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Fixup new itertools recipes.

This commit is contained in:
Raymond Hettinger 2010-04-10 07:01:32 +00:00
parent 343314a11c
commit a1d61d0495
1 changed files with 7 additions and 3 deletions
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10
Doc/library/itertools.rst
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@ -796,7 +796,7 @@ which incur interpreter overhead.
pools = map(tuple, args) * kwds.get('repeat', 1)
return tuple(random.choice(pool) for pool in pools)
def random_permuation(iterable, r=None):
def random_permutation(iterable, r=None):
"Random selection from itertools.permutations(iterable, r)"
pool = tuple(iterable)
r = len(pool) if r is None else r
@ -805,12 +805,16 @@ which incur interpreter overhead.
def random_combination(iterable, r):
"Random selection from itertools.combinations(iterable, r)"
pool = tuple(iterable)
return tuple(sorted(random.sample(pool, r), key=pool.index))
n = len(pool)
indices = sorted(random.sample(xrange(n), r))
return tuple(pool[i] for i in indices)
def random_combination_with_replacement(iterable, r):
"Random selection from itertools.combinations_with_replacement(iterable, r)"
pool = tuple(iterable)
return tuple(sorted(imap(random.choice, [pool]*r), key=pool.index))
n = len(pool)
indices = sorted(random.randrange(n) for i in xrange(r))
return tuple(pool[i] for i in indices)
Note, many of the above recipes can be optimized by replacing global lookups
with local variables defined as default values. For example, the