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Minor doc tweaks.

This commit is contained in:
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('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
a zero count for missing items (instead of raising a :exc:`KeyError` like a
dictionary would)::
>>> c = Counter(['if', 'your', 'peril', 'be'])
>>> c['questions'] # count of a missing element is zero
>>> c = Counter(['egg', 'ham'])
>>> c['bacon'] # count of a missing element is zero
0
Assigning a count of zero or reducing the count to zero leaves the
element in the dictionary. Use ``del`` to remove the entry entirely:
>>> c = Counter(['arthur', 'gwain'])
>>> c['arthur'] = 0 # set the count of "arthur" to zero
>>> 'arthur' in c # but "arthur" is still in the counter
>>> c['arthur'] = 0 # set the count of 'arthur' to zero
>>> 'arthur' in c # but 'arthur' is still in the counter
True
>>> del c['arthur'] # del will completely remove the entry
>>> 'arthur' in c
False
.. versionadded:: 2.7
@ -267,27 +265,27 @@ Common patterns for working with :class:`Counter` objects::
dict(c) # convert to a regular dictionary
c.items() # convert to 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**:
* 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
* `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
* 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/>`_
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,
Section 4.6.3, Exercise 19
.. _deque-objects:
:class:`deque` objects