product 笛卡尔积 (有放回抽样排列)
permutations 排列 (不放回抽样排列)
combinations 组合,没有重复 (不放回抽样组合)
combinations_with_replacement 组合,有重复 (有放回抽样组合)
详细的参见官网。
>>> import itertools
>>> for i in itertools.product('ABCD', repeat = 2):
... print(i)
...
('A', 'A') ('A', 'B') ('A', 'C') ('A', 'D') ('B', 'A') ('B', 'B') ('B', 'C') ('B', 'D') ('C', 'A') ('C', 'B') ('C', 'C') ('C', 'D') ('D', 'A') ('D', 'B') ('D', 'C') ('D', 'D')
>>> for i in itertools.permutations('ABCD', 2):
... print(i)
...
('A', 'B') ('A', 'C') ('A', 'D') ('B', 'A') ('B', 'C') ('B', 'D') ('C', 'A') ('C', 'B') ('C', 'D') ('D', 'A') ('D', 'B') ('D', 'C')
>>> for i in itertools.combinations('ABCD', 2):
... print(i)
...
('A', 'B') ('A', 'C') ('A', 'D') ('B', 'C') ('B', 'D') ('C', 'D')
>>> for i in itertools.combinations_with_replacement('ABCD', 2):
... print(i)
...
('A', 'A') ('A', 'B') ('A', 'C') ('A', 'D') ('B', 'B') ('B', 'C') ('B', 'D') ('C', 'C') ('C', 'D') ('D', 'D')