.. index:: pair: object; method
Methods are functions that are called using the attribute notation. There are
-two flavors: built-in methods (such as :meth:`append` on lists) and class
-instance methods. Built-in methods are described with the types that support
-them.
+two flavors: :ref:`built-in methods <builtin-methods>` (such as :meth:`append`
+on lists) and :ref:`class instance method <instance-methods>`.
+Built-in methods are described with the types that support them.
If you access a method (a function defined in a class namespace) through an
instance, you get a special object: a :dfn:`bound method` (also called
-:dfn:`instance method`) object. When called, it will add the ``self`` argument
+:ref:`instance method <instance-methods>`) object. When called, it will add
+the ``self`` argument
to the argument list. Bound methods have two special read-only attributes:
-``m.__self__`` is the object on which the method operates, and ``m.__func__`` is
+:attr:`m.__self__ <method.__self__>` is the object on which the method
+operates, and :attr:`m.__func__ <method.__func__>` is
the function implementing the method. Calling ``m(arg-1, arg-2, ..., arg-n)``
is completely equivalent to calling ``m.__func__(m.__self__, arg-1, arg-2, ...,
arg-n)``.
-Like function objects, bound method objects support getting arbitrary
+Like :ref:`function objects <user-defined-funcs>`, bound method objects support
+getting arbitrary
attributes. However, since method attributes are actually stored on the
-underlying function object (``meth.__func__``), setting method attributes on
+underlying function object (:attr:`method.__func__`), setting method attributes on
bound methods is disallowed. Attempting to set an attribute on a method
results in an :exc:`AttributeError` being raised. In order to set a method
-attribute, you need to explicitly set it on the underlying function object::
+attribute, you need to explicitly set it on the underlying function object:
+
+.. doctest::
>>> class C:
... def method(self):
>>> c.method.whoami
'my name is method'
-See :ref:`types` for more information.
+See :ref:`instance-methods` for more information.
.. index:: object; code, code object
:ref:`calls`) can be applied:
+.. _user-defined-funcs:
+
User-defined functions
^^^^^^^^^^^^^^^^^^^^^^
single: __name__ (method attribute)
single: __module__ (method attribute)
-Special read-only attributes: :attr:`__self__` is the class instance object,
-:attr:`__func__` is the function object; :attr:`__doc__` is the method's
-documentation (same as ``__func__.__doc__``); :attr:`~definition.__name__` is the
-method name (same as ``__func__.__name__``); :attr:`__module__` is the
-name of the module the method was defined in, or ``None`` if unavailable.
+Special read-only attributes:
+
+.. list-table::
+
+ * - .. attribute:: method.__self__
+ - Refers to the class instance object to which the method is
+ :ref:`bound <method-binding>`
+
+ * - .. attribute:: method.__func__
+ - Refers to the original function object
+
+ * - .. attribute:: method.__doc__
+ - The method's documentation (same as :attr:`!method.__func__.__doc__`).
+ A :class:`string <str>` if the original function had a docstring, else
+ ``None``.
+
+ * - .. attribute:: method.__name__
+ - The name of the method (same as :attr:`!method.__func__.__name__`)
+
+ * - .. attribute:: method.__module__
+ - The name of the module the method was defined in, or ``None`` if
+ unavailable.
Methods also support accessing (but not setting) the arbitrary function
-attributes on the underlying function object.
+attributes on the underlying :ref:`function object <user-defined-funcs>`.
User-defined method objects may be created when getting an attribute of a
class (perhaps via an instance of that class), if that attribute is a
-user-defined function object or a class method object.
+user-defined :ref:`function object <user-defined-funcs>` or a
+:class:`classmethod` object.
+
+.. _method-binding:
When an instance method object is created by retrieving a user-defined
-function object from a class via one of its instances, its
-:attr:`__self__` attribute is the instance, and the method object is said
-to be bound. The new method's :attr:`__func__` attribute is the original
-function object.
-
-When an instance method object is created by retrieving a class method
-object from a class or instance, its :attr:`__self__` attribute is the
-class itself, and its :attr:`__func__` attribute is the function object
+:ref:`function object <user-defined-funcs>` from a class via one of its
+instances, its :attr:`~method.__self__` attribute is the instance, and the
+method object is said to be *bound*. The new method's :attr:`~method.__func__`
+attribute is the original function object.
+
+When an instance method object is created by retrieving a :class:`classmethod`
+object from a class or instance, its :attr:`~method.__self__` attribute is the
+class itself, and its :attr:`~method.__func__` attribute is the function object
underlying the class method.
When an instance method object is called, the underlying function
-(:attr:`__func__`) is called, inserting the class instance
-(:attr:`__self__`) in front of the argument list. For instance, when
+(:attr:`~method.__func__`) is called, inserting the class instance
+(:attr:`~method.__self__`) in front of the argument list. For instance, when
:class:`!C` is a class which contains a definition for a function
:meth:`!f`, and ``x`` is an instance of :class:`!C`, calling ``x.f(1)`` is
equivalent to calling ``C.f(x, 1)``.
-When an instance method object is derived from a class method object, the
-"class instance" stored in :attr:`__self__` will actually be the class
+When an instance method object is derived from a :class:`classmethod` object, the
+"class instance" stored in :attr:`~method.__self__` will actually be the class
itself, so that calling either ``x.f(1)`` or ``C.f(1)`` is equivalent to
calling ``f(C,1)`` where ``f`` is the underlying function.
-Note that the transformation from function object to instance method
+Note that the transformation from :ref:`function object <user-defined-funcs>`
+to instance method
object happens each time the attribute is retrieved from the instance. In
some cases, a fruitful optimization is to assign the attribute to a local
variable and call that local variable. Also notice that this
the module the function was defined in or ``None`` if unavailable.
+.. _builtin-methods:
+
Built-in methods
^^^^^^^^^^^^^^^^
This is really a different disguise of a built-in function, this time containing
an object passed to the C function as an implicit extra argument. An example of
a built-in method is ``alist.append()``, assuming *alist* is a list object. In
-this case, the special read-only attribute :attr:`__self__` is set to the object
-denoted by *alist*.
+this case, the special read-only attribute :attr:`!__self__` is set to the object
+denoted by *alist*. (The attribute has the same semantics as it does with
+:attr:`other instance methods <method.__self__>`.)
Classes
When a class attribute reference (for class :class:`!C`, say) would yield a
class method object, it is transformed into an instance method object whose
-:attr:`__self__` attribute is :class:`!C`. When it would yield a static
-method object, it is transformed into the object wrapped by the static method
+:attr:`~method.__self__` attribute is :class:`!C`.
+When it would yield a :class:`staticmethod` object,
+it is transformed into the object wrapped by the static method
object. See section :ref:`descriptors` for another way in which attributes
retrieved from a class may differ from those actually contained in its
:attr:`~object.__dict__`.
there, and the instance's class has an attribute by that name, the search
continues with the class attributes. If a class attribute is found that is a
user-defined function object, it is transformed into an instance method
-object whose :attr:`__self__` attribute is the instance. Static method and
+object whose :attr:`~method.__self__` attribute is the instance. Static method and
class method objects are also transformed; see above under "Classes". See
section :ref:`descriptors` for another way in which attributes of a class
retrieved via its instances may differ from the objects actually stored in