itertools

Posted 2020-08-23 welcome_home

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...