[Python-checkins] r79568 - python/branches/release26-maint/Doc/library/itertools.rst
raymond.hettinger
python-checkins at python.org
Fri Apr 2 04:37:34 CEST 2010
Author: raymond.hettinger
Date: Fri Apr 2 04:37:33 2010
New Revision: 79568
Log:
Add and update itertools recipes.
Modified:
python/branches/release26-maint/Doc/library/itertools.rst
Modified: python/branches/release26-maint/Doc/library/itertools.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/itertools.rst (original)
+++ python/branches/release26-maint/Doc/library/itertools.rst Fri Apr 2 04:37:33 2010
@@ -669,7 +669,8 @@
return sum(imap(operator.mul, vec1, vec2))
def flatten(listOfLists):
- return list(chain.from_iterable(listOfLists))
+ "Flatten one level of nesting"
+ return chain.from_iterable(listOfLists)
def repeatfunc(func, times=None, *args):
"""Repeat calls to func with specified arguments.
@@ -778,6 +779,27 @@
except exception:
pass
+ def random_product(*args, **kwds):
+ "Random selection from itertools.product(*args, **kwds)"
+ pools = map(tuple, args) * kwds.get('repeat', 1)
+ return map(random.choice, pools)
+
+ def random_permuation(iterable, r=None):
+ "Random selection from itertools.permutations(iterable, r)"
+ pool = list(iterable)
+ r = len(pool) if r is None else r
+ return random.sample(pool, r)
+
+ def random_combination(iterable, r):
+ "Random selection from itertools.combinations(iterable, r)"
+ pool = list(iterable)
+ return sorted(random.sample(pool, r), key=pool.index)
+
+ def random_combination_with_replacement(iterable, r):
+ "Random selection from itertools.combinations_with_replacement(iterable, r)"
+ pool = list(iterable)
+ return sorted(imap(random.choice, [pool]*r), key=pool.index)
+
Note, many of the above recipes can be optimized by replacing global lookups
with local variables defined as default values. For example, the
*dotproduct* recipe can be written as::
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