject.tp_version_tag] | unsigned int | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_finalize | :c:type:destructor | del | | | | X |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| :c:member:~PyTypeObject.tp_vectorcall | :c:type:vectorcallfunc | | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
| [:c:member:~PyTypeObject.tp_watched] | unsigned char | | | | | |
+------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
.. [#slots]
(): A slot name in parentheses indicates it is (effectively) deprecated.
<>: Names in angle brackets should be initially set to NULL and
treated as read-only.
[]: Names in square brackets are for internal use only.
<R> (as a prefix) means the field is required (must be non-NULL).
.. [#cols] Columns:
"O": set on :c:data:PyBaseObject_Type
"T": set on :c:data:PyType_Type
"D": default (if slot is set to NULL)
.. code-block:: none
X - PyType_Ready sets this value if it is NULL
~ - PyType_Ready always sets this value (it should be NULL)
? - PyType_Ready may set this value depending on other slots
Also see the inheritance column ("I").
"I": inheritance
.. code-block:: none
X - type slot is inherited via *PyType_Ready* if defined with a *NULL* value
% - the slots of the sub-struct are inherited individually
G - inherited, but only in combination with other slots; see the slot's description
? - it's complicated; see the slot's description
Note that some slots are effectively inherited through the normal attribute lookup chain.
.. _sub-slots:
sub-slots ^^^^^^^^^
.. table:: :widths: 26,17,12
+---------------------------------------------------------+-----------------------------------+---------------+
| Slot | :ref:Type <slot-typedefs-table> | special |
| | | methods |
+=========================================================+===================================+===============+
| :c:member:~PyAsyncMethods.am_await | :c:type:unaryfunc | await |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyAsyncMethods.am_aiter | :c:type:unaryfunc | aiter |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyAsyncMethods.am_anext | :c:type:unaryfunc | anext |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyAsyncMethods.am_send | :c:type:sendfunc | |
+---------------------------------------------------------+-----------------------------------+---------------+
| |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_add | :c:type:binaryfunc | add |
| | | radd |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_add | :c:type:binaryfunc | iadd |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_subtract | :c:type:binaryfunc | sub |
| | | rsub |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_subtract | :c:type:binaryfunc | isub |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_multiply | :c:type:binaryfunc | mul |
| | | rmul |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_multiply | :c:type:binaryfunc | imul |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_remainder | :c:type:binaryfunc | mod |
| | | rmod |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_remainder | :c:type:binaryfunc | imod |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_divmod | :c:type:binaryfunc | divmod |
| | | rdivmod |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_power | :c:type:ternaryfunc | pow |
| | | rpow |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_power | :c:type:ternaryfunc | ipow |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_negative | :c:type:unaryfunc | neg |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_positive | :c:type:unaryfunc | pos |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_absolute | :c:type:unaryfunc | abs |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_bool | :c:type:inquiry | bool |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_invert | :c:type:unaryfunc | invert |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_lshift | :c:type:binaryfunc | lshift |
| | | rlshift |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_lshift | :c:type:binaryfunc | ilshift |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_rshift | :c:type:binaryfunc | rshift |
| | | rrshift |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_rshift | :c:type:binaryfunc | irshift |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_and | :c:type:binaryfunc | and |
| | | rand |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_and | :c:type:binaryfunc | iand |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_xor | :c:type:binaryfunc | xor |
| | | rxor |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_xor | :c:type:binaryfunc | ixor |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_or | :c:type:binaryfunc | or |
| | | ror |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_or | :c:type:binaryfunc | ior |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_int | :c:type:unaryfunc | int |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_reserved | void * | |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_float | :c:type:unaryfunc | float |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_floor_divide | :c:type:binaryfunc | floordiv |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_floor_divide | :c:type:binaryfunc | ifloordiv |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_true_divide | :c:type:binaryfunc | truediv |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_true_divide | :c:type:binaryfunc | itruediv |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_index | :c:type:unaryfunc | index |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_matrix_multiply | :c:type:binaryfunc | matmul |
| | | rmatmul |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyNumberMethods.nb_inplace_matrix_multiply | :c:type:binaryfunc | imatmul |
+---------------------------------------------------------+-----------------------------------+---------------+
| |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyMappingMethods.mp_length | :c:type:lenfunc | len |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyMappingMethods.mp_subscript | :c:type:binaryfunc | getitem |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyMappingMethods.mp_ass_subscript | :c:type:objobjargproc | setitem, |
| | | delitem |
+---------------------------------------------------------+-----------------------------------+---------------+
| |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_length | :c:type:lenfunc | len |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_concat | :c:type:binaryfunc | add |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_repeat | :c:type:ssizeargfunc | mul |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_item | :c:type:ssizeargfunc | getitem |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_ass_item | :c:type:ssizeobjargproc | setitem |
| | | delitem |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_contains | :c:type:objobjproc | contains |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_inplace_concat | :c:type:binaryfunc | iadd |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PySequenceMethods.sq_inplace_repeat | :c:type:ssizeargfunc | imul |
+---------------------------------------------------------+-----------------------------------+---------------+
| |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyBufferProcs.bf_getbuffer | :c:func:getbufferproc | buffer |
+---------------------------------------------------------+-----------------------------------+---------------+
| :c:member:~PyBufferProcs.bf_releasebuffer | :c:func:releasebufferproc | release\ |
| | | buffer_ |
+---------------------------------------------------------+-----------------------------------+---------------+
.. _slot-typedefs-table:
slot typedefs ^^^^^^^^^^^^^
+-----------------------------+-----------------------------+----------------------+
| typedef | Parameter Types | Return Type |
+=============================+=============================+======================+
| :c:type:allocfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyTypeObject * | |
| | :c:type:Py_ssize_t | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:destructor | :c:type:PyObject * | void |
+-----------------------------+-----------------------------+----------------------+
| :c:type:freefunc | void * | void |
+-----------------------------+-----------------------------+----------------------+
| :c:type:traverseproc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:visitproc | |
| | void * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:newfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyTypeObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:initproc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:reprfunc | :c:type:PyObject * | :c:type:PyObject * |
+-----------------------------+-----------------------------+----------------------+
| :c:type:getattrfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | const char * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:setattrfunc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | const char * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:getattrofunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:setattrofunc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:descrgetfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:descrsetfunc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:hashfunc | :c:type:PyObject * | Py_hash_t |
+-----------------------------+-----------------------------+----------------------+
| :c:type:richcmpfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | int | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:getiterfunc | :c:type:PyObject * | :c:type:PyObject * |
+-----------------------------+-----------------------------+----------------------+
| :c:type:iternextfunc | :c:type:PyObject * | :c:type:PyObject * |
+-----------------------------+-----------------------------+----------------------+
| :c:type:lenfunc | :c:type:PyObject * | :c:type:Py_ssize_t |
+-----------------------------+-----------------------------+----------------------+
| :c:type:getbufferproc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:Py_buffer * | |
| | int | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:releasebufferproc | .. line-block:: | void |
| | | |
| | :c:type:PyObject * | |
| | :c:type:Py_buffer * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:inquiry | :c:type:PyObject * | int |
+-----------------------------+-----------------------------+----------------------+
| :c:type:unaryfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:binaryfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:ternaryfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:ssizeargfunc | .. line-block:: | :c:type:PyObject * |
| | | |
| | :c:type:PyObject * | |
| | :c:type:Py_ssize_t | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:ssizeobjargproc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:Py_ssize_t | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:objobjproc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
| :c:type:objobjargproc | .. line-block:: | int |
| | | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
| | :c:type:PyObject * | |
+-----------------------------+-----------------------------+----------------------+
See :ref:slot-typedefs below for more detail.
The structure definition for :c:type:PyTypeObject can be found in
:file:Include/cpython/object.h. For convenience of reference, this repeats the
definition found there:
.. XXX Drop this?
.. literalinclude:: ../includes/typestruct.h
The type object structure extends the :c:type:PyVarObject structure. The
:c:member:~PyVarObject.ob_size field is used for dynamic types (created by :c:func:!type_new,
usually called from a class statement). Note that :c:data:PyType_Type (the
metatype) initializes :c:member:~PyTypeObject.tp_itemsize, which means that its instances (i.e.
type objects) must have the :c:member:~PyVarObject.ob_size field.
:c:member:PyObject.ob_refcnt
The type object's reference count is initialized to 1 by the
PyObject_HEAD_INIT macro. Note that for :ref:statically allocated type objects <static-types>, the type's instances (objects whose :c:member:~PyObject.ob_type
points back to the type) do not count as references. But for
:ref:dynamically allocated type objects <heap-types>, the instances do
count as references.
Inheritance:
This field is not inherited by subtypes.
:c:member:PyObject.ob_type
This is the type's type, in other words its metatype. It is initialized by the
argument to the PyObject_HEAD_INIT macro, and its value should normally be
&PyType_Type. 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 NULL to the
PyObject_HEAD_INIT 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::
Foo_Type.ob_type = &PyType_Type;
This should be done before any instances of the type are created.
:c:func:PyType_Ready checks if :c:member:~PyObject.ob_type is NULL, and if so,
initializes it to the :c:member:~PyObject.ob_type field of the base class.
:c:func:PyType_Ready will not change this field if it is non-zero.
Inheritance:
This field is inherited by subtypes.
:c:member:PyVarObject.ob_size
For :ref:statically allocated type objects <static-types>, this should be
initialized to zero. For :ref:dynamically allocated type objects <heap-types>, this field has a special internal meaning.
This field should be accessed using the :c:func:Py_SIZE() macro.
Inheritance:
This field is not inherited by subtypes.
Each slot has a section describing inheritance. If :c:func:PyType_Ready
may set a value when the field is set to NULL then there will also be
a "Default" section. (Note that many fields set on :c:data:PyBaseObject_Type
and :c:data:PyType_Type effectively act as defaults.)
.. c:member:: const char* PyTypeObject.tp_name
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
:class:!T defined in module :mod:!M in subpackage :mod:!Q in package :mod:!P
should have the :c:member:~PyTypeObject.tp_name initializer "P.Q.M.T".
For :ref:dynamically allocated type objects <heap-types>,
this should just be the type name, and
the module name explicitly stored in the type dict as the value for key
'__module__'.
For :ref:statically allocated type objects <static-types>,
the tp_name field should contain a dot.
Everything before the last dot is made accessible as the :attr:~type.__module__
attribute, and everything after the last dot is made accessible as the
:attr:~type.__name__ attribute.
If no dot is present, the entire :c:member:~PyTypeObject.tp_name field is made accessible as the
:attr:~type.__name__ attribute, and the :attr:~type.__module__ attribute is undefined
(unless explicitly set in the dictionary, as explained above). This means your
type will be impossible to pickle. Additionally, it will not be listed in
module documentations created with pydoc.
This field must not be NULL. It is the only required field
in :c:func:PyTypeObject (other than potentially
:c:member:~PyTypeObject.tp_itemsize).
Inheritance:
This field is not inherited by subtypes.
.. c:member:: Py_ssize_t PyTypeObject.tp_basicsize Py_ssize_t PyTypeObject.tp_itemsize
These fields allow calculating the size in bytes of instances of the type.
There are two kinds of types: types with fixed-length instances have a zero
:c:member:!tp_itemsize field, types with variable-length instances have a non-zero
:c:member:!tp_itemsize field. For a type with fixed-length instances, all
instances have the same size, given in :c:member:!tp_basicsize.
(Exceptions to this rule can be made using
:c:func:PyUnstable_Object_GC_NewWithExtraData.)
For a type with variable-length instances, the instances must have an
:c:member:~PyVarObject.ob_size field, and the instance size is
:c:member:!tp_basicsize plus N times :c:member:!tp_itemsize,
where N is the "length" of the object.
Functions like :c:func:PyObject_NewVar will take the value of N as an
argument, and store in the instance's :c:member:~PyVarObject.ob_size field.
Note that the :c:member:~PyVarObject.ob_size field may later be used for
other purposes. For example, :py:type:int instances use the bits of
:c:member:~PyVarObject.ob_size in an implementation-defined
way; the underlying storage and its size should be accessed using
:c:func:PyLong_Export.
.. note::
The :c:member:`~PyVarObject.ob_size` field should be accessed using
the :c:func:`Py_SIZE()` and :c:func:`Py_SET_SIZE()` macros.
Also, the presence of an :c:member:~PyVarObject.ob_size field in the
instance layout doesn't mean that the instance structure is variable-length.
For example, the :py:type:list type has fixed-length instances, yet those
instances have a :c:member:~PyVarObject.ob_size field.
(As with :py:type:int, avoid reading lists' :c:member:!ob_size directly.
Call :c:func:PyList_Size instead.)
The :c:member:!tp_basicsize includes size needed for data of the type's
:c:member:~PyTypeObject.tp_base, plus any extra data needed
by each instance.
The correct way to set :c:member:!tp_basicsize is to use the
sizeof operator on the struct used to declare the instance layout.
This struct must include the struct used to declare the base type.
In other words, :c:member:!tp_basicsize must be greater than or equal
to the base's :c:member:!tp_basicsize.
Since every type is a subtype of :py:type:object, this struct must
include :c:type:PyObject or :c:type:PyVarObject (depending on
whether :c:member:~PyVarObject.ob_size should be included). These are
usually defined by the macro :c:macro:PyObject_HEAD or
:c:macro:PyObject_VAR_HEAD, respectively.
The basic size does not include the GC header size, as that header is not
part of :c:macro:PyObject_HEAD.
For cases where struct used to declare the base type is unknown,
see :c:member:PyType_Spec.basicsize and :c:func:PyType_FromMetaclass.
Notes about alignment:
!tp_basicsize must be a multiple of _Alignof(PyObject).
When using sizeof on a struct that includes
:c:macro:PyObject_HEAD, as recommended, the compiler ensures this.
When not using a C struct, or when using compiler
extensions like __attribute__((packed)), it is up to you.!tp_basicsize and :c:member:!tp_itemsize must each be a
multiple of that alignment.
For example, if a type's variable part stores a double, it is
your responsibility that both fields are a multiple of
_Alignof(double).Inheritance:
These fields are inherited separately by subtypes.
(That is, if the field is set to zero, :c:func:PyType_Ready will copy
the value from the base type, indicating that the instances do not
need additional storage.)
If the base type has a non-zero :c:member:~PyTypeObject.tp_itemsize, it is generally not safe to set
:c:member:~PyTypeObject.tp_itemsize to a different non-zero value in a subtype (though this
depends on the implementation of the base type).
.. c:member:: destructor PyTypeObject.tp_dealloc
.. corresponding-type-slot:: Py_tp_dealloc
A pointer to the instance destructor function. The function signature is::
void tp_dealloc(PyObject *self);
The destructor function should remove all references which the instance owns
(e.g., call :c:func:Py_CLEAR), free all memory buffers owned by the
instance, and call the type's :c:member:~PyTypeObject.tp_free function to
free the object itself.
If you may call functions that may set the error indicator, you must use
:c:func:PyErr_GetRaisedException and :c:func:PyErr_SetRaisedException
to ensure you don't clobber a preexisting error indicator (the deallocation
could have occurred while processing a different error):
.. code-block:: c
static void
foo_dealloc(foo_object *self)
{
PyObject *et, *ev, *etb;
PyObject *exc = PyErr_GetRaisedException();
...
PyErr_SetRaisedException(exc);
}
The dealloc handler itself must not raise an exception; if it hits an error
case it should call :c:func:PyErr_FormatUnraisable to log (and clear) an
unraisable exception.
No guarantees are made about when an object is destroyed, except:
~PyTypeObject.tp_finalize) subsequently resurrects the
object.~PyTypeObject.tp_finalize) or automatically cleared
(:c:member:~PyTypeObject.tp_clear).CPython currently destroys an object immediately from :c:func:Py_DECREF
when the new reference count is zero, but this may change in a future
version.
It is recommended to call :c:func:PyObject_CallFinalizerFromDealloc at the
beginning of :c:member:!tp_dealloc to guarantee that the object is always
finalized before destruction.
If the type supports garbage collection (the :c:macro:Py_TPFLAGS_HAVE_GC
flag is set), the destructor should call :c:func:PyObject_GC_UnTrack
before clearing any member fields.
It is permissible to call :c:member:~PyTypeObject.tp_clear from
:c:member:!tp_dealloc to reduce code duplication and to guarantee that the
object is always cleared before destruction. Beware that
:c:member:!tp_clear might have already been called.
If the type is heap allocated (:c:macro:Py_TPFLAGS_HEAPTYPE), the
deallocator should release the owned reference to its type object (via
:c:func:Py_DECREF) after calling the type deallocator. See the example
code below.::
static void
foo_dealloc(PyObject *op)
{
foo_object *self = (foo_object *) op;
PyObject_GC_UnTrack(self);
Py_CLEAR(self->ref);
Py_TYPE(self)->tp_free(self);
}
:c:member:!tp_dealloc must leave the exception status unchanged. If it
needs to call something that might raise an exception, the exception state
must be backed up first and restored later (after logging any exceptions
with :c:func:PyErr_WriteUnraisable).
Example::
static void
foo_dealloc(PyObject *self)
{
PyObject *exc = PyErr_GetRaisedException();
if (PyObject_CallFinalizerFromDealloc(self) < 0) {
// self was resurrected.
goto done;
}
PyTypeObject *tp = Py_TYPE(self);
if (tp->tp_flags & Py_TPFLAGS_HAVE_GC) {
PyObject_GC_UnTrack(self);
}
// Optional, but convenient to avoid code duplication.
if (tp->tp_clear && tp->tp_clear(self) < 0) {
PyErr_WriteUnraisable(self);
}
// Any additional destruction goes here.
tp->tp_free(self);
self = NULL; // In case PyErr_WriteUnraisable() is called below.
if (tp->tp_flags & Py_TPFLAGS_HEAPTYPE) {
Py_CLEAR(tp);
}
done:
// Optional, if something was called that might have raised an
// exception.
if (PyErr_Occurred()) {
PyErr_WriteUnraisable(self);
}
PyErr_SetRaisedException(exc);
}
:c:member:!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 :c:member:!tp_dealloc is called
with an :term:attached thread state. However, if the object being
destroyed in turn destroys objects from some other C library, care
should be taken to ensure that destroying those objects on the thread
which called :c:member:!tp_dealloc will not violate any assumptions of
the library.
Inheritance:
This field is inherited by subtypes.
.. seealso::
:ref:`life-cycle` for details about how this slot relates to other slots.
.. c:member:: Py_ssize_t PyTypeObject.tp_vectorcall_offset
An optional offset to a per-instance function that implements calling
the object using the :ref:vectorcall protocol <vectorcall>,
a more efficient alternative
of the simpler :c:member:~PyTypeObject.tp_call.
This field is only used if the flag :c:macro:Py_TPFLAGS_HAVE_VECTORCALL
is set. If so, this must be a positive integer containing the offset in the
instance of a :c:type:vectorcallfunc pointer.
The vectorcallfunc pointer may be NULL, in which case the instance behaves
as if :c:macro:Py_TPFLAGS_HAVE_VECTORCALL was not set: calling the instance
falls back to :c:member:~PyTypeObject.tp_call.
Any class that sets Py_TPFLAGS_HAVE_VECTORCALL must also set
:c:member:~PyTypeObject.tp_call and make sure its behaviour is consistent
with the vectorcallfunc function.
This can be done by setting tp_call to :c:func:PyVectorcall_Call.
.. versionchanged:: 3.8
Before version 3.8, this slot was named ``tp_print``.
In Python 2.x, it was used for printing to a file.
In Python 3.0 to 3.7, it was unused.
.. versionchanged:: 3.12
Before version 3.12, it was not recommended for
:ref:`mutable heap types <heap-types>` to implement the vectorcall
protocol.
When a user sets :attr:`~object.__call__` in Python code, only *tp_call* is
updated, likely making it inconsistent with the vectorcall function.
Since 3.12, setting ``__call__`` will disable vectorcall optimization
by clearing the :c:macro:`Py_TPFLAGS_HAVE_VECTORCALL` flag.
Inheritance:
This field is always inherited.
However, the :c:macro:Py_TPFLAGS_HAVE_VECTORCALL flag is not
always inherited. If it's not set, then the subclass won't use
:ref:vectorcall <vectorcall>, except when
:c:func:PyVectorcall_Call is explicitly called.
.. c:member:: getattrfunc PyTypeObject.tp_getattr
.. corresponding-type-slot:: Py_tp_getattr
An optional pointer to the get-attribute-string function.
This field is deprecated. When it is defined, it should point to a function
that acts the same as the :c:member:~PyTypeObject.tp_getattro function, but taking a C string
instead of a Python string object to give the attribute name.
Inheritance:
Group: :c:member:~PyTypeObject.tp_getattr, :c:member:~PyTypeObject.tp_getattro
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_getattro: a subtype
inherits both :c:member:~PyTypeObject.tp_getattr and :c:member:~PyTypeObject.tp_getattro from its base type when
the subtype's :c:member:~PyTypeObject.tp_getattr and :c:member:~PyTypeObject.tp_getattro are both NULL.
.. c:member:: setattrfunc PyTypeObject.tp_setattr
.. corresponding-type-slot:: Py_tp_setattr
An optional pointer to the function for setting and deleting attributes.
This field is deprecated. When it is defined, it should point to a function
that acts the same as the :c:member:~PyTypeObject.tp_setattro function, but taking a C string
instead of a Python string object to give the attribute name.
Inheritance:
Group: :c:member:~PyTypeObject.tp_setattr, :c:member:~PyTypeObject.tp_setattro
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_setattro: a subtype
inherits both :c:member:~PyTypeObject.tp_setattr and :c:member:~PyTypeObject.tp_setattro from its base type when
the subtype's :c:member:~PyTypeObject.tp_setattr and :c:member:~PyTypeObject.tp_setattro are both NULL.
.. c:member:: PyAsyncMethods* PyTypeObject.tp_as_async
Pointer to an additional structure that contains fields relevant only to
objects which implement :term:awaitable and :term:asynchronous iterator
protocols at the C-level. See :ref:async-structs for details.
.. versionadded:: 3.5
Formerly known as tp_compare and tp_reserved.
Inheritance:
The :c:member:~PyTypeObject.tp_as_async field is not inherited,
but the contained fields are inherited individually.
.. c:member:: reprfunc PyTypeObject.tp_repr
.. corresponding-type-slot:: Py_tp_repr
.. index:: pair: built-in function; repr
An optional pointer to a function that implements the built-in function
:func:repr.
The signature is the same as for :c:func:PyObject_Repr::
PyObject *tp_repr(PyObject *self);
The function must return a string or a Unicode object. Ideally,
this function should return a string that, when passed to
:func:eval, given a suitable environment, returns an object with the
same value. If this is not feasible, it should return a string starting with
'<' and ending with '>' from which both the type and the value of the
object can be deduced.
Inheritance:
This field is inherited by subtypes.
Default:
When this field is not set, a string of the form <%s object at %p> is
returned, where %s is replaced by the type name, and %p by the object's
memory address.
.. c:member:: PyNumberMethods* PyTypeObject.tp_as_number
Pointer to an additional structure that contains fields relevant only to
objects which implement the number protocol. These fields are documented in
:ref:number-structs.
Inheritance:
The :c:member:~PyTypeObject.tp_as_number field is not inherited, but the contained fields are
inherited individually.
.. c:member:: PySequenceMethods* PyTypeObject.tp_as_sequence
Pointer to an additional structure that contains fields relevant only to
objects which implement the sequence protocol. These fields are documented
in :ref:sequence-structs.
Inheritance:
The :c:member:~PyTypeObject.tp_as_sequence field is not inherited, but the contained fields
are inherited individually.
.. c:member:: PyMappingMethods* PyTypeObject.tp_as_mapping
Pointer to an additional structure that contains fields relevant only to
objects which implement the mapping protocol. These fields are documented in
:ref:mapping-structs.
Inheritance:
The :c:member:~PyTypeObject.tp_as_mapping field is not inherited, but the contained fields
are inherited individually.
.. c:member:: hashfunc PyTypeObject.tp_hash
.. corresponding-type-slot:: Py_tp_hash
.. index:: pair: built-in function; hash
An optional pointer to a function that implements the built-in function
:func:hash.
The signature is the same as for :c:func:PyObject_Hash::
Py_hash_t tp_hash(PyObject *);
The value -1 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 -1.
When this field is not set (and :c:member:~PyTypeObject.tp_richcompare is not set),
an attempt to take the hash of the object raises :exc:TypeError.
This is the same as setting it to :c:func:PyObject_HashNotImplemented.
This field can be set explicitly to :c:func:PyObject_HashNotImplemented to
block inheritance of the hash method from a parent type. This is interpreted
as the equivalent of __hash__ = None at the Python level, causing
isinstance(o, collections.Hashable) to correctly return False. Note
that the converse is also true - setting __hash__ = None on a class at
the Python level will result in the tp_hash slot being set to
:c:func:PyObject_HashNotImplemented.
Inheritance:
Group: :c:member:~PyTypeObject.tp_hash, :c:member:~PyTypeObject.tp_richcompare
This field is inherited by subtypes together with
:c:member:~PyTypeObject.tp_richcompare: a subtype inherits both of
:c:member:~PyTypeObject.tp_richcompare and :c:member:~PyTypeObject.tp_hash, when the subtype's
:c:member:~PyTypeObject.tp_richcompare and :c:member:~PyTypeObject.tp_hash are both NULL.
Default:
:c:data:PyBaseObject_Type uses :c:func:PyObject_GenericHash.
.. c:member:: ternaryfunc PyTypeObject.tp_call
.. corresponding-type-slot:: Py_tp_call
An optional pointer to a function that implements calling the object. This
should be NULL if the object is not callable. The signature is the same as
for :c:func:PyObject_Call::
PyObject *tp_call(PyObject *self, PyObject *args, PyObject *kwargs);
Inheritance:
This field is inherited by subtypes.
.. c:member:: reprfunc PyTypeObject.tp_str
.. corresponding-type-slot:: Py_tp_str
An optional pointer to a function that implements the built-in operation
:func:str. (Note that :class:str is a type now, and :func:str calls the
constructor for that type. This constructor calls :c:func:PyObject_Str to do
the actual work, and :c:func:PyObject_Str will call this handler.)
The signature is the same as for :c:func:PyObject_Str::
PyObject *tp_str(PyObject *self);
The function must return a string or a Unicode object. It should be a "friendly" string
representation of the object, as this is the representation that will be used,
among other things, by the :func:print function.
Inheritance:
This field is inherited by subtypes.
Default:
When this field is not set, :c:func:PyObject_Repr is called to return a string
representation.
.. c:member:: getattrofunc PyTypeObject.tp_getattro
.. corresponding-type-slot:: Py_tp_getattro
An optional pointer to the get-attribute function.
The signature is the same as for :c:func:PyObject_GetAttr::
PyObject *tp_getattro(PyObject *self, PyObject *attr);
It is usually convenient to set this field to :c:func:PyObject_GenericGetAttr,
which implements the normal way of looking for object attributes.
Inheritance:
Group: :c:member:~PyTypeObject.tp_getattr, :c:member:~PyTypeObject.tp_getattro
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_getattr: a subtype
inherits both :c:member:~PyTypeObject.tp_getattr and :c:member:~PyTypeObject.tp_getattro from its base type when
the subtype's :c:member:~PyTypeObject.tp_getattr and :c:member:~PyTypeObject.tp_getattro are both NULL.
Default:
:c:data:PyBaseObject_Type uses :c:func:PyObject_GenericGetAttr.
.. c:member:: setattrofunc PyTypeObject.tp_setattro
.. corresponding-type-slot:: Py_tp_setattro
An optional pointer to the function for setting and deleting attributes.
The signature is the same as for :c:func:PyObject_SetAttr::
int tp_setattro(PyObject *self, PyObject *attr, PyObject *value);
In addition, setting value to NULL to delete an attribute must be
supported. It is usually convenient to set this field to
:c:func:PyObject_GenericSetAttr, which implements the normal
way of setting object attributes.
Inheritance:
Group: :c:member:~PyTypeObject.tp_setattr, :c:member:~PyTypeObject.tp_setattro
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_setattr: a subtype
inherits both :c:member:~PyTypeObject.tp_setattr and :c:member:~PyTypeObject.tp_setattro from its base type when
the subtype's :c:member:~PyTypeObject.tp_setattr and :c:member:~PyTypeObject.tp_setattro are both NULL.
Default:
:c:data:PyBaseObject_Type uses :c:func:PyObject_GenericSetAttr.
.. c:member:: PyBufferProcs* PyTypeObject.tp_as_buffer
Pointer to an additional structure that contains fields relevant only to objects
which implement the buffer interface. These fields are documented in
:ref:buffer-structs.
Inheritance:
The :c:member:~PyTypeObject.tp_as_buffer field is not inherited,
but the contained fields are inherited individually.
.. c:member:: unsigned long PyTypeObject.tp_flags
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
:c:member:~PyTypeObject.tp_as_number, :c:member:~PyTypeObject.tp_as_sequence, :c:member:~PyTypeObject.tp_as_mapping, and
:c:member:~PyTypeObject.tp_as_buffer) 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 NULL value instead.
Inheritance:
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 :c:macro:Py_TPFLAGS_HAVE_GC flag bit is inherited together with
the :c:member:~PyTypeObject.tp_traverse and :c:member:~PyTypeObject.tp_clear fields, i.e. if the
:c:macro:Py_TPFLAGS_HAVE_GC flag bit is clear in the subtype and the
:c:member:~PyTypeObject.tp_traverse and :c:member:~PyTypeObject.tp_clear fields in the subtype exist and have
NULL values.
.. XXX are most flag bits really inherited individually?
Default:
:c:data:PyBaseObject_Type uses
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE.
Bit Masks:
.. c:namespace:: NULL
The following bit masks are currently defined; these can be ORed together using
the | operator to form the value of the :c:member:~PyTypeObject.tp_flags field. The macro
:c:func:PyType_HasFeature takes a type and a flags value, tp and f, and
checks whether tp->tp_flags & f is non-zero.
.. c:macro:: Py_TPFLAGS_HEAPTYPE
This bit is set when the type object itself is allocated on the heap, for
example, types created dynamically using :c:func:`PyType_FromSpec`. In this
case, the :c:member:`~PyObject.ob_type` 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). Heap types should also :ref:`support garbage collection <supporting-cycle-detection>`
as they can form a reference cycle with their own module object.
**Inheritance:**
???
.. c:macro:: Py_TPFLAGS_BASETYPE
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).
**Inheritance:**
???
.. c:macro:: Py_TPFLAGS_READY
This bit is set when the type object has been fully initialized by
:c:func:`PyType_Ready`.
**Inheritance:**
???
.. c:macro:: Py_TPFLAGS_READYING
This bit is set while :c:func:`PyType_Ready` is in the process of initializing
the type object.
**Inheritance:**
???
.. c:macro:: Py_TPFLAGS_HAVE_GC
This bit is set when the object supports garbage collection. If this bit
is set, memory for new instances (see :c:member:`~PyTypeObject.tp_alloc`)
must be allocated using :c:macro:`PyObject_GC_New` or
:c:func:`PyType_GenericAlloc` and deallocated (see
:c:member:`~PyTypeObject.tp_free`) using :c:func:`PyObject_GC_Del`. More
information in section :ref:`supporting-cycle-detection`.
**Inheritance:**
Group: :c:macro:`Py_TPFLAGS_HAVE_GC`, :c:member:`~PyTypeObject.tp_traverse`, :c:member:`~PyTypeObject.tp_clear`
The :c:macro:`Py_TPFLAGS_HAVE_GC` flag bit is inherited
together with the :c:member:`~PyTypeObject.tp_traverse` and :c:member:`~PyTypeObject.tp_clear`
fields, i.e. if the :c:macro:`Py_TPFLAGS_HAVE_GC` flag bit is
clear in the subtype and the :c:member:`~PyTypeObject.tp_traverse` and
:c:member:`~PyTypeObject.tp_clear` fields in the subtype exist and have ``NULL``
values.
.. c:macro:: Py_TPFLAGS_DEFAULT
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: :c:macro:`Py_TPFLAGS_HAVE_STACKLESS_EXTENSION`.
**Inheritance:**
???
.. c:macro:: Py_TPFLAGS_METHOD_DESCRIPTOR
This bit indicates that objects behave like unbound methods.
If this flag is set for ``type(meth)``, then:
- ``meth.__get__(obj, cls)(*args, **kwds)`` (with ``obj`` not None)
must be equivalent to ``meth(obj, *args, **kwds)``.
- ``meth.__get__(None, cls)(*args, **kwds)``
must be equivalent to ``meth(*args, **kwds)``.
This flag enables an optimization for typical method calls like
``obj.meth()``: it avoids creating a temporary "bound method" object for
``obj.meth``.
.. versionadded:: 3.8
**Inheritance:**
This flag is never inherited by types without the
:c:macro:`Py_TPFLAGS_IMMUTABLETYPE` flag set. For extension types, it is
inherited whenever :c:member:`~PyTypeObject.tp_descr_get` is inherited.
.. c:macro:: Py_TPFLAGS_MANAGED_DICT
This bit indicates that instances of the class have a :attr:`~object.__dict__`
attribute, and that the space for the dictionary is managed by the VM.
If this flag is set, :c:macro:`Py_TPFLAGS_HAVE_GC` must also be set.
The type traverse function must call :c:func:`PyObject_VisitManagedDict`
and its clear function must call :c:func:`PyObject_ClearManagedDict`.
.. versionadded:: 3.12
**Inheritance:**
This flag is inherited unless the
:c:member:`~PyTypeObject.tp_dictoffset` field is set in a superclass.
.. c:macro:: Py_TPFLAGS_MANAGED_WEAKREF
This bit indicates that instances of the class should be weakly
referenceable.
If this flag is set, :c:macro:`Py_TPFLAGS_HAVE_GC` must also be set.
.. versionadded:: 3.12
**Inheritance:**
This flag is inherited unless the
:c:member:`~PyTypeObject.tp_weaklistoffset` field is set in a superclass.
.. c:macro:: Py_TPFLAGS_PREHEADER
These bits indicate that the VM will manage some fields by storing them
before the object. Currently, this macro is equivalent to
:c:expr:`Py_TPFLAGS_MANAGED_DICT | Py_TPFLAGS_MANAGED_WEAKREF`.
This macro value relies on the implementation of the VM, so its value is not
stable and may change in a future version. Prefer using individual
flags instead.
.. versionadded:: 3.12
.. c:macro:: Py_TPFLAGS_ITEMS_AT_END
Only usable with variable-size types, i.e. ones with non-zero
:c:member:`~PyTypeObject.tp_itemsize`.
Indicates that the variable-sized portion of an instance of this type is
at the end of the instance's memory area, at an offset of
``Py_TYPE(obj)->tp_basicsize`` (which may be different in each
subclass).
When setting this flag, be sure that all superclasses either
use this memory layout, or are not variable-sized.
Python does not check this.
.. versionadded:: 3.12
**Inheritance:**
This flag is inherited.
.. XXX Document more flags here?
.. c:macro:: Py_TPFLAGS_LONG_SUBCLASS .. c:macro:: Py_TPFLAGS_LIST_SUBCLASS .. c:macro:: Py_TPFLAGS_TUPLE_SUBCLASS .. c:macro:: Py_TPFLAGS_BYTES_SUBCLASS .. c:macro:: Py_TPFLAGS_UNICODE_SUBCLASS .. c:macro:: Py_TPFLAGS_DICT_SUBCLASS .. c:macro:: Py_TPFLAGS_BASE_EXC_SUBCLASS .. c:macro:: Py_TPFLAGS_TYPE_SUBCLASS
Functions such as :c:func:`PyLong_Check` will call :c:func:`PyType_FastSubclass`
with one of these flags to quickly determine if a type is a subclass
of a built-in type; such specific checks are faster than a generic
check, like :c:func:`PyObject_IsInstance`. Custom types that inherit
from built-ins should have their :c:member:`~PyTypeObject.tp_flags`
set appropriately, or the code that interacts with such types
will behave differently depending on what kind of check is used.
.. c:macro:: Py_TPFLAGS_HAVE_FINALIZE
This bit is set when the :c:member:`~PyTypeObject.tp_finalize` slot is present in the
type structure.
.. versionadded:: 3.4
.. deprecated:: 3.8
This flag isn't necessary anymore, as the interpreter assumes the
:c:member:`~PyTypeObject.tp_finalize` slot is always present in the
type structure.
.. c:macro:: _Py_TPFLAGS_HAVE_VECTORCALL :no-typesetting:
.. c:macro:: Py_TPFLAGS_HAVE_VECTORCALL
This bit is set when the class implements
the :ref:`vectorcall protocol <vectorcall>`.
See :c:member:`~PyTypeObject.tp_vectorcall_offset` for details.
**Inheritance:**
This bit is inherited if :c:member:`~PyTypeObject.tp_call` is also
inherited.
.. versionadded:: 3.8 as ``_Py_TPFLAGS_HAVE_VECTORCALL``
.. versionchanged:: 3.9
Renamed to the current name, without the leading underscore.
The old provisional name is :term:`soft deprecated`.
.. versionchanged:: 3.12
This flag is now removed from a class when the class's
:py:meth:`~object.__call__` method is reassigned.
This flag can now be inherited by mutable classes.
.. c:macro:: Py_TPFLAGS_IMMUTABLETYPE
This bit is set for type objects that are immutable: type attributes cannot be set nor deleted.
:c:func:`PyType_Ready` automatically applies this flag to
:ref:`static types <static-types>`.
**Inheritance:**
This flag is not inherited.
.. versionadded:: 3.10
.. c:macro:: Py_TPFLAGS_DISALLOW_INSTANTIATION
Disallow creating instances of the type: set
:c:member:`~PyTypeObject.tp_new` to NULL and don't create the ``__new__``
key in the type dictionary.
The flag must be set before creating the type, not after. For example, it
must be set before :c:func:`PyType_Ready` is called on the type.
The flag is set automatically on :ref:`static types <static-types>` if
:c:member:`~PyTypeObject.tp_base` is NULL or ``&PyBaseObject_Type`` and
:c:member:`~PyTypeObject.tp_new` is NULL.
**Inheritance:**
This flag is not inherited.
However, subclasses will not be instantiable unless they provide a
non-NULL :c:member:`~PyTypeObject.tp_new` (which is only possible
via the C API).
.. note::
To disallow instantiating a class directly but allow instantiating
its subclasses (e.g. for an :term:`abstract base class`),
do not use this flag.
Instead, make :c:member:`~PyTypeObject.tp_new` only succeed for
subclasses.
.. versionadded:: 3.10
.. c:macro:: Py_TPFLAGS_MAPPING
This bit indicates that instances of the class may match mapping patterns
when used as the subject of a :keyword:`match` block. It is automatically
set when registering or subclassing :class:`collections.abc.Mapping`, and
unset when registering :class:`collections.abc.Sequence`.
.. note::
:c:macro:`Py_TPFLAGS_MAPPING` and :c:macro:`Py_TPFLAGS_SEQUENCE` are
mutually exclusive; it is an error to enable both flags simultaneously.
**Inheritance:**
This flag is inherited by types that do not already set
:c:macro:`Py_TPFLAGS_SEQUENCE`.
.. seealso:: :pep:`634` -- Structural Pattern Matching: Specification
.. versionadded:: 3.10
.. c:macro:: Py_TPFLAGS_SEQUENCE
This bit indicates that instances of the class may match sequence patterns
when used as the subject of a :keyword:`match` block. It is automatically
set when registering or subclassing :class:`collections.abc.Sequence`, and
unset when registering :class:`collections.abc.Mapping`.
.. note::
:c:macro:`Py_TPFLAGS_MAPPING` and :c:macro:`Py_TPFLAGS_SEQUENCE` are
mutually exclusive; it is an error to enable both flags simultaneously.
**Inheritance:**
This flag is inherited by types that do not already set
:c:macro:`Py_TPFLAGS_MAPPING`.
.. seealso:: :pep:`634` -- Structural Pattern Matching: Specification
.. versionadded:: 3.10
.. c:macro:: Py_TPFLAGS_VALID_VERSION_TAG
Internal. Do not set or unset this flag.
To indicate that a class has changed call :c:func:`PyType_Modified`
.. warning::
This flag is present in header files, but is not be used.
It will be removed in a future version of CPython
.. c:macro:: Py_TPFLAGS_HAVE_VERSION_TAG
This is a :term:`soft deprecated` macro that does nothing.
Historically, this would indicate that the
:c:member:`~PyTypeObject.tp_version_tag` field was available and
initialized.
.. c:macro:: Py_TPFLAGS_INLINE_VALUES
This bit indicates that instances of this type will have an "inline values"
array (containing the object's attributes) placed directly after the end
of the object.
This requires that :c:macro:`Py_TPFLAGS_HAVE_GC` is set.
**Inheritance:**
This flag is not inherited.
.. versionadded:: 3.13
.. c:macro:: Py_TPFLAGS_IS_ABSTRACT
This bit indicates that this is an abstract type and therefore cannot
be instantiated.
**Inheritance:**
This flag is not inherited.
.. seealso::
:mod:`abc`
.. c:macro:: Py_TPFLAGS_HAVE_STACKLESS_EXTENSION
Internal. Do not set or unset this flag.
Historically, this was a reserved flag for use in Stackless Python.
.. warning::
This flag is present in header files, but is not be used.
This may be removed in a future version of CPython.
.. c:member:: const char* PyTypeObject.tp_doc
.. corresponding-type-slot:: Py_tp_doc
An optional pointer to a NUL-terminated C string giving the docstring for this
type object. This is exposed as the :attr:~type.__doc__ attribute on the
type and instances of the type.
Inheritance:
This field is not inherited by subtypes.
.. c:member:: traverseproc PyTypeObject.tp_traverse
.. corresponding-type-slot:: Py_tp_traverse
An optional pointer to a traversal function for the garbage collector. This is
only used if the :c:macro:Py_TPFLAGS_HAVE_GC flag bit is set. The signature is::
int tp_traverse(PyObject *self, visitproc visit, void *arg);
More information about Python's garbage collection scheme can be found
in section :ref:supporting-cycle-detection.
The :c:member:~PyTypeObject.tp_traverse pointer is used by the garbage collector to detect
reference cycles. A typical implementation of a :c:member:~PyTypeObject.tp_traverse function
simply calls :c:func:Py_VISIT on each of the instance's members that are Python
objects that the instance owns. For example, this is function :c:func:!local_traverse from the
:mod:!_thread extension module::
static int
local_traverse(PyObject *op, visitproc visit, void *arg)
{
localobject *self = (localobject *) op;
Py_VISIT(self->args);
Py_VISIT(self->kw);
Py_VISIT(self->dict);
return 0;
}
Note that :c:func:Py_VISIT is called only on those members that can participate
in reference cycles. Although there is also a self->key member, it can only
be NULL or a Python string and therefore cannot be part of a reference cycle.
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 :mod:gc module's
:func:~gc.get_referents function will include it.
Heap types (:c:macro:Py_TPFLAGS_HEAPTYPE) must visit their type with::
Py_VISIT(Py_TYPE(self));
It is only needed since Python 3.9. To support Python 3.8 and older, this line must be conditional::
#if PY_VERSION_HEX >= 0x03090000
Py_VISIT(Py_TYPE(self));
#endif
If the :c:macro:Py_TPFLAGS_MANAGED_DICT bit is set in the
:c:member:~PyTypeObject.tp_flags field, the traverse function must call
:c:func:PyObject_VisitManagedDict like this::
PyObject_VisitManagedDict((PyObject*)self, visit, arg);
.. warning::
When implementing :c:member:~PyTypeObject.tp_traverse, only the
members that the instance owns (by having :term:strong references <strong reference> to them) must be
visited. For instance, if an object supports weak references via the
:c:member:~PyTypeObject.tp_weaklist slot, the pointer supporting
the linked list (what tp_weaklist points to) must not be
visited as the instance does not directly own the weak references to itself
(the weakreference list is there to support the weak reference machinery,
but the instance has no strong reference to the elements inside it, as they
are allowed to be removed even if the instance is still alive).
.. warning:: The traversal function must not have any side effects. It must not modify the reference counts of any Python objects nor create or destroy any Python objects.
Note that :c:func:Py_VISIT requires the visit and arg parameters to
:c:func:!local_traverse to have these specific names; don't name them just
anything.
Instances of :ref:heap-allocated types <heap-types> hold a reference to
their type. Their traversal function must therefore either visit
:c:func:Py_TYPE(self) <Py_TYPE>, or delegate this responsibility by
calling tp_traverse of another heap-allocated type (such as a
heap-allocated superclass).
If they do not, the type object may not be garbage-collected.
.. note::
The :c:member:`~PyTypeObject.tp_traverse` function can be called from any
thread.
.. versionchanged:: 3.9
Heap-allocated types are expected to visit ``Py_TYPE(self)`` in
``tp_traverse``. In earlier versions of Python, due to
`bug 40217 <https://bugs.python.org/issue40217>`_, doing this
may lead to crashes in subclasses.
Inheritance:
Group: :c:macro:Py_TPFLAGS_HAVE_GC, :c:member:~PyTypeObject.tp_traverse, :c:member:~PyTypeObject.tp_clear
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_clear and the
:c:macro:Py_TPFLAGS_HAVE_GC flag bit: the flag bit, :c:member:~PyTypeObject.tp_traverse, and
:c:member:~PyTypeObject.tp_clear are all inherited from the base type if they are all zero in
the subtype.
.. c:member:: inquiry PyTypeObject.tp_clear
.. corresponding-type-slot:: Py_tp_clear
An optional pointer to a clear function. The signature is::
int tp_clear(PyObject *);
The purpose of this function is to break reference cycles that are causing a
:term:cyclic isolate so that the objects can be safely destroyed. A
cleared object is a partially destroyed object; the object is not obligated
to satisfy design invariants held during normal use.
:c:member:!tp_clear does not need to delete references to objects that
can't participate in reference cycles, such as Python strings or Python
integers. However, it may be convenient to clear all references, and write
the type's :c:member:~PyTypeObject.tp_dealloc function to invoke
:c:member:!tp_clear to avoid code duplication. (Beware that
:c:member:!tp_clear might have already been called. Prefer calling
idempotent functions like :c:func:Py_CLEAR.)
Any non-trivial cleanup should be performed in
:c:member:~PyTypeObject.tp_finalize instead of :c:member:!tp_clear.
.. note::
If :c:member:`!tp_clear` fails to break a reference cycle then the
objects in the :term:`cyclic isolate` may remain indefinitely
uncollectable ("leak"). See :data:`gc.garbage`.
.. note::
Referents (direct and indirect) might have already been cleared; they are
not guaranteed to be in a consistent state.
.. note::
The :c:member:`~PyTypeObject.tp_clear` function can be called from any
thread.
.. note::
An object is not guaranteed to be automatically cleared before its
destructor (:c:member:`~PyTypeObject.tp_dealloc`) is called.
This function differs from the destructor
(:c:member:~PyTypeObject.tp_dealloc) in the following ways:
~PyTypeObject.tp_free).!tp_clear is called, other objects might still hold
references to the object being cleared. Because of this,
:c:member:!tp_clear must not deallocate the object's own memory
(:c:member:~PyTypeObject.tp_free). The destructor, on the other hand,
is only called when no (strong) references exist, and as such, must
safely destroy the object itself by deallocating it.!tp_clear might never be automatically called. An object's
destructor, on the other hand, will be automatically called some time
after the object becomes unreachable (i.e., either there are no references
to the object or the object is a member of a :term:cyclic isolate).No guarantees are made about when, if, or how often Python automatically clears an object, except:
cyclic isolate.~PyTypeObject.tp_finalize). (If
the finalizer resurrected the object, the object may or may not be
automatically finalized again before it is cleared.)cyclic isolate, Python will not
automatically clear it if any member of the cyclic isolate has not yet
been automatically finalized (:c:member:~PyTypeObject.tp_finalize).!tp_clear function have returned. This ensures that the act
of breaking a reference cycle does not invalidate the self pointer
while :c:member:!tp_clear is still executing.!tp_clear multiple times
concurrently.CPython currently only automatically clears objects as needed to break
reference cycles in a :term:cyclic isolate, but future versions might
clear objects regularly before their destruction.
Taken together, all :c:member:~PyTypeObject.tp_clear functions in the
system must combine to break all reference cycles. This is subtle, and if
in any doubt supply a :c:member:~PyTypeObject.tp_clear function. For
example, the tuple type does not implement a
:c:member:~PyTypeObject.tp_clear function, because it's possible to prove
that no reference cycle can be composed entirely of tuples. Therefore the
:c:member:~PyTypeObject.tp_clear functions of other types are responsible
for breaking any cycle containing a tuple. This isn't immediately obvious,
and there's rarely a good reason to avoid implementing
:c:member:~PyTypeObject.tp_clear.
Implementations of :c:member:~PyTypeObject.tp_clear should drop the instance's references to
those of its members that may be Python objects, and set its pointers to those
members to NULL, as in the following example::
static int
local_clear(PyObject *op)
{
localobject *self = (localobject *) op;
Py_CLEAR(self->key);
Py_CLEAR(self->args);
Py_CLEAR(self->kw);
Py_CLEAR(self->dict);
return 0;
}
The :c:func:Py_CLEAR macro should be used, because clearing references is
delicate: the reference to the contained object must not be released
(via :c:func:Py_DECREF) until
after the pointer to the contained object is set to NULL. This is because
releasing the reference 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 self again,
it's important that the pointer to the contained object be NULL at that time,
so that self knows the contained object can no longer be used. The
:c:func:Py_CLEAR macro performs the operations in a safe order.
If the :c:macro:Py_TPFLAGS_MANAGED_DICT bit is set in the
:c:member:~PyTypeObject.tp_flags field, the clear function must call
:c:func:PyObject_ClearManagedDict like this::
PyObject_ClearManagedDict((PyObject*)self);
More information about Python's garbage collection scheme can be found in
section :ref:supporting-cycle-detection.
Inheritance:
Group: :c:macro:Py_TPFLAGS_HAVE_GC, :c:member:~PyTypeObject.tp_traverse, :c:member:~PyTypeObject.tp_clear
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_traverse and the
:c:macro:Py_TPFLAGS_HAVE_GC flag bit: the flag bit, :c:member:~PyTypeObject.tp_traverse, and
:c:member:~PyTypeObject.tp_clear are all inherited from the base type if they are all zero in
the subtype.
.. seealso::
:ref:`life-cycle` for details about how this slot relates to other slots.
.. c:member:: richcmpfunc PyTypeObject.tp_richcompare
.. corresponding-type-slot:: Py_tp_richcompare
An optional pointer to the rich comparison function, whose signature is::
PyObject *tp_richcompare(PyObject *self, PyObject *other, int op);
The first parameter is guaranteed to be an instance of the type
that is defined by :c:type:PyTypeObject.
The function should return the result of the comparison (usually Py_True
or Py_False). If the comparison is undefined, it must return
Py_NotImplemented, if another error occurred it must return NULL and
set an exception condition.
The following constants are defined to be used as the third argument for
:c:member:~PyTypeObject.tp_richcompare and for :c:func:PyObject_RichCompare:
.. c:namespace:: NULL
+--------------------+------------+
| Constant | Comparison |
+====================+============+
| .. c:macro:: Py_LT | < |
+--------------------+------------+
| .. c:macro:: Py_LE | <= |
+--------------------+------------+
| .. c:macro:: Py_EQ | == |
+--------------------+------------+
| .. c:macro:: Py_NE | != |
+--------------------+------------+
| .. c:macro:: Py_GT | > |
+--------------------+------------+
| .. c:macro:: Py_GE | >= |
+--------------------+------------+
The following macro is defined to ease writing rich comparison functions:
.. c:macro:: Py_RETURN_RICHCOMPARE(VAL_A, VAL_B, op)
Return ``Py_True`` or ``Py_False`` from the function, depending on the
result of a comparison.
VAL_A and VAL_B must be orderable by C comparison operators (for example,
they may be C ints or floats). The third argument specifies the requested
operation, as for :c:func:`PyObject_RichCompare`.
The returned value is a new :term:`strong reference`.
On error, sets an exception and returns ``NULL`` from the function.
.. versionadded:: 3.7
Inheritance:
Group: :c:member:~PyTypeObject.tp_hash, :c:member:~PyTypeObject.tp_richcompare
This field is inherited by subtypes together with :c:member:~PyTypeObject.tp_hash:
a subtype inherits :c:member:~PyTypeObject.tp_richcompare and :c:member:~PyTypeObject.tp_hash when
the subtype's :c:member:~PyTypeObject.tp_richcompare and :c:member:~PyTypeObject.tp_hash are both
NULL.
Default:
:c:data:PyBaseObject_Type provides a :c:member:~PyTypeObject.tp_richcompare
implementation, which may be inherited. However, if only
:c:member:~PyTypeObject.tp_hash is defined, not even the inherited function is used
and instances of the type will not be able to participate in any
comparisons.
.. c:member:: Py_ssize_t PyTypeObject.tp_weaklistoffset
While this field is still supported, :c:macro:Py_TPFLAGS_MANAGED_WEAKREF
should be used instead, if at all possible.
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
:c:func:PyObject_ClearWeakRefs and the PyWeakref_* functions. The
instance structure needs to include a field of type :c:expr:PyObject* which is
initialized to NULL.
Do not confuse this field with :c:member:~PyTypeObject.tp_weaklist; that is the list head for
weak references to the type object itself.
It is an error to set both the :c:macro:Py_TPFLAGS_MANAGED_WEAKREF bit and
:c:member:~PyTypeObject.tp_weaklistoffset.
Inheritance:
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
:c:member:~PyTypeObject.tp_weaklistoffset, this should not be a problem.
Default:
If the :c:macro:Py_TPFLAGS_MANAGED_WEAKREF bit is set in the
:c:member:~PyTypeObject.tp_flags field, then
:c:member:~PyTypeObject.tp_weaklistoffset will be set to a negative value,
to indicate that it is unsafe to use this field.
.. c:member:: getiterfunc PyTypeObject.tp_iter
.. corresponding-type-slot:: Py_tp_iter
An optional pointer to a function that returns an :term:iterator for the
object. Its presence normally signals that the instances of this type are
:term:iterable (although sequences may be iterable without this function).
This function has the same signature as :c:func:PyObject_GetIter::
PyObject *tp_iter(PyObject *self);
Inheritance:
This field is inherited by subtypes.
.. c:member:: iternextfunc PyTypeObject.tp_iternext
.. corresponding-type-slot:: Py_tp_iternext
An optional pointer to a function that returns the next item in an
:term:iterator. The signature is::
PyObject *tp_iternext(PyObject *self);
When the iterator is exhausted, it must return NULL; a :exc:StopIteration
exception may or may not be set. When another error occurs, it must return
NULL too. Its presence signals that the instances of this type are
iterators.
Iterator types should also define the :c:member:~PyTypeObject.tp_iter function, and that
function should return the iterator instance itself (not a new iterator
instance).
This function has the same signature as :c:func:PyIter_Next.
Inheritance:
This field is inherited by subtypes.
.. c:member:: struct PyMethodDef* PyTypeObject.tp_methods
.. corresponding-type-slot:: Py_tp_methods
An optional pointer to a static NULL-terminated array of :c:type:PyMethodDef
structures, declaring regular methods of this type.
For each entry in the array, an entry is added to the type's dictionary (see
:c:member:~PyTypeObject.tp_dict below) containing a method descriptor.
Inheritance:
This field is not inherited by subtypes (methods are inherited through a different mechanism).
.. c:member:: struct PyMemberDef* PyTypeObject.tp_members
.. corresponding-type-slot:: Py_tp_members
An optional pointer to a static NULL-terminated array of :c:type:PyMemberDef
structures, declaring regular data members (fields or slots) of instances of
this type.
For each entry in the array, an entry is added to the type's dictionary (see
:c:member:~PyTypeObject.tp_dict below) containing a member descriptor.
Inheritance:
This field is not inherited by subtypes (members are inherited through a different mechanism).
.. c:member:: struct PyGetSetDef* PyTypeObject.tp_getset
.. corresponding-type-slot:: Py_tp_getset
An optional pointer to a static NULL-terminated array of :c:type:PyGetSetDef
structures, declaring computed attributes of instances of this type.
For each entry in the array, an entry is added to the type's dictionary (see
:c:member:~PyTypeObject.tp_dict below) containing a getset descriptor.
Inheritance:
This field is not inherited by subtypes (computed attributes are inherited through a different mechanism).
.. c:member:: PyTypeObject* PyTypeObject.tp_base
.. corresponding-type-slot:: Py_tp_base
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.
.. note::
.. from Modules/xxmodule.c
Slot initialization is subject to the rules of initializing globals.
C99 requires the initializers to be "address constants". Function
designators like :c:func:`PyType_GenericNew`, with implicit conversion
to a pointer, are valid C99 address constants.
However, the unary '&' operator applied to a non-static variable
like :c:data:`PyBaseObject_Type` is not required to produce an address
constant. Compilers may support this (gcc does), MSVC does not.
Both compilers are strictly standard conforming in this particular
behavior.
Consequently, :c:member:`~PyTypeObject.tp_base` should be set in
the extension module's init function.
Inheritance:
This field is not inherited by subtypes (obviously).
Default:
This field defaults to &PyBaseObject_Type (which to Python
programmers is known as the type :class:object).
.. c:member:: PyObject* PyTypeObject.tp_dict
The type's dictionary is stored here by :c:func:PyType_Ready.
This field should normally be initialized to NULL before PyType_Ready is
called; it may also be initialized to a dictionary containing initial attributes
for the type. Once :c:func:PyType_Ready 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 :meth:~object.__add__). Once
initialization for the type has finished, this field should be
treated as read-only.
Some types may not store their dictionary in this slot.
Use :c:func:PyType_GetDict to retrieve the dictionary for an arbitrary
type.
.. versionchanged:: 3.12
Internals detail: For static builtin types, this is always ``NULL``.
Instead, the dict for such types is stored on ``PyInterpreterState``.
Use :c:func:`PyType_GetDict` to get the dict for an arbitrary type.
Inheritance:
This field is not inherited by subtypes (though the attributes defined in here are inherited through a different mechanism).
Default:
If this field is NULL, :c:func:PyType_Ready will assign a new
dictionary to it.
.. warning::
It is not safe to use :c:func:`PyDict_SetItem` on or otherwise modify
:c:member:`~PyTypeObject.tp_dict` with the dictionary C-API.
.. c:member:: descrgetfunc PyTypeObject.tp_descr_get
.. corresponding-type-slot:: Py_tp_descr_get
An optional pointer to a "descriptor get" function.
The function signature is::
PyObject * tp_descr_get(PyObject *self, PyObject *obj, PyObject *type);
.. XXX explain more?
Inheritance:
This field is inherited by subtypes.
.. c:member:: descrsetfunc PyTypeObject.tp_descr_set
.. corresponding-type-slot:: Py_tp_descr_set
An optional pointer to a function for setting and deleting a descriptor's value.
The function signature is::
int tp_descr_set(PyObject *self, PyObject *obj, PyObject *value);
The value argument is set to NULL to delete the value.
.. XXX explain more?
Inheritance:
This field is inherited by subtypes.
.. c:member:: Py_ssize_t PyTypeObject.tp_dictoffset
While this field is still supported, :c:macro:Py_TPFLAGS_MANAGED_DICT should be
used instead, if at all possible.
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
:c:func:PyObject_GenericGetAttr.
Do not confuse this field with :c:member:~PyTypeObject.tp_dict; that is the dictionary for
attributes of the type object itself.
The value specifies the offset of the dictionary from the start of the instance structure.
The :c:member:~PyTypeObject.tp_dictoffset should be regarded as write-only.
To get the pointer to the dictionary call :c:func:PyObject_GenericGetDict.
Calling :c:func:PyObject_GenericGetDict may need to allocate memory for the
dictionary, so it is may be more efficient to call :c:func:PyObject_GetAttr
when accessing an attribute on the object.
It is an error to set both the :c:macro:Py_TPFLAGS_MANAGED_DICT bit and
:c:member:~PyTypeObject.tp_dictoffset.
Inheritance:
This field is inherited by subtypes. A subtype should not override this offset;
doing so could be unsafe, if C code tries to access the dictionary at the
previous offset.
To properly support inheritance, use :c:macro:Py_TPFLAGS_MANAGED_DICT.
Default:
This slot has no default. For :ref:static types <static-types>, if the
field is NULL then no :attr:~object.__dict__ gets created for instances.
If the :c:macro:Py_TPFLAGS_MANAGED_DICT bit is set in the
:c:member:~PyTypeObject.tp_flags field, then
:c:member:~PyTypeObject.tp_dictoffset will be set to -1, to indicate
that it is unsafe to use this field.
.. c:member:: initproc PyTypeObject.tp_init
.. corresponding-type-slot:: Py_tp_init
An optional pointer to an instance initialization function.
This function corresponds to the :meth:~object.__init__ method of classes. Like
:meth:!__init__, it is possible to create an instance without calling
:meth:!__init__, and it is possible to reinitialize an instance by calling its
:meth:!__init__ method again.
The function signature is::
int tp_init(PyObject *self, PyObject *args, PyObject *kwds);
The self argument is the instance to be initialized; the args and kwds
arguments represent positional and keyword arguments of the call to
:meth:~object.__init__.
The :c:member:~PyTypeObject.tp_init function, if not NULL, is called when an instance is
created normally by calling its type, after the type's :c:member:~PyTypeObject.tp_new function
has returned an instance of the type. If the :c:member:~PyTypeObject.tp_new function returns an
instance of some other type that is not a subtype of the original type, no
:c:member:~PyTypeObject.tp_init function is called; if :c:member:~PyTypeObject.tp_new returns an instance of a
subtype of the original type, the subtype's :c:member:~PyTypeObject.tp_init is called.
Returns 0 on success, -1 and sets an exception on error.
Inheritance:
This field is inherited by subtypes.
Default:
For :ref:static types <static-types> this field does not have a default.
.. c:member:: allocfunc PyTypeObject.tp_alloc
.. corresponding-type-slot:: Py_tp_alloc
An optional pointer to an instance allocation function.
The function signature is::
PyObject *tp_alloc(PyTypeObject *self, Py_ssize_t nitems);
Inheritance:
Static subtypes inherit this slot, which will be
:c:func:PyType_GenericAlloc if inherited from :class:object.
:ref:Heap subtypes <heap-types> do not inherit this slot.
Default:
For heap subtypes, this field is always set to
:c:func:PyType_GenericAlloc.
For static subtypes, this slot is inherited (see above).
.. c:member:: newfunc PyTypeObject.tp_new
.. corresponding-type-slot:: Py_tp_new
An optional pointer to an instance creation function.
The function signature is::
PyObject *tp_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds);
The subtype argument is the type of the object being created; the args and
kwds arguments represent positional and keyword arguments of the call to the
type. Note that subtype doesn't have to equal the type whose :c:member:~PyTypeObject.tp_new
function is called; it may be a subtype of that type (but not an unrelated
type).
The :c:member:~PyTypeObject.tp_new function should call subtype->tp_alloc(subtype, nitems)
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 :c:member:~PyTypeObject.tp_init handler. A good
rule of thumb is that for immutable types, all initialization should take place
in :c:member:~PyTypeObject.tp_new, while for mutable types, most initialization should be
deferred to :c:member:~PyTypeObject.tp_init.
Set the :c:macro:Py_TPFLAGS_DISALLOW_INSTANTIATION flag to disallow creating
instances of the type in Python.
Inheritance:
This field is inherited by subtypes, except it is not inherited by
:ref:static types <static-types> whose :c:member:~PyTypeObject.tp_base
is NULL or &PyBaseObject_Type.
Default:
For :ref:static types <static-types> this field has no default.
This means if the slot is defined as NULL, the type cannot be called
to create new instances; presumably there is some other way to create
instances, like a factory function.
.. c:member:: freefunc PyTypeObject.tp_free
.. corresponding-type-slot:: Py_tp_free
An optional pointer to an instance deallocation function. Its signature is::
void tp_free(void *self);
This function must free the memory allocated by
:c:member:~PyTypeObject.tp_alloc.
Inheritance:
Static subtypes inherit this slot, which will be :c:func:PyObject_Free if
inherited from :class:object. Exception: If the type supports garbage
collection (i.e., the :c:macro:Py_TPFLAGS_HAVE_GC flag is set in
:c:member:~PyTypeObject.tp_flags) and it would inherit
:c:func:PyObject_Free, then this slot is not inherited but instead defaults
to :c:func:PyObject_GC_Del.
:ref:Heap subtypes <heap-types> do not inherit this slot.
Default:
For :ref:heap subtypes <heap-types>, this slot defaults to a deallocator suitable to match
:c:func:PyType_GenericAlloc and the value of the
:c:macro:Py_TPFLAGS_HAVE_GC flag.
For static subtypes, this slot is inherited (see above).
.. c:member:: inquiry PyTypeObject.tp_is_gc
.. corresponding-type-slot:: Py_tp_is_gc
An optional pointer to a function called by the garbage collector.
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
:c:member:~PyTypeObject.tp_flags field, and check the :c:macro:Py_TPFLAGS_HAVE_GC 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 1 for a collectible instance, and
0 for a non-collectible instance. The signature is::
int tp_is_gc(PyObject *self);
(The only example of this are types themselves. The metatype,
:c:data:PyType_Type, defines this function to distinguish between statically
and :ref:dynamically allocated types <heap-types>.)
Inheritance:
This field is inherited by subtypes.
Default:
This slot has no default. If this field is NULL,
:c:macro:Py_TPFLAGS_HAVE_GC is used as the functional equivalent.
.. c:member:: PyObject* PyTypeObject.tp_bases
.. corresponding-type-slot:: Py_tp_bases
Tuple of base types.
This field should be set to NULL and treated as read-only.
Python will fill it in when the type is :c:func:initialized <PyType_Ready>.
For dynamically created classes, the :c:data:Py_tp_bases
:c:type:slot <PyType_Slot> can be used instead of the bases argument
of :c:func:PyType_FromSpecWithBases.
The argument form is preferred.
.. warning::
Multiple inheritance does not work well for statically defined types.
If you set ``tp_bases`` to a tuple, Python will not raise an error,
but some slots will only be inherited from the first base.
Inheritance:
This field is not inherited.
.. c:member:: PyObject* PyTypeObject.tp_mro
Tuple containing the expanded set of base types, starting with the type itself
and ending with :class:object, in Method Resolution Order.
This field should be set to NULL and treated as read-only.
Python will fill it in when the type is :c:func:initialized <PyType_Ready>.
Inheritance:
This field is not inherited; it is calculated fresh by
:c:func:PyType_Ready.
.. c:member:: PyObject* PyTypeObject.tp_cache
Unused. Internal use only.
Inheritance:
This field is not inherited.
.. c:member:: void* PyTypeObject.tp_subclasses
A collection of subclasses. Internal use only. May be an invalid pointer.
To get a list of subclasses, call the Python method
:py:meth:~type.__subclasses__.
.. versionchanged:: 3.12
For some types, this field does not hold a valid :c:expr:`PyObject*`.
The type was changed to :c:expr:`void*` to indicate this.
Inheritance:
This field is not inherited.
.. c:member:: PyObject* PyTypeObject.tp_weaklist
Weak reference list head, for weak references to this type object. Not inherited. Internal use only.
.. versionchanged:: 3.12
Internals detail: For the static builtin types this is always ``NULL``,
even if weakrefs are added. Instead, the weakrefs for each are stored
on ``PyInterpreterState``. Use the public C-API or the internal
``_PyObject_GET_WEAKREFS_LISTPTR()`` macro to avoid the distinction.
Inheritance:
This field is not inherited.
.. c:member:: destructor PyTypeObject.tp_del
.. corresponding-type-slot:: Py_tp_del
This field is deprecated. Use :c:member:~PyTypeObject.tp_finalize instead.
.. c:member:: unsigned int PyTypeObject.tp_version_tag
Used to index into the method cache. Internal use only.
Inheritance:
This field is not inherited.
.. c:member:: destructor PyTypeObject.tp_finalize
.. corresponding-type-slot:: Py_tp_finalize
An optional pointer to an instance finalization function. This is the C
implementation of the :meth:~object.__del__ special method. Its signature
is::
void tp_finalize(PyObject *self);
The primary purpose of finalization is to perform any non-trivial cleanup that must be performed before the object is destroyed, while the object and any other objects it directly or indirectly references are still in a consistent state. The finalizer is allowed to execute arbitrary Python code.
Before Python automatically finalizes an object, some of the object's direct
or indirect referents might have themselves been automatically finalized.
However, none of the referents will have been automatically cleared
(:c:member:~PyTypeObject.tp_clear) yet.
Other non-finalized objects might still be using a finalized object, so the finalizer must leave the object in a sane state (e.g., invariants are still met).
.. note::
After Python automatically finalizes an object, Python might start
automatically clearing (:c:member:`~PyTypeObject.tp_clear`) the object
and its referents (direct and indirect). Cleared objects are not
guaranteed to be in a consistent state; a finalized object must be able
to tolerate cleared referents.
.. note::
An object is not guaranteed to be automatically finalized before its
destructor (:c:member:`~PyTypeObject.tp_dealloc`) is called. It is
recommended to call :c:func:`PyObject_CallFinalizerFromDealloc` at the
beginning of :c:member:`!tp_dealloc` to guarantee that the object is
always finalized before destruction.
.. note::
The :c:member:`~PyTypeObject.tp_finalize` function can be called from any
thread, although the :term:`GIL` will be held.
.. note::
The :c:member:`!tp_finalize` function can be called during shutdown,
after some global variables have been deleted. See the documentation of
the :meth:`~object.__del__` method for details.
When Python finalizes an object, it behaves like the following algorithm:
#. Python might mark the object as finalized. Currently, Python always
marks objects whose type supports garbage collection (i.e., the
:c:macro:Py_TPFLAGS_HAVE_GC flag is set in
:c:member:~PyTypeObject.tp_flags) and never marks other types of
objects; this might change in a future version.
#. If the object is not marked as finalized and its
:c:member:!tp_finalize finalizer function is non-NULL, the
finalizer function is called.
#. If the finalizer function was called and the finalizer made the object
reachable (i.e., there is a reference to the object and it is not a
member of a :term:cyclic isolate), then the finalizer is said to have
resurrected the object. It is unspecified whether the finalizer can
also resurrect the object by adding a new reference to the object that
does not make it reachable, i.e., the object is (still) a member of a
cyclic isolate.
#. If the finalizer resurrected the object, the object's pending destruction
is canceled and the object's finalized mark might be removed if
present. Currently, Python never removes the finalized mark; this
might change in a future version.
Automatic finalization refers to any finalization performed by Python
except via calls to :c:func:PyObject_CallFinalizer or
:c:func:PyObject_CallFinalizerFromDealloc. No guarantees are made about
when, if, or how often an object is automatically finalized, except:
cyclic isolate.Py_TPFLAGS_HAVE_GC flag is not set. Such objects can still be
manually finalized by calling :c:func:PyObject_CallFinalizer or
:c:func:PyObject_CallFinalizerFromDealloc.cyclic isolate concurrently.~PyTypeObject.tp_clear) the object.cyclic isolate, Python will not
automatically finalize it after automatically clearing (see
:c:member:~PyTypeObject.tp_clear) any other member.cyclic isolate before it automatically clears (see
:c:member:~PyTypeObject.tp_clear) any of them.~PyTypeObject.tp_clear), it will automatically finalize the
object first.Python currently only automatically finalizes objects that are members of a
:term:cyclic isolate, but future versions might finalize objects regularly
before their destruction.
To manually finalize an object, do not call this function directly; call
:c:func:PyObject_CallFinalizer or
:c:func:PyObject_CallFinalizerFromDealloc instead.
:c:member:~PyTypeObject.tp_finalize should leave the current exception
status unchanged. The recommended way to write a non-trivial finalizer is
to back up the exception at the beginning by calling
:c:func:PyErr_GetRaisedException and restore the exception at the end by
calling :c:func:PyErr_SetRaisedException. If an exception is encountered
in the middle of the finalizer, log and clear it with
:c:func:PyErr_WriteUnraisable or :c:func:PyErr_FormatUnraisable. For
example::
static void
foo_finalize(PyObject *self)
{
// Save the current exception, if any.
PyObject *exc = PyErr_GetRaisedException();
// ...
if (do_something_that_might_raise() != success_indicator) {
PyErr_WriteUnraisable(self);
goto done;
}
done:
// Restore the saved exception. This silently discards any exception
// raised above, so be sure to call PyErr_WriteUnraisable first if
// necessary.
PyErr_SetRaisedException(exc);
}
Inheritance:
This field is inherited by subtypes.
.. versionadded:: 3.4
.. versionchanged:: 3.8
Before version 3.8 it was necessary to set the
:c:macro:`Py_TPFLAGS_HAVE_FINALIZE` flags bit in order for this field to be
used. This is no longer required.
.. seealso::
* :pep:`442`: "Safe object finalization"
* :ref:`life-cycle` for details about how this slot relates to other
slots.
* :c:func:`PyObject_CallFinalizer`
* :c:func:`PyObject_CallFinalizerFromDealloc`
.. c:member:: vectorcallfunc PyTypeObject.tp_vectorcall
.. corresponding-type-slot:: Py_tp_vectorcall
A :ref:vectorcall function <vectorcall> to use for calls of this type
object (rather than instances).
In other words, tp_vectorcall can be used to optimize type.__call__,
which typically returns a new instance of type.
As with any vectorcall function, if tp_vectorcall is NULL,
the tp_call protocol (Py_TYPE(type)->tp_call) is used instead.
.. note::
The :ref:`vectorcall protocol <vectorcall>` requires that the vectorcall
function has the same behavior as the corresponding ``tp_call``.
This means that ``type->tp_vectorcall`` must match the behavior of
``Py_TYPE(type)->tp_call``.
Specifically, if *type* uses the default metaclass,
``type->tp_vectorcall`` must behave the same as
:c:expr:`PyType_Type->tp_call`, which:
- calls ``type->tp_new``,
- if the result is a subclass of *type*, calls ``type->tp_init``
on the result of ``tp_new``, and
- returns the result of ``tp_new``.
Typically, ``tp_vectorcall`` is overridden to optimize this process
for specific :c:member:`~PyTypeObject.tp_new` and
:c:member:`~PyTypeObject.tp_init`.
When doing this for user-subclassable types, note that both can be
overridden (using :py:func:`~object.__new__` and
:py:func:`~object.__init__`, respectively).
Inheritance:
This field is never inherited.
.. versionadded:: 3.9 (the field exists since 3.8 but it's only used since 3.9)
.. c:member:: unsigned char PyTypeObject.tp_watched
Internal. Do not use.
.. versionadded:: 3.12
.. _static-types:
Traditionally, types defined in C code are static, that is,
a static :c:type:PyTypeObject structure is defined directly in code
and initialized using :c:func:PyType_Ready.
This results in types that are limited relative to types defined in Python:
sub-interpreters <sub-interpreter-support>, so they should not
include any subinterpreter-specific state.Also, since :c:type:PyTypeObject is only part of the :ref:Limited API <limited-c-api> as an opaque struct, any extension modules using static types must be
compiled for a specific Python minor version.
.. _heap-types:
An alternative to :ref:static types <static-types> is heap-allocated types,
or heap types for short, which correspond closely to classes created by
Python's class statement. Heap types have the :c:macro:Py_TPFLAGS_HEAPTYPE
flag set.
This is done by filling a :c:type:PyType_Spec structure and calling
:c:func:PyType_FromSpec, :c:func:PyType_FromSpecWithBases,
:c:func:PyType_FromModuleAndSpec, or :c:func:PyType_FromMetaclass.
.. _number-structs:
.. c:type:: PyNumberMethods
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 :ref:number section.
.. XXX Drop the definition?
Here is the structure definition::
typedef struct {
binaryfunc nb_add;
binaryfunc nb_subtract;
binaryfunc nb_multiply;
binaryfunc nb_remainder;
binaryfunc nb_divmod;
ternaryfunc nb_power;
unaryfunc nb_negative;
unaryfunc nb_positive;
unaryfunc nb_absolute;
inquiry nb_bool;
unaryfunc nb_invert;
binaryfunc nb_lshift;
binaryfunc nb_rshift;
binaryfunc nb_and;
binaryfunc nb_xor;
binaryfunc nb_or;
unaryfunc nb_int;
void *nb_reserved;
unaryfunc nb_float;
binaryfunc nb_inplace_add;
binaryfunc nb_inplace_subtract;
binaryfunc nb_inplace_multiply;
binaryfunc nb_inplace_remainder;
ternaryfunc nb_inplace_power;
binaryfunc nb_inplace_lshift;
binaryfunc nb_inplace_rshift;
binaryfunc nb_inplace_and;
binaryfunc nb_inplace_xor;
binaryfunc nb_inplace_or;
binaryfunc nb_floor_divide;
binaryfunc nb_true_divide;
binaryfunc nb_inplace_floor_divide;
binaryfunc nb_inplace_true_divide;
unaryfunc nb_index;
binaryfunc nb_matrix_multiply;
binaryfunc nb_inplace_matrix_multiply;
} PyNumberMethods;
.. note::
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
``Py_NotImplemented``, if another error occurred they must return ``NULL``
and set an exception.
.. note::
The :c:member:`~PyNumberMethods.nb_reserved` field should always be ``NULL``. It
was previously called :c:member:`!nb_long`, and was renamed in
Python 3.0.1.
.. c:member:: binaryfunc PyNumberMethods.nb_add
.. corresponding-type-slot:: Py_nb_add
.. c:member:: binaryfunc PyNumberMethods.nb_subtract
.. corresponding-type-slot:: Py_nb_subtract
.. c:member:: binaryfunc PyNumberMethods.nb_multiply
.. corresponding-type-slot:: Py_nb_multiply
.. c:member:: binaryfunc PyNumberMethods.nb_remainder
.. corresponding-type-slot:: Py_nb_remainder
.. c:member:: binaryfunc PyNumberMethods.nb_divmod
.. corresponding-type-slot:: Py_nb_divmod
.. c:member:: ternaryfunc PyNumberMethods.nb_power
.. corresponding-type-slot:: Py_nb_power
.. c:member:: unaryfunc PyNumberMethods.nb_negative
.. corresponding-type-slot:: Py_nb_negative
.. c:member:: unaryfunc PyNumberMethods.nb_positive
.. corresponding-type-slot:: Py_nb_positive
.. c:member:: unaryfunc PyNumberMethods.nb_absolute
.. corresponding-type-slot:: Py_nb_absolute
.. c:member:: inquiry PyNumberMethods.nb_bool
.. corresponding-type-slot:: Py_nb_bool
.. c:member:: unaryfunc PyNumberMethods.nb_invert
.. corresponding-type-slot:: Py_nb_invert
.. c:member:: binaryfunc PyNumberMethods.nb_lshift
.. corresponding-type-slot:: Py_nb_lshift
.. c:member:: binaryfunc PyNumberMethods.nb_rshift
.. corresponding-type-slot:: Py_nb_rshift
.. c:member:: binaryfunc PyNumberMethods.nb_and
.. corresponding-type-slot:: Py_nb_and
.. c:member:: binaryfunc PyNumberMethods.nb_xor
.. corresponding-type-slot:: Py_nb_xor
.. c:member:: binaryfunc PyNumberMethods.nb_or
.. corresponding-type-slot:: Py_nb_or
.. c:member:: unaryfunc PyNumberMethods.nb_int
.. corresponding-type-slot:: Py_nb_int
.. c:member:: void *PyNumberMethods.nb_reserved
.. c:member:: unaryfunc PyNumberMethods.nb_float
.. corresponding-type-slot:: Py_nb_float
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_add
.. corresponding-type-slot:: Py_nb_inplace_add
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_subtract
.. corresponding-type-slot:: Py_nb_inplace_subtract
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_multiply
.. corresponding-type-slot:: Py_nb_inplace_multiply
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_remainder
.. corresponding-type-slot:: Py_nb_inplace_remainder
.. c:member:: ternaryfunc PyNumberMethods.nb_inplace_power
.. corresponding-type-slot:: Py_nb_inplace_power
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_lshift
.. corresponding-type-slot:: Py_nb_inplace_lshift
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_rshift
.. corresponding-type-slot:: Py_nb_inplace_rshift
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_and
.. corresponding-type-slot:: Py_nb_inplace_and
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_xor
.. corresponding-type-slot:: Py_nb_inplace_xor
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_or
.. corresponding-type-slot:: Py_nb_inplace_or
.. c:member:: binaryfunc PyNumberMethods.nb_floor_divide
.. corresponding-type-slot:: Py_nb_floor_divide
.. c:member:: binaryfunc PyNumberMethods.nb_true_divide
.. corresponding-type-slot:: Py_nb_true_divide
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_floor_divide
.. corresponding-type-slot:: Py_nb_inplace_floor_divide
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_true_divide
.. corresponding-type-slot:: Py_nb_inplace_true_divide
.. c:member:: unaryfunc PyNumberMethods.nb_index
.. corresponding-type-slot:: Py_nb_index
.. c:member:: binaryfunc PyNumberMethods.nb_matrix_multiply
.. corresponding-type-slot:: Py_nb_matrix_multiply
.. c:member:: binaryfunc PyNumberMethods.nb_inplace_matrix_multiply
.. corresponding-type-slot:: Py_nb_inplace_matrix_multiply
.. _mapping-structs:
.. c:type:: PyMappingMethods
This structure holds pointers to the functions which an object uses to implement the mapping protocol. It has three members:
.. c:member:: lenfunc PyMappingMethods.mp_length
.. corresponding-type-slot:: Py_mp_length
This function is used by :c:func:PyMapping_Size and
:c:func:PyObject_Size, and has the same signature. This slot may be set to
NULL if the object has no defined length.
.. c:member:: binaryfunc PyMappingMethods.mp_subscript
.. corresponding-type-slot:: Py_mp_subscript
This function is used by :c:func:PyObject_GetItem and
:c:func:PySequence_GetSlice, and has the same signature as
:c:func:!PyObject_GetItem. This slot must be filled for the
:c:func:PyMapping_Check function to return 1, it can be NULL
otherwise.
.. c:member:: objobjargproc PyMappingMethods.mp_ass_subscript
.. corresponding-type-slot:: Py_mp_ass_subscript
This function is used by :c:func:PyObject_SetItem,
:c:func:PyObject_DelItem, :c:func:PySequence_SetSlice and
:c:func:PySequence_DelSlice. It has the same signature as
:c:func:!PyObject_SetItem, but v can also be set to NULL to delete
an item. If this slot is NULL, the object does not support item
assignment and deletion.
.. _sequence-structs:
.. c:type:: PySequenceMethods
This structure holds pointers to the functions which an object uses to implement the sequence protocol.
.. c:member:: lenfunc PySequenceMethods.sq_length
.. corresponding-type-slot:: Py_sq_length
This function is used by :c:func:PySequence_Size and
:c:func:PyObject_Size, and has the same signature. It is also used for
handling negative indices via the :c:member:~PySequenceMethods.sq_item
and the :c:member:~PySequenceMethods.sq_ass_item slots.
.. c:member:: binaryfunc PySequenceMethods.sq_concat
.. corresponding-type-slot:: Py_sq_concat
This function is used by :c:func:PySequence_Concat and has the same
signature. It is also used by the + operator, after trying the numeric
addition via the :c:member:~PyNumberMethods.nb_add slot.
.. c:member:: ssizeargfunc PySequenceMethods.sq_repeat
.. corresponding-type-slot:: Py_sq_repeat
This function is used by :c:func:PySequence_Repeat and has the same
signature. It is also used by the * operator, after trying numeric
multiplication via the :c:member:~PyNumberMethods.nb_multiply slot.
.. c:member:: ssizeargfunc PySequenceMethods.sq_item
.. corresponding-type-slot:: Py_sq_item
This function is used by :c:func:PySequence_GetItem and has the same
signature. It is also used by :c:func:PyObject_GetItem, after trying
the subscription via the :c:member:~PyMappingMethods.mp_subscript slot.
This slot must be filled for the :c:func:PySequence_Check
function to return 1, it can be NULL otherwise.
Negative indexes are handled as follows: if the :c:member:~PySequenceMethods.sq_length slot is
filled, it is called and the sequence length is used to compute a positive
index which is passed to :c:member:~PySequenceMethods.sq_item. If :c:member:!sq_length is NULL,
the index is passed as is to the function.
.. c:member:: ssizeobjargproc PySequenceMethods.sq_ass_item
.. corresponding-type-slot:: Py_sq_ass_item
This function is used by :c:func:PySequence_SetItem and has the same
signature. It is also used by :c:func:PyObject_SetItem and
:c:func:PyObject_DelItem, after trying the item assignment and deletion
via the :c:member:~PyMappingMethods.mp_ass_subscript slot.
This slot may be left to NULL if the object does not support
item assignment and deletion.
.. c:member:: objobjproc PySequenceMethods.sq_contains
.. corresponding-type-slot:: Py_sq_contains
This function may be used by :c:func:PySequence_Contains and has the same
signature. This slot may be left to NULL, in this case
:c:func:!PySequence_Contains simply traverses the sequence until it
finds a match.
.. c:member:: binaryfunc PySequenceMethods.sq_inplace_concat
.. corresponding-type-slot:: Py_sq_inplace_concat
This function is used by :c:func:PySequence_InPlaceConcat and has the same
signature. It should modify its first operand, and return it. This slot
may be left to NULL, in this case :c:func:!PySequence_InPlaceConcat
will fall back to :c:func:PySequence_Concat. It is also used by the
augmented assignment +=, after trying numeric in-place addition
via the :c:member:~PyNumberMethods.nb_inplace_add slot.
.. c:member:: ssizeargfunc PySequenceMethods.sq_inplace_repeat
.. corresponding-type-slot:: Py_sq_inplace_repeat
This function is used by :c:func:PySequence_InPlaceRepeat and has the same
signature. It should modify its first operand, and return it. This slot
may be left to NULL, in this case :c:func:!PySequence_InPlaceRepeat
will fall back to :c:func:PySequence_Repeat. It is also used by the
augmented assignment *=, after trying numeric in-place multiplication
via the :c:member:~PyNumberMethods.nb_inplace_multiply slot.
.. _buffer-structs:
.. c:type:: PyBufferProcs
This structure holds pointers to the functions required by the
:ref:Buffer protocol <bufferobjects>. The protocol defines how
an exporter object can expose its internal data to consumer objects.
.. c:member:: getbufferproc PyBufferProcs.bf_getbuffer
.. corresponding-type-slot:: Py_bf_getbuffer
The signature of this function is::
int (PyObject *exporter, Py_buffer *view, int flags);
Handle a request to exporter to fill in view as specified by flags. Except for point (3), an implementation of this function MUST take these steps:
(1) Check if the request can be met. If not, raise :exc:BufferError,
set :c:expr:view->obj to NULL and return -1.
(2) Fill in the requested fields.
(3) Increment an internal counter for the number of exports.
(4) Set :c:expr:view->obj to exporter and increment :c:expr:view->obj.
(5) Return 0.
Thread safety:
In the :term:free-threaded build, implementations must ensure:
The export counter increment in step (3) is atomic.
The underlying buffer data remains valid and at a stable memory location for the lifetime of all exports.
For objects that support resizing or reallocation (such as
:class:bytearray), the export counter is checked atomically before
such operations, and :exc:BufferError is raised if exports exist.
The function is safe to call concurrently from multiple threads.
See also :ref:thread-safety-memoryview for the Python-level
thread safety guarantees of :class:memoryview objects.
If exporter is part of a chain or tree of buffer providers, two main schemes can be used:
Re-export: Each member of the tree acts as the exporting object and
sets :c:expr:view->obj to a new reference to itself.
Redirect: The buffer request is redirected to the root object of the
tree. Here, :c:expr:view->obj will be a new reference to the root
object.
The individual fields of view are described in section
:ref:Buffer structure <buffer-structure>, the rules how an exporter
must react to specific requests are in section
:ref:Buffer request types <buffer-request-types>.
All memory pointed to in the :c:type:Py_buffer structure belongs to
the exporter and must remain valid until there are no consumers left.
:c:member:~Py_buffer.format, :c:member:~Py_buffer.shape,
:c:member:~Py_buffer.strides, :c:member:~Py_buffer.suboffsets
and :c:member:~Py_buffer.internal
are read-only for the consumer.
:c:func:PyBuffer_FillInfo provides an easy way of exposing a simple
bytes buffer while dealing correctly with all request types.
:c:func:PyObject_GetBuffer is the interface for the consumer that
wraps this function.
.. c:member:: releasebufferproc PyBufferProcs.bf_releasebuffer
.. corresponding-type-slot:: Py_bf_releasebuffer
The signature of this function is::
void (PyObject *exporter, Py_buffer *view);
Handle a request to release the resources of the buffer. If no resources
need to be released, :c:member:PyBufferProcs.bf_releasebuffer may be
NULL. Otherwise, a standard implementation of this function will take
these optional steps:
(1) Decrement an internal counter for the number of exports.
(2) If the counter is 0, free all memory associated with view.
Thread safety:
In the :term:free-threaded build:
The export counter decrement in step (1) must be atomic.
Resource cleanup when the counter reaches zero must be done atomically, as the final release may race with concurrent releases from other threads and dellocation must only happen once.
The exporter MUST use the :c:member:~Py_buffer.internal field to keep
track of buffer-specific resources. This field is guaranteed to remain
constant, while a consumer MAY pass a copy of the original buffer as the
view argument.
This function MUST NOT decrement :c:expr:view->obj, since that is
done automatically in :c:func:PyBuffer_Release (this scheme is
useful for breaking reference cycles).
:c:func:PyBuffer_Release is the interface for the consumer that
wraps this function.
.. _async-structs:
.. versionadded:: 3.5
.. c:type:: PyAsyncMethods
This structure holds pointers to the functions required to implement
:term:awaitable and :term:asynchronous iterator objects.
Here is the structure definition::
typedef struct {
unaryfunc am_await;
unaryfunc am_aiter;
unaryfunc am_anext;
sendfunc am_send;
} PyAsyncMethods;
.. c:member:: unaryfunc PyAsyncMethods.am_await
.. corresponding-type-slot:: Py_am_await
The signature of this function is::
PyObject *am_await(PyObject *self);
The returned object must be an :term:iterator, i.e. :c:func:PyIter_Check
must return 1 for it.
This slot may be set to NULL if an object is not an :term:awaitable.
.. c:member:: unaryfunc PyAsyncMethods.am_aiter
.. corresponding-type-slot:: Py_am_aiter
The signature of this function is::
PyObject *am_aiter(PyObject *self);
Must return an :term:asynchronous iterator object.
See :meth:~object.__anext__ for details.
This slot may be set to NULL if an object does not implement
asynchronous iteration protocol.
.. c:member:: unaryfunc PyAsyncMethods.am_anext
.. corresponding-type-slot:: Py_am_anext
The signature of this function is::
PyObject *am_anext(PyObject *self);
Must return an :term:awaitable object.
See :meth:~object.__anext__ for details.
This slot may be set to NULL.
.. c:member:: sendfunc PyAsyncMethods.am_send
.. corresponding-type-slot:: Py_am_send
The signature of this function is::
PySendResult am_send(PyObject *self, PyObject *arg, PyObject **result);
See :c:func:PyIter_Send for details.
This slot may be set to NULL.
.. versionadded:: 3.10
.. _slot-typedefs:
.. c:type:: PyObject *(*allocfunc)(PyTypeObject *cls, Py_ssize_t nitems)
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
:c:member:~PyObject.ob_refcnt set to 1 and :c:member:~PyObject.ob_type set to the type argument. If
the type's :c:member:~PyTypeObject.tp_itemsize is non-zero, the object's :c:member:~PyVarObject.ob_size field
should be initialized to nitems and the length of the allocated memory block
should be tp_basicsize + nitems*tp_itemsize, rounded up to a multiple of
sizeof(void*); otherwise, nitems is not used and the length of the block
should be :c:member:~PyTypeObject.tp_basicsize.
This function should not do any other instance initialization, not even to
allocate additional memory; that should be done by :c:member:~PyTypeObject.tp_new.
.. c:type:: void (*destructor)(PyObject *)
.. c:type:: void (*freefunc)(void *)
See :c:member:~PyTypeObject.tp_free.
.. c:type:: PyObject *(*newfunc)(PyTypeObject *, PyObject *, PyObject *)
See :c:member:~PyTypeObject.tp_new.
.. c:type:: int (*initproc)(PyObject *, PyObject *, PyObject *)
See :c:member:~PyTypeObject.tp_init.
.. c:type:: PyObject *(*reprfunc)(PyObject *)
See :c:member:~PyTypeObject.tp_repr.
.. c:type:: PyObject *(*getattrfunc)(PyObject *self, char *attr)
Return the value of the named attribute for the object.
.. c:type:: int (*setattrfunc)(PyObject *self, char *attr, PyObject *value)
Set the value of the named attribute for the object.
The value argument is set to NULL to delete the attribute.
.. c:type:: PyObject *(*getattrofunc)(PyObject *self, PyObject *attr)
Return the value of the named attribute for the object.
See :c:member:~PyTypeObject.tp_getattro.
.. c:type:: int (*setattrofunc)(PyObject *self, PyObject *attr, PyObject *value)
Set the value of the named attribute for the object.
The value argument is set to NULL to delete the attribute.
See :c:member:~PyTypeObject.tp_setattro.
.. c:type:: PyObject *(*descrgetfunc)(PyObject *, PyObject *, PyObject *)
See :c:member:~PyTypeObject.tp_descr_get.
.. c:type:: int (*descrsetfunc)(PyObject *, PyObject *, PyObject *)
See :c:member:~PyTypeObject.tp_descr_set.
.. c:type:: Py_hash_t (*hashfunc)(PyObject *)
See :c:member:~PyTypeObject.tp_hash.
.. c:type:: PyObject *(*richcmpfunc)(PyObject *, PyObject *, int)
See :c:member:~PyTypeObject.tp_richcompare.
.. c:type:: PyObject *(*getiterfunc)(PyObject *)
See :c:member:~PyTypeObject.tp_iter.
.. c:type:: PyObject *(*iternextfunc)(PyObject *)
See :c:member:~PyTypeObject.tp_iternext.
.. c:type:: Py_ssize_t (*lenfunc)(PyObject *)
.. c:type:: int (*getbufferproc)(PyObject *, Py_buffer *, int)
.. c:type:: void (*releasebufferproc)(PyObject *, Py_buffer *)
.. c:type:: PyObject *(*unaryfunc)(PyObject *)
.. c:type:: PyObject *(*binaryfunc)(PyObject *, PyObject *)
.. c:type:: PySendResult (*sendfunc)(PyObject *, PyObject *, PyObject **)
See :c:member:~PyAsyncMethods.am_send.
.. c:type:: PyObject *(*ternaryfunc)(PyObject *, PyObject *, PyObject *)
.. c:type:: PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t)
.. c:type:: int (*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *)
.. c:type:: int (*objobjproc)(PyObject *, PyObject *)
.. c:type:: int (*objobjargproc)(PyObject *, PyObject *, PyObject *)
.. _typedef-examples:
The following are simple examples of Python type definitions. They
include common usage you may encounter. Some demonstrate tricky corner
cases. For more examples, practical info, and a tutorial, see
:ref:defining-new-types and :ref:new-types-topics.
A basic :ref:static type <static-types>::
typedef struct { PyObject_HEAD const char *data; } MyObject;
static PyTypeObject MyObject_Type = { PyVarObject_HEAD_INIT(NULL, 0) .tp_name = "mymod.MyObject", .tp_basicsize = sizeof(MyObject), .tp_doc = PyDoc_STR("My objects"), .tp_new = myobj_new, .tp_dealloc = (destructor)myobj_dealloc, .tp_repr = (reprfunc)myobj_repr, };
You may also find older code (especially in the CPython code base) with a more verbose initializer::
static PyTypeObject MyObject_Type = { PyVarObject_HEAD_INIT(NULL, 0) "mymod.MyObject", /* tp_name / sizeof(MyObject), / tp_basicsize / 0, / tp_itemsize / (destructor)myobj_dealloc, / tp_dealloc / 0, / tp_vectorcall_offset / 0, / tp_getattr / 0, / tp_setattr / 0, / tp_as_async / (reprfunc)myobj_repr, / tp_repr / 0, / tp_as_number / 0, / tp_as_sequence / 0, / tp_as_mapping / 0, / tp_hash / 0, / tp_call / 0, / tp_str / 0, / tp_getattro / 0, / tp_setattro / 0, / tp_as_buffer / 0, / tp_flags / PyDoc_STR("My objects"), / tp_doc / 0, / tp_traverse / 0, / tp_clear / 0, / tp_richcompare / 0, / tp_weaklistoffset / 0, / tp_iter / 0, / tp_iternext / 0, / tp_methods / 0, / tp_members / 0, / tp_getset / 0, / tp_base / 0, / tp_dict / 0, / tp_descr_get / 0, / tp_descr_set / 0, / tp_dictoffset / 0, / tp_init / 0, / tp_alloc / myobj_new, / tp_new */ };
A type that supports weakrefs, instance dicts, and hashing::
typedef struct { PyObject_HEAD const char *data; } MyObject;
static PyTypeObject MyObject_Type = { PyVarObject_HEAD_INIT(NULL, 0) .tp_name = "mymod.MyObject", .tp_basicsize = sizeof(MyObject), .tp_doc = PyDoc_STR("My objects"), .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_MANAGED_DICT | Py_TPFLAGS_MANAGED_WEAKREF, .tp_new = myobj_new, .tp_traverse = (traverseproc)myobj_traverse, .tp_clear = (inquiry)myobj_clear, .tp_alloc = PyType_GenericNew, .tp_dealloc = (destructor)myobj_dealloc, .tp_repr = (reprfunc)myobj_repr, .tp_hash = (hashfunc)myobj_hash, .tp_richcompare = PyBaseObject_Type.tp_richcompare, };
A str subclass that cannot be subclassed and cannot be called
to create instances (e.g. uses a separate factory func) using
:c:macro:Py_TPFLAGS_DISALLOW_INSTANTIATION flag::
typedef struct { PyUnicodeObject raw; char *extra; } MyStr;
static PyTypeObject MyStr_Type = { PyVarObject_HEAD_INIT(NULL, 0) .tp_name = "mymod.MyStr", .tp_basicsize = sizeof(MyStr), .tp_base = NULL, // set to &PyUnicode_Type in module init .tp_doc = PyDoc_STR("my custom str"), .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION, .tp_repr = (reprfunc)myobj_repr, };
The simplest :ref:static type <static-types> with fixed-length instances::
typedef struct { PyObject_HEAD } MyObject;
static PyTypeObject MyObject_Type = { PyVarObject_HEAD_INIT(NULL, 0) .tp_name = "mymod.MyObject", };
The simplest :ref:static type <static-types> with variable-length instances::
typedef struct { PyObject_VAR_HEAD const char *data[1]; } MyObject;
static PyTypeObject MyObject_Type = { PyVarObject_HEAD_INIT(NULL, 0) .tp_name = "mymod.MyObject", .tp_basicsize = sizeof(MyObject) - sizeof(char *), .tp_itemsize = sizeof(char *), };