Python で順列と組み合わせメモ

(python2.7)

$ ipython

In [1]: from itertools import combinations, permutations

In [2]: arr = ['a', 'b', 'c', 'd']

In [3]: list(permutations(arr))
Out[3]:
[('a', 'b', 'c', 'd'),
 ('a', 'b', 'd', 'c'),
 ('a', 'c', 'b', 'd'),
 ('a', 'c', 'd', 'b'),
 ('a', 'd', 'b', 'c'),
 ('a', 'd', 'c', 'b'),
 ('b', 'a', 'c', 'd'),
 ('b', 'a', 'd', 'c'),
 ('b', 'c', 'a', 'd'),
 ('b', 'c', 'd', 'a'),
 ('b', 'd', 'a', 'c'),
 ('b', 'd', 'c', 'a'),
 ('c', 'a', 'b', 'd'),
 ('c', 'a', 'd', 'b'),
 ('c', 'b', 'a', 'd'),
 ('c', 'b', 'd', 'a'),
 ('c', 'd', 'a', 'b'),
 ('c', 'd', 'b', 'a'),
 ('d', 'a', 'b', 'c'),
 ('d', 'a', 'c', 'b'),
 ('d', 'b', 'a', 'c'),
 ('d', 'b', 'c', 'a'),
 ('d', 'c', 'a', 'b'),
 ('d', 'c', 'b', 'a')]

In [4]: list(combinations(arr, 2))
Out[4]: [('a', 'b'), ('a', 'c'), ('a', 'd'), ('b', 'c'), ('b', 'd'), ('c', 'd')]