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Diffstat (limited to 'Doc/library/abc.rst')
| -rw-r--r-- | Doc/library/abc.rst | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/Doc/library/abc.rst b/Doc/library/abc.rst index 6f23596..1f21b57 100644 --- a/Doc/library/abc.rst +++ b/Doc/library/abc.rst @@ -12,9 +12,9 @@ -------------- This module provides the infrastructure for defining :term:`abstract base -classes <abstract base class>` (ABCs) in Python, as outlined in :pep:`3119`; see the PEP for why this -was added to Python. (See also :pep:`3141` and the :mod:`numbers` module -regarding a type hierarchy for numbers based on ABCs.) +classes <abstract base class>` (ABCs) in Python, as outlined in :pep:`3119`; +see the PEP for why this was added to Python. (See also :pep:`3141` and the +:mod:`numbers` module regarding a type hierarchy for numbers based on ABCs.) The :mod:`collections` module has some concrete classes that derive from ABCs; these can, of course, be further derived. In addition the @@ -23,7 +23,7 @@ a class or instance provides a particular interface, for example, is it hashable or a mapping. -This module provides the following class: +This module provides the following classes: .. class:: ABCMeta @@ -58,6 +58,10 @@ This module provides the following class: .. versionchanged:: 3.3 Returns the registered subclass, to allow usage as a class decorator. + .. versionchanged:: 3.4 + To detect calls to :meth:`register`, you can use the + :func:`get_cache_token` function. + You can also override this method in an abstract base class: .. method:: __subclasshook__(subclass) @@ -127,6 +131,19 @@ This module provides the following class: available as a method of ``Foo``, so it is provided separately. +.. class:: ABC + + A helper class that has :class:`ABCMeta` as its metaclass. With this class, + an abstract base class can be created by simply deriving from :class:`ABC`, + avoiding sometimes confusing metaclass usage. + + Note that the type of :class:`ABC` is still :class:`ABCMeta`, therefore + inheriting from :class:`ABC` requires the usual precautions regarding metaclass + usage, as multiple inheritance may lead to metaclass conflicts. + + .. versionadded:: 3.4 + + The :mod:`abc` module also provides the following decorators: .. decorator:: abstractmethod @@ -295,6 +312,19 @@ The :mod:`abc` module also provides the following decorators: :func:`abstractmethod`, making this decorator redundant. +The :mod:`abc` module also provides the following functions: + +.. function:: get_cache_token() + + Returns the current abstract base class cache token. + + The token is an opaque integer identifying the current version of the + abstract base class cache for virtual subclasses. This number changes + with every call to :meth:`ABCMeta.register` on any ABC. + + .. versionadded:: 3.4 + + .. rubric:: Footnotes .. [#] C++ programmers should note that Python's virtual base class |