Commit ce2338a1 authored by Raymond Hettinger's avatar Raymond Hettinger

Add and update itertools recipes.

parent 11d36bc1
......@@ -669,7 +669,8 @@ which incur interpreter overhead.
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 @@ which incur interpreter overhead.
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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