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Code Issues Releases Wiki Activity

Cleanup itertools recipes

This commit is contained in:
Raymond Hettinger 2010-04-02 06:23:12 +00:00
parent 4bfd3bda2e
commit f28dd0d1bf
1 changed files with 8 additions and 8 deletions
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16
Doc/library/itertools.rst
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@ -697,7 +697,7 @@ which incur interpreter overhead.
def ncycles(iterable, n):
"Returns the sequence elements n times"
return chain.from_iterable(repeat(iterable, n))
return chain.from_iterable(repeat(tuple(iterable), n))
def dotproduct(vec1, vec2):
return sum(imap(operator.mul, vec1, vec2))
@ -794,23 +794,23 @@ which incur interpreter overhead.
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)
return tuple(random.choice(pool) for pool in pools)
def random_permuation(iterable, r=None):
"Random selection from itertools.permutations(iterable, r)"
pool = list(iterable)
pool = tuple(iterable)
r = len(pool) if r is None else r
return random.sample(pool, r)
return tuple(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)
pool = tuple(iterable)
return tuple(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)
pool = tuple(iterable)
return tuple(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