Descriptor Objects

“Descriptors” are objects that describe some attribute of an object. They are found in the dictionary of type objects.

PyObject *PyDescr_NewGetSet(PyTypeObject *type, struct PyGetSetDef *getset)

Return value: New reference. Part of the Stable ABI.

Create a new get-set descriptor for extension type type from the PyGetSetDef structure getset.

Get-set descriptors expose attributes implemented by C getter and setter functions rather than stored directly in the instance. This is the same kind of descriptor created for entries in tp_getset, and it appears in Python as a types.GetSetDescriptorType object.

On success, return a strong reference to the descriptor. Return NULL with an exception set on failure.

PyObject *PyDescr_NewMember(PyTypeObject *type, struct PyMemberDef *member)

Return value: New reference. Part of the Stable ABI.

Create a new member descriptor for extension type type from the PyMemberDef structure member.

Member descriptors expose fields in the type’s C struct as Python attributes. This is the same kind of descriptor created for entries in tp_members, and it appears in Python as a types.MemberDescriptorType object.

On success, return a strong reference to the descriptor. Return NULL with an exception set on failure.

PyTypeObject PyMemberDescr_Type

Part of the Stable ABI.

The type object for member descriptor objects created from PyMemberDef structures. These descriptors expose fields of a C struct as attributes on a type, and correspond to types.MemberDescriptorType objects in Python.

PyTypeObject PyGetSetDescr_Type

Part of the Stable ABI.

The type object for get/set descriptor objects created from PyGetSetDef structures. These descriptors implement attributes whose value is computed by C getter and setter functions, and are used for many built-in type attributes. They correspond to types.GetSetDescriptorType objects in Python.

PyObject *PyDescr_NewMethod(PyTypeObject *type, struct PyMethodDef *meth)

Return value: New reference. Part of the Stable ABI.

Create a new method descriptor for extension type type from the PyMethodDef structure meth.

Method descriptors expose C functions as methods on a type. This is the same kind of descriptor created for entries in tp_methods, and it appears in Python as a types.MethodDescriptorType object.

On success, return a strong reference to the descriptor. Return NULL with an exception set on failure.

PyTypeObject PyMethodDescr_Type

Part of the Stable ABI.

The type object for method descriptor objects created from PyMethodDef structures. These descriptors expose C functions as methods on a type, and correspond to types.MethodDescriptorType objects in Python.

PyTypeObject PyWrapperDescr_Type

Part of the Stable ABI.

The type object for wrapper descriptor objects created by PyDescr_NewWrapper() and PyWrapper_New().

Wrapper descriptors are used internally to expose special methods such as __repr__ or __add__, which are implemented by type slots. The type is exposed in Python as types.WrapperDescriptorType.

PyObject *PyDescr_NewWrapper(PyTypeObject *type, struct wrapperbase *base, void *wrapped)

Return value: New reference.

Create a new wrapper descriptor of type PyWrapperDescr_Type.

This function is meant for internal use only; it and related API (struct wrapperbase and the PyWrapperFlag_KEYWORDS flag) are exposed publicly for backwards compatibility reasons.

See PyCMethod_New() for wrapping a C function.

PyObject *PyDescr_NewClassMethod(PyTypeObject *type, PyMethodDef *method)

Return value: New reference. Part of the Stable ABI.

Create a new class method descriptor for extension type type from the PyMethodDef structure method.

Class method descriptors expose C methods that receive the class rather than an instance when accessed. This is the same kind of descriptor created for METH_CLASS entries in tp_methods, and it appears in Python as a types.ClassMethodDescriptorType object.

On success, return a strong reference to the descriptor. Return NULL with an exception set on failure.

int PyDescr_IsData(PyObject *descr)

Return non-zero if the descriptor object descr describes a data attribute, or 0 if it describes a method. descr must be a descriptor object; there is no error checking.

PyObject *PyWrapper_New(PyObject *d, PyObject *self)

Return value: New reference. Part of the Stable ABI.

Create a new bound wrapper object from the wrapper descriptor d and the instance self.

This is the bound form of a wrapper descriptor created by PyDescr_NewWrapper(). CPython creates these objects when a slot wrapper is accessed through an instance, and they appear in Python as types.MethodWrapperType objects.

On success, return a strong reference to the wrapper object. Return NULL with an exception set on failure.

PyDescr_TYPE(descr)

Return a borrowed reference to the type that the descriptor descr belongs to. This is accessible as __objclass__ in Python.

descr must be a descriptor object created by one of the PyDescr_New* functions (an instance of PyMethodDescr_Type, PyClassMethodDescr_Type, PyMemberDescr_Type, PyGetSetDescr_Type, or PyWrapperDescr_Type). If the passed descriptor is not an instance of one of these types, the behavior is undefined.

PyDescr_NAME(descr)

Return the name of the descriptor descr as a borrowed reference to a str object. This is available as __name__ in Python.

descr must be a descriptor object created by one of the PyDescr_New* functions. If not, the behavior is undefined.

PyDescr_COMMON

This is a macro including the common fields for a descriptor object.

This was included in Python’s C API by mistake; do not use it in extensions. For creating custom descriptor objects, create a class implementing the descriptor protocol (tp_descr_get and tp_descr_set).

Soft deprecated since version 3.15.

Built-in descriptors

PyTypeObject PyProperty_Type

Part of the Stable ABI.

The type object for property objects. This is the same object as property in the Python layer.

PyTypeObject PySuper_Type

Part of the Stable ABI.

The type object for super objects. This is the same object as super in the Python layer.

PyTypeObject PyClassMethod_Type

The type of class method objects. This is the same object as classmethod in the Python layer.

PyTypeObject PyClassMethodDescr_Type

Part of the Stable ABI.

The type object for C-level class method descriptor objects. This is the type of the descriptors created for classmethod() defined in C extension types, and corresponds to types.ClassMethodDescriptorType objects in Python.

PyObject *PyClassMethod_New(PyObject *callable)

Create a new classmethod object wrapping callable. callable must be a callable object and must not be NULL.

On success, this function returns a strong reference to a new class method descriptor. On failure, this function returns NULL with an exception set.

PyTypeObject PyStaticMethod_Type

The type of static method objects. This is the same object as staticmethod in the Python layer.

PyObject *PyStaticMethod_New(PyObject *callable)

Create a new staticmethod object wrapping callable. callable must be a callable object and must not be NULL.

On success, this function returns a strong reference to a new static method descriptor. On failure, this function returns NULL with an exception set.