itertools

0. Python中引入itertools

1. 笛卡尔积:

　product(iter1, iter2,...,iterN,[repeat=i])

 1 from itertools import product
 2
 3 #笛卡尔积
 4 #3种常见的iter类型
 5 for x in product(‘10‘,repeat=3):
 6     print(x)
 7 for x in product([1,0],repeat=3):
 8     print(x)
 9 for x in product((0,1),repeat=3):
10     print(x)

结果

 1 (‘1‘, ‘1‘, ‘1‘)
 2 (‘1‘, ‘1‘, ‘0‘)
 3 (‘1‘, ‘0‘, ‘1‘)
 4 (‘1‘, ‘0‘, ‘0‘)
 5 (‘0‘, ‘1‘, ‘1‘)
 6 (‘0‘, ‘1‘, ‘0‘)
 7 (‘0‘, ‘0‘, ‘1‘)
 8 (‘0‘, ‘0‘, ‘0‘)
 9
10 (1, 1, 1)
11 (1, 1, 0)
12 (1, 0, 1)
13 (1, 0, 0)
14 (0, 1, 1)
15 (0, 1, 0)
16 (0, 0, 1)
17 (0, 0, 0)
18
19 (0, 0, 0)
20 (0, 0, 1)
21 (0, 1, 0)
22 (0, 1, 1)
23 (1, 0, 0)
24 (1, 0, 1)
25 (1, 1, 0)
26 (1, 1, 1)

复杂示例

lucky+=[int(‘‘.join([str(y) for y in x])) for x in list(product([4,7],repeat=i))]

2.全排列

　permutations(iterable,[,r])

1 from itertools import permutations
2
3 for x in permutations(‘ABC‘):
4     print(x)

结果

(‘A‘, ‘B‘, ‘C‘)
(‘A‘, ‘C‘, ‘B‘)
(‘B‘, ‘A‘, ‘C‘)
(‘B‘, ‘C‘, ‘A‘)
(‘C‘, ‘A‘, ‘B‘)
(‘C‘, ‘B‘, ‘A‘)

未完待续...