itertools.permutations

通俗地讲，就是返回可迭代对象的所有数学全排列方式。

from itertools import permutations

for item in permutations(['a', 'b', 'c']):
    print(item)

('a', 'b', 'c')
('a', 'c', 'b')
('b', 'a', 'c')
('b', 'c', 'a')
('c', 'a', 'b')
('c', 'b', 'a')

Process finished with exit code 0

from itertools import permutations

for i in permutations('123', 2):
     print(i)

('1', '2')
('1', '3')
('2', '1')
('2', '3')
('3', '1')
('3', '2')

Process finished with exit code 0