>>> from itertools import product
>>> for item in product(['a1', 'a2'], ['b1', 'b2'], ['c1', 'c2']):
... print item
...
('a1', 'b1', 'c1')
('a1', 'b1', 'c2')
('a1', 'b2', 'c1')
('a1', 'b2', 'c2')
('a2', 'b1', 'c1')
('a2', 'b1', 'c2')
('a2', 'b2', 'c1')
('a2', 'b2', 'c2')
看起来您的 a1、a2 等是数字。那也很好
>>> from itertools import product
>>> for item in product([1, 2], [3, 4], [5, 6]):
... print item, sum(item)
...
(1, 3, 5) 9
(1, 3, 6) 10
(1, 4, 5) 10
(1, 4, 6) 11
(2, 3, 5) 10
(2, 3, 6) 11
(2, 4, 5) 11
(2, 4, 6) 12