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.

struct wrapperbase

   Describes a slot wrapper used by "PyDescr_NewWrapper()".

   Each "wrapperbase" record stores the Python-visible name and
   metadata for a special method implemented by a type slot, together
   with the wrapper function used to adapt that slot to Python's
   calling convention.

PyObject *PyDescr_NewWrapper(PyTypeObject *type, struct wrapperbase *base, void *wrapped)
    *Return value: New reference.*

   Create a new wrapper descriptor for extension type *type* from the
   "wrapperbase" structure *base* and the wrapped slot function
   pointer *wrapped*.

   Wrapper descriptors expose special methods implemented by type
   slots. This is the same kind of descriptor that CPython creates for
   slot-based special methods such as "__repr__" or "__add__", and it
   appears in Python as a "types.WrapperDescriptorType" object.

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

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 implemented via
   wrapper structures, and appear in Python as
   "types.WrapperDescriptorType" objects.

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_COMMON

   This is a *soft deprecated* 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").


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.
