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Diffstat (limited to 'Doc/c-api/object.rst')
| -rw-r--r-- | Doc/c-api/object.rst | 63 |
1 files changed, 34 insertions, 29 deletions
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst index 7c2f6d5..187ac01 100644 --- a/Doc/c-api/object.rst +++ b/Doc/c-api/object.rst @@ -187,40 +187,45 @@ Object Protocol a TypeError is raised when *o* is an integer instead of a zero-initialized bytes object. + +.. c:function:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls) + + Return ``1`` if the class *derived* is identical to or derived from the class + *cls*, otherwise return ``0``. In case of an error, return ``-1``. + + If *cls* is a tuple, the check will be done against every entry in *cls*. + The result will be ``1`` when at least one of the checks returns ``1``, + otherwise it will be ``0``. + + If *cls* has a :meth:`~class.__subclasscheck__` method, it will be called to + determine the subclass status as described in :pep:`3119`. Otherwise, + *derived* is a subclass of *cls* if it is a direct or indirect subclass, + i.e. contained in ``cls.__mro__``. + + Normally only class objects, i.e. instances of :class:`type` or a derived + class, are considered classes. However, objects can override this by haivng + a :attr:`__bases__` attribute (which must be a tuple of base classes). + + .. c:function:: int PyObject_IsInstance(PyObject *inst, PyObject *cls) - Returns ``1`` if *inst* is an instance of the class *cls* or a subclass of - *cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception. If - *cls* is a type object rather than a class object, :c:func:`PyObject_IsInstance` - returns ``1`` if *inst* is of type *cls*. If *cls* is a tuple, the check will - be done against every entry in *cls*. The result will be ``1`` when at least one - of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a - class instance and *cls* is neither a type object, nor a class object, nor a - tuple, *inst* must have a :attr:`~instance.__class__` attribute --- the - class relationship of the value of that attribute with *cls* will be used - to determine the result of this function. - - -Subclass determination is done in a fairly straightforward way, but includes a -wrinkle that implementors of extensions to the class system may want to be aware -of. If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of -:class:`A` if it inherits from :class:`A` either directly or indirectly. If -either is not a class object, a more general mechanism is used to determine the -class relationship of the two objects. When testing if *B* is a subclass of -*A*, if *A* is *B*, :c:func:`PyObject_IsSubclass` returns true. If *A* and *B* -are different objects, *B*'s :attr:`~class.__bases__` attribute is searched in -a depth-first fashion for *A* --- the presence of the :attr:`~class.__bases__` -attribute is considered sufficient for this determination. + Return ``1`` if *inst* is an instance of the class *cls* or a subclass of + *cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception. + If *cls* is a tuple, the check will be done against every entry in *cls*. + The result will be ``1`` when at least one of the checks returns ``1``, + otherwise it will be ``0``. -.. c:function:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls) + If *cls* has a :meth:`~class.__instancecheck__` method, it will be called to + determine the subclass status as described in :pep:`3119`. Otherwise, *inst* + is an instance of *cls* if its class is a subclass of *cls*. + + An instance *inst* can override what is considered its class by having a + :attr:`__class__` attribute. - Returns ``1`` if the class *derived* is identical to or derived from the class - *cls*, otherwise returns ``0``. In case of an error, returns ``-1``. If *cls* - is a tuple, the check will be done against every entry in *cls*. The result will - be ``1`` when at least one of the checks returns ``1``, otherwise it will be - ``0``. If either *derived* or *cls* is not an actual class object (or tuple), - this function uses the generic algorithm described above. + An object *cls* can override if it is considered a class, and what its base + classes are, by having a :attr:`__bases__` attribute (which must be a tuple + of base classes). .. c:function:: int PyCallable_Check(PyObject *o) |