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)
View Code

 

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')

 

3. 组合

　combinations(iterable, r)

1 from itertools import combinations
2 
3 for x in combinations('ABCD',2):
4     print(x)
5 for x in combinations([1,2,3,4],2):
6     print(x)

 结果

('A', 'B')
('A', 'C')
('B', 'C')
(1, 2)
(1, 3)
(2, 3)

 

 

未完待续...

 

posted @ 2016-12-14 01:01  welcome_home  阅读(326)  评论(0)  编辑  收藏  举报