[Python-checkins] r83805 - python/branches/release31-maint/Doc/library/collections.rst
raymond.hettinger
python-checkins at python.org
Sun Aug 8 02:32:32 CEST 2010
Author: raymond.hettinger
Date: Sun Aug 8 02:32:32 2010
New Revision: 83805
Log:
Backport doc readability improvements for the collections module.
Modified:
python/branches/release31-maint/Doc/library/collections.rst
Modified: python/branches/release31-maint/Doc/library/collections.rst
==============================================================================
--- python/branches/release31-maint/Doc/library/collections.rst (original)
+++ python/branches/release31-maint/Doc/library/collections.rst Sun Aug 8 02:32:32 2010
@@ -12,131 +12,24 @@
import itertools
__name__ = '<doctest>'
-This module implements high-performance container datatypes. Currently,
-there are four datatypes, :class:`Counter`, :class:`deque`, :class:`OrderedDict` and
-:class:`defaultdict`, and one datatype factory function, :func:`namedtuple`.
-
-The specialized containers provided in this module provide alternatives
-to Python's general purpose built-in containers, :class:`dict`,
-:class:`list`, :class:`set`, and :class:`tuple`.
-
-In addition to containers, the collections module provides some ABCs
-(abstract base classes) that can be used to test whether a class
-provides a particular interface, for example, whether it is hashable or
-a mapping.
-
-ABCs - abstract base classes
-----------------------------
-
-The collections module offers the following ABCs:
-
-========================= ===================== ====================== ====================================================
-ABC Inherits Abstract Methods Mixin Methods
-========================= ===================== ====================== ====================================================
-:class:`Container` ``__contains__``
-:class:`Hashable` ``__hash__``
-:class:`Iterable` ``__iter__``
-:class:`Iterator` :class:`Iterable` ``__next__`` ``__iter__``
-:class:`Sized` ``__len__``
-:class:`Callable` ``__call__``
-
-:class:`Sequence` :class:`Sized`, ``__getitem__`` ``__contains__``. ``__iter__``, ``__reversed__``.
- :class:`Iterable`, ``index``, and ``count``
- :class:`Container`
-
-:class:`MutableSequence` :class:`Sequence` ``__setitem__`` Inherited Sequence methods and
- ``__delitem__``, ``append``, ``reverse``, ``extend``, ``pop``,
- and ``insert`` ``remove``, and ``__iadd__``
-
-:class:`Set` :class:`Sized`, ``__le__``, ``__lt__``, ``__eq__``, ``__ne__``,
- :class:`Iterable`, ``__gt__``, ``__ge__``, ``__and__``, ``__or__``
- :class:`Container` ``__sub__``, ``__xor__``, and ``isdisjoint``
-
-:class:`MutableSet` :class:`Set` ``add`` and Inherited Set methods and
- ``discard`` ``clear``, ``pop``, ``remove``, ``__ior__``,
- ``__iand__``, ``__ixor__``, and ``__isub__``
-
-:class:`Mapping` :class:`Sized`, ``__getitem__`` ``__contains__``, ``keys``, ``items``, ``values``,
- :class:`Iterable`, ``get``, ``__eq__``, and ``__ne__``
- :class:`Container`
-
-:class:`MutableMapping` :class:`Mapping` ``__setitem__`` and Inherited Mapping methods and
- ``__delitem__`` ``pop``, ``popitem``, ``clear``, ``update``,
- and ``setdefault``
-
-
-:class:`MappingView` :class:`Sized` ``__len__``
-:class:`KeysView` :class:`MappingView`, ``__contains__``,
- :class:`Set` ``__iter__``
-:class:`ItemsView` :class:`MappingView`, ``__contains__``,
- :class:`Set` ``__iter__``
-:class:`ValuesView` :class:`MappingView` ``__contains__``, ``__iter__``
-========================= ===================== ====================== ====================================================
-
-These ABCs allow us to ask classes or instances if they provide
-particular functionality, for example::
-
- size = None
- if isinstance(myvar, collections.Sized):
- size = len(myvar)
-
-Several of the ABCs are also useful as mixins that make it easier to develop
-classes supporting container APIs. For example, to write a class supporting
-the full :class:`Set` API, it only necessary to supply the three underlying
-abstract methods: :meth:`__contains__`, :meth:`__iter__`, and :meth:`__len__`.
-The ABC supplies the remaining methods such as :meth:`__and__` and
-:meth:`isdisjoint` ::
-
- class ListBasedSet(collections.Set):
- ''' Alternate set implementation favoring space over speed
- and not requiring the set elements to be hashable. '''
- def __init__(self, iterable):
- self.elements = lst = []
- for value in iterable:
- if value not in lst:
- lst.append(value)
- def __iter__(self):
- return iter(self.elements)
- def __contains__(self, value):
- return value in self.elements
- def __len__(self):
- return len(self.elements)
-
- s1 = ListBasedSet('abcdef')
- s2 = ListBasedSet('defghi')
- overlap = s1 & s2 # The __and__() method is supported automatically
-
-Notes on using :class:`Set` and :class:`MutableSet` as a mixin:
-
-(1)
- Since some set operations create new sets, the default mixin methods need
- a way to create new instances from an iterable. The class constructor is
- assumed to have a signature in the form ``ClassName(iterable)``.
- That assumption is factored-out to an internal classmethod called
- :meth:`_from_iterable` which calls ``cls(iterable)`` to produce a new set.
- If the :class:`Set` mixin is being used in a class with a different
- constructor signature, you will need to override :meth:`from_iterable`
- with a classmethod that can construct new instances from
- an iterable argument.
-
-(2)
- To override the comparisons (presumably for speed, as the
- semantics are fixed), redefine :meth:`__le__` and
- then the other operations will automatically follow suit.
-
-(3)
- The :class:`Set` mixin provides a :meth:`_hash` method to compute a hash value
- for the set; however, :meth:`__hash__` is not defined because not all sets
- are hashable or immutable. To add set hashabilty using mixins,
- inherit from both :meth:`Set` and :meth:`Hashable`, then define
- ``__hash__ = Set._hash``.
-
-.. seealso::
-
- * `OrderedSet recipe <http://code.activestate.com/recipes/576694/>`_ for an
- example built on :class:`MutableSet`.
-
- * For more about ABCs, see the :mod:`abc` module and :pep:`3119`.
+This module implements specialized container datatypes providing alternatives to
+Python's general purpose built-in containers, :class:`dict`, :class:`list`,
+:class:`set`, and :class:`tuple`.
+
+===================== ====================================================================
+:func:`namedtuple` factory function for creating tuple subclasses with named fields
+:class:`deque` list-like container with fast appends and pops on either end
+:class:`Counter` dict subclass for counting hashable objects
+:class:`OrderedDict` dict subclass that remembers the order entries were added
+:class:`defaultdict` dict subclass that calls a factory function to supply missing values
+:class:`UserDict` wrapper around dictionary objects for easier dict subclassing
+:class:`UserList` wrapper around list objects for easier list subclassing
+:class:`UserString` wrapper around string objects for easier string subclassing
+===================== ====================================================================
+
+In addition to the concrete container classes, the collections module provides
+ABCs (abstract base classes) that can be used to test whether a class provides a
+particular interface, for example, whether it is hashable or a mapping.
:class:`Counter` objects
@@ -1009,3 +902,117 @@
be an instance of :class:`bytes`, :class:`str`, :class:`UserString` (or a
subclass) or an arbitrary sequence which can be converted into a string using
the built-in :func:`str` function.
+
+
+ABCs - abstract base classes
+----------------------------
+
+The collections module offers the following ABCs:
+
+========================= ===================== ====================== ====================================================
+ABC Inherits Abstract Methods Mixin Methods
+========================= ===================== ====================== ====================================================
+:class:`Container` ``__contains__``
+:class:`Hashable` ``__hash__``
+:class:`Iterable` ``__iter__``
+:class:`Iterator` :class:`Iterable` ``__next__`` ``__iter__``
+:class:`Sized` ``__len__``
+:class:`Callable` ``__call__``
+
+:class:`Sequence` :class:`Sized`, ``__getitem__`` ``__contains__``. ``__iter__``, ``__reversed__``.
+ :class:`Iterable`, ``index``, and ``count``
+ :class:`Container`
+
+:class:`MutableSequence` :class:`Sequence` ``__setitem__`` Inherited Sequence methods and
+ ``__delitem__``, ``append``, ``reverse``, ``extend``, ``pop``,
+ and ``insert`` ``remove``, and ``__iadd__``
+
+:class:`Set` :class:`Sized`, ``__le__``, ``__lt__``, ``__eq__``, ``__ne__``,
+ :class:`Iterable`, ``__gt__``, ``__ge__``, ``__and__``, ``__or__``
+ :class:`Container` ``__sub__``, ``__xor__``, and ``isdisjoint``
+
+:class:`MutableSet` :class:`Set` ``add`` and Inherited Set methods and
+ ``discard`` ``clear``, ``pop``, ``remove``, ``__ior__``,
+ ``__iand__``, ``__ixor__``, and ``__isub__``
+
+:class:`Mapping` :class:`Sized`, ``__getitem__`` ``__contains__``, ``keys``, ``items``, ``values``,
+ :class:`Iterable`, ``get``, ``__eq__``, and ``__ne__``
+ :class:`Container`
+
+:class:`MutableMapping` :class:`Mapping` ``__setitem__`` and Inherited Mapping methods and
+ ``__delitem__`` ``pop``, ``popitem``, ``clear``, ``update``,
+ and ``setdefault``
+
+
+:class:`MappingView` :class:`Sized` ``__len__``
+:class:`KeysView` :class:`MappingView`, ``__contains__``,
+ :class:`Set` ``__iter__``
+:class:`ItemsView` :class:`MappingView`, ``__contains__``,
+ :class:`Set` ``__iter__``
+:class:`ValuesView` :class:`MappingView` ``__contains__``, ``__iter__``
+========================= ===================== ====================== ====================================================
+
+These ABCs allow us to ask classes or instances if they provide
+particular functionality, for example::
+
+ size = None
+ if isinstance(myvar, collections.Sized):
+ size = len(myvar)
+
+Several of the ABCs are also useful as mixins that make it easier to develop
+classes supporting container APIs. For example, to write a class supporting
+the full :class:`Set` API, it only necessary to supply the three underlying
+abstract methods: :meth:`__contains__`, :meth:`__iter__`, and :meth:`__len__`.
+The ABC supplies the remaining methods such as :meth:`__and__` and
+:meth:`isdisjoint` ::
+
+ class ListBasedSet(collections.Set):
+ ''' Alternate set implementation favoring space over speed
+ and not requiring the set elements to be hashable. '''
+ def __init__(self, iterable):
+ self.elements = lst = []
+ for value in iterable:
+ if value not in lst:
+ lst.append(value)
+ def __iter__(self):
+ return iter(self.elements)
+ def __contains__(self, value):
+ return value in self.elements
+ def __len__(self):
+ return len(self.elements)
+
+ s1 = ListBasedSet('abcdef')
+ s2 = ListBasedSet('defghi')
+ overlap = s1 & s2 # The __and__() method is supported automatically
+
+Notes on using :class:`Set` and :class:`MutableSet` as a mixin:
+
+(1)
+ Since some set operations create new sets, the default mixin methods need
+ a way to create new instances from an iterable. The class constructor is
+ assumed to have a signature in the form ``ClassName(iterable)``.
+ That assumption is factored-out to an internal classmethod called
+ :meth:`_from_iterable` which calls ``cls(iterable)`` to produce a new set.
+ If the :class:`Set` mixin is being used in a class with a different
+ constructor signature, you will need to override :meth:`from_iterable`
+ with a classmethod that can construct new instances from
+ an iterable argument.
+
+(2)
+ To override the comparisons (presumably for speed, as the
+ semantics are fixed), redefine :meth:`__le__` and
+ then the other operations will automatically follow suit.
+
+(3)
+ The :class:`Set` mixin provides a :meth:`_hash` method to compute a hash value
+ for the set; however, :meth:`__hash__` is not defined because not all sets
+ are hashable or immutable. To add set hashabilty using mixins,
+ inherit from both :meth:`Set` and :meth:`Hashable`, then define
+ ``__hash__ = Set._hash``.
+
+.. seealso::
+
+ * `OrderedSet recipe <http://code.activestate.com/recipes/576694/>`_ for an
+ example built on :class:`MutableSet`.
+
+ * For more about ABCs, see the :mod:`abc` module and :pep:`3119`.
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