python之permutations和

>>> import itertools

>>> list(itertools.combinations('abc', 2))
[('a', 'b'), ('a', 'c'), ('b', 'c')]
>>> list(itertools.permutations('abc',2))
[('a', 'b'), ('a', 'c'), ('b', 'a'), ('b', 'c'), ('c', 'a'), ('c', 'b')]
>>>