mirror of https://github.com/python/cpython
#6928: fix class docs w.r.t. new metaclasses.
This commit is contained in:
parent
502c3eb52f
commit
65e5f80c48
|
@ -552,24 +552,27 @@ Class definitions
|
|||
|
||||
A class definition defines a class object (see section :ref:`types`):
|
||||
|
||||
.. XXX need to document PEP 3115 changes here (new metaclasses)
|
||||
|
||||
.. productionlist::
|
||||
classdef: [`decorators`] "class" `classname` [`inheritance`] ":" `suite`
|
||||
inheritance: "(" [`expression_list`] ")"
|
||||
inheritance: "(" [`argument_list` [","] ] ")"
|
||||
classname: `identifier`
|
||||
|
||||
|
||||
A class definition is an executable statement. It first evaluates the
|
||||
inheritance list, if present. Each item in the inheritance list should evaluate
|
||||
to a class object or class type which allows subclassing. The class's suite is
|
||||
then executed in a new execution frame (see section :ref:`naming`), using a
|
||||
newly created local namespace and the original global namespace. (Usually, the
|
||||
suite contains only function definitions.) When the class's suite finishes
|
||||
execution, its execution frame is discarded but its local namespace is
|
||||
saved. [#]_ A class object is then created using the inheritance list for the
|
||||
base classes and the saved local namespace for the attribute dictionary. The
|
||||
class name is bound to this class object in the original local namespace.
|
||||
A class definition is an executable statement. The inheritance list usually
|
||||
gives a list of base classes (see :ref:`metaclasses` for more advanced uses), so
|
||||
each item in the list should evaluate to a class object which allows
|
||||
subclassing.
|
||||
|
||||
The class's suite is then executed in a new execution frame (see :ref:`naming`),
|
||||
using a newly created local namespace and the original global namespace.
|
||||
(Usually, the suite contains mostly function definitions.) When the class's
|
||||
suite finishes execution, its execution frame is discarded but its local
|
||||
namespace is saved. [#]_ A class object is then created using the inheritance
|
||||
list for the base classes and the saved local namespace for the attribute
|
||||
dictionary. The class name is bound to this class object in the original local
|
||||
namespace.
|
||||
|
||||
Class creation can be customized heavily using :ref:`metaclasses <metaclasses>`.
|
||||
|
||||
Classes can also be decorated; as with functions, ::
|
||||
|
||||
|
@ -583,25 +586,20 @@ is equivalent to ::
|
|||
Foo = f1(arg)(f2(Foo))
|
||||
|
||||
**Programmer's note:** Variables defined in the class definition are class
|
||||
variables; they are shared by instances. Instance variables can be set in a
|
||||
method with ``self.name = value``. Both class and instance variables are
|
||||
accessible through the notation "``self.name``", and an instance variable hides
|
||||
a class variable with the same name when accessed in this way. Class variables
|
||||
can be used as defaults for instance variables, but using mutable values there
|
||||
can lead to unexpected results. Descriptors can be used to create instance
|
||||
variables with different implementation details.
|
||||
attributes; they are shared by instances. Instance attributes can be set in a
|
||||
method with ``self.name = value``. Both class and instance attributes are
|
||||
accessible through the notation "``self.name``", and an instance attribute hides
|
||||
a class attribute with the same name when accessed in this way. Class
|
||||
attributes can be used as defaults for instance attributes, but using mutable
|
||||
values there can lead to unexpected results. :ref:`Descriptors <descriptors>`
|
||||
can be used to create instance variables with different implementation details.
|
||||
|
||||
.. XXX add link to descriptor docs above
|
||||
|
||||
.. seealso::
|
||||
|
||||
:pep:`3116` - Metaclasses in Python 3
|
||||
:pep:`3129` - Class Decorators
|
||||
|
||||
Class definitions, like function definitions, may be wrapped by one or more
|
||||
:term:`decorator` expressions. The evaluation rules for the decorator
|
||||
expressions are the same as for functions. The result must be a class object,
|
||||
which is then bound to the class name.
|
||||
|
||||
|
||||
.. rubric:: Footnotes
|
||||
|
||||
|
|
Loading…
Reference in New Issue