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Minor doc tweaks.

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Raymond Hettinger 2009-01-14 00:15:21 +00:00
parent 717c083e8d
commit 59894127e4
1 changed files with 17 additions and 19 deletions
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Doc/library/collections.rst
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@ -188,26 +188,24 @@ For example::
>>> c = Counter() # a new, empty counter >>> c = Counter() # a new, empty counter
>>> c = Counter('gallahad') # a new counter from an iterable >>> c = Counter('gallahad') # a new counter from an iterable
>>> c = Counter({'a': 4, 'b': 2}) # a new counter from a mapping >>> c = Counter({'red': 4, 'blue': 2}) # a new counter from a mapping
The returned object has a dictionary style interface except that it returns The returned object has a dictionary style interface except that it returns
a zero count for missing items (instead of raising a :exc:`KeyError` like a a zero count for missing items (instead of raising a :exc:`KeyError` like a
dictionary would):: dictionary would)::
>>> c = Counter(['if', 'your', 'peril', 'be']) >>> c = Counter(['egg', 'ham'])
>>> c['questions'] # count of a missing element is zero >>> c['bacon'] # count of a missing element is zero
0 0
Assigning a count of zero or reducing the count to zero leaves the Assigning a count of zero or reducing the count to zero leaves the
element in the dictionary. Use ``del`` to remove the entry entirely: element in the dictionary. Use ``del`` to remove the entry entirely:
>>> c = Counter(['arthur', 'gwain']) >>> c = Counter(['arthur', 'gwain'])
>>> c['arthur'] = 0 # set the count of "arthur" to zero >>> c['arthur'] = 0 # set the count of 'arthur' to zero
>>> 'arthur' in c # but "arthur" is still in the counter >>> 'arthur' in c # but 'arthur' is still in the counter
True True
>>> del c['arthur'] # del will completely remove the entry >>> del c['arthur'] # del will completely remove the entry
>>> 'arthur' in c
False
.. versionadded:: 2.7 .. versionadded:: 2.7
@ -267,27 +265,27 @@ Common patterns for working with :class:`Counter` objects::
dict(c) # convert to a regular dictionary dict(c) # convert to a regular dictionary
c.items() # convert to a list of (elem, cnt) pairs c.items() # convert to a list of (elem, cnt) pairs
Counter(dict(list_of_pairs)) # convert from a list of (elem, cnt) pairs Counter(dict(list_of_pairs)) # convert from a list of (elem, cnt) pairs
c.most_common()[-n:] # n least common elements c.most_common()[:-n:-1] # n least common elements
**References**: **References**:
* Wikipedia entry for `Multisets <http://en.wikipedia.org/wiki/Multiset>`_ * Wikipedia entry for `Multisets <http://en.wikipedia.org/wiki/Multiset>`_
* `Bag class <http://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html>`_ * `Bag class <http://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html>`_
in Smalltalk in Smalltalk
* `C++ multisets <http://www.demo2s.com/Tutorial/Cpp/0380__set-multiset/Catalog0380__set-multiset.htm>`_
* `C++ multisets <http://www.demo2s.com/Tutorial/Cpp/0380__set-multiset/Catalog0380__set-multiset.htm>`_
tutorial with standalone examples tutorial with standalone examples
* An early Python `Bag <http://code.activestate.com/recipes/259174/>`_ recipe * An early Python `Bag <http://code.activestate.com/recipes/259174/>`_ recipe
for Python 2.4 and a `Counter <http://code.activestate.com/recipes/576611/>`_ for Python 2.4 and a `Counter <http://code.activestate.com/recipes/576611/>`_
comformant recipe for Python 2.5 and later comformant recipe for Python 2.5 and later
* Use cases for multisets and mathematical operations on multisets. * Use cases for multisets and mathematical operations on multisets.
Knuth, Donald. The Art of Computer Programming Volume II, Knuth, Donald. The Art of Computer Programming Volume II,
Section 4.6.3, Exercise 19 Section 4.6.3, Exercise 19
.. _deque-objects: .. _deque-objects:
:class:`deque` objects :class:`deque` objects