其他
一个超好用的Python库：itertools
>>> import itertools>>> x = itertools.accumulate(range(10))>>> print(list(x))[0, 1, 3, 6, 10, 15, 21, 28, 36, 45]>>> x = itertools.chain(range(3), range(4), [3,2,1])>>> print(list(x))[0, 1, 2, 0, 1, 2, 3, 3, 2, 1]>>> x = itertools.combinations(range(4), 3)>>> print(list(x))[(0, 1, 2), (0, 1, 3), (0, 2, 3), (1, 2, 3)]>>> x = itertools.combinations_with_replacement( ABC , 2)>>> print(list(x))[( A , A ), ( A , B ), ( A , C ), ( B , B ), ( B , C ), ( C , C )]>>> x = itertools.compress(range(5), (True, False, True, True, False))>>> print(list(x))[0, 2, 3]>>> x = itertools.count(start=20, step=-1)>>> print(list(itertools.islice(x, 0, 10, 1)))[20, 19, 18, 17, 16, 15, 14, 13, 12, 11]>>> x = itertools.cycle( ABC )>>> print(list(itertools.islice(x, 0, 10, 1)))[ A , B , C , A , B , C , A , B , C , A ]>>> x = itertools.dropwhile(lambda e: e < 5, range(10))>>> print(list(x))[5, 6, 7, 8, 9]>>> x = itertools.filterfalse(lambda e: e < 5, (1, 5, 3, 6, 9, 4))>>> print(list(x))[5, 6, 9]>>> x = itertools.groupby(range(10), lambda x: x < 5 or x > 8) >>> for condition, numbers in x: ... print(condition, list(numbers)) True [0, 1, 2, 3, 4] False [5, 6, 7, 8] True [9]>>> x = itertools.islice(range(10), 0, 9, 2)>>> print(list(x))[0, 2, 4, 6, 8]>>> x = itertools.permutations(range(4), 3)>>> print(list(x))[(0, 1, 2), (0, 1, 3), (0, 2, 1), (0, 2, 3), (0, 3, 1), (0, 3, 2), (1, 0, 2), (1, 0, 3), (1, 2, 0), (1, 2, 3), (1, 3, 0), (1, 3, 2), (2, 0, 1), (2, 0,3), (2, 1, 0), (2, 1, 3), (2, 3, 0), (2, 3, 1), (3, 0, 1), (3, 0, 2), (3, 1, 0), (3, 1, 2), (3, 2, 0), (3, 2, 1)]>>> x = itertools.product( ABC , range(3))>>>>>> print(list(x))[( A , 0), ( A , 1), ( A , 2), ( B , 0), ( B , 1), ( B , 2), ( C , 0), ( C , 1), ( C , 2)]>>> x = itertools.repeat(0, 5)>>> print(list(x))[0, 0, 0, 0, 0]>>> x = itertools.starmap(str.islower, aBCDefGhI )>>> print(list(x))[True, False, False, False, True, True, False, True, False]>>> x = itertools.takewhile(lambda e: e < 5, range(10))>>> print(list(x))[0, 1, 2, 3, 4]>>> x = itertools.tee(range(10), 2)>>> for letters in x:... print(list(letters))...[0, 1, 2, 3, 4, 5, 6, 7, 8, 9][0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>>> x = itertools.zip_longest(range(3), range(5))>>> y = zip(range(3), range(5))>>> print(list(x))[(0, 0), (1, 1), (2, 2), (None, 3), (None, 4)]>>> print(list(y))[(0, 0), (1, 1), (2, 2)]