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Code Issues Releases Wiki Activity

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) pools = map(tuple, args) * kwds.get('repeat', 1)
return tuple(random.choice(pool) for pool in pools) 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)" "Random selection from itertools.permutations(iterable, r)"
pool = tuple(iterable) pool = tuple(iterable)
r = len(pool) if r is None else r r = len(pool) if r is None else r
@ -805,12 +805,16 @@ which incur interpreter overhead.
def random_combination(iterable, r): def random_combination(iterable, r):
"Random selection from itertools.combinations(iterable, r)" "Random selection from itertools.combinations(iterable, r)"
pool = tuple(iterable) 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): def random_combination_with_replacement(iterable, r):
"Random selection from itertools.combinations_with_replacement(iterable, r)" "Random selection from itertools.combinations_with_replacement(iterable, r)"
pool = tuple(iterable) 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 Note, many of the above recipes can be optimized by replacing global lookups
with local variables defined as default values. For example, the with local variables defined as default values. For example, the