From 601423585f8598d65c8db748d49e4c5225c9e6df Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Fri, 2 Apr 2010 04:16:13 +0000 Subject: [PATCH] Add and update itertools recipes. --- Doc/library/itertools.rst | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index 84f42311bb3..bb1208c363c 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -455,7 +455,7 @@ loops that truncate the stream. def product(*args, repeat=1): # product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy # product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111 - pools = map(tuple, args) * repeat + pools = [tuple(pool) for pool in args] * repeat result = [[]] for pool in pools: result = [x+[y] for x in result for y in pool] @@ -617,7 +617,8 @@ which incur interpreter overhead. return sum(map(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. @@ -703,6 +704,27 @@ which incur interpreter overhead. except exception: pass + def random_product(*args, repeat=1): + "Random selection from itertools.product(*args, **kwds)" + pools = [tuple(pool) for pool in args] * repeat + return [random.choice(pool) for pool in pools] + + def random_permuation(iterable, r=None): + "Random selection from itertools.permutations(iterable, r)" + pool = tuple(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 = tuple(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 = tuple(iterable) + return sorted(map(random.choice, repeat(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::