【Python】itertools之product函數

【轉載】源博客

product 用於求多個可迭代對象的笛卡爾積(Cartesian Product)，它跟嵌套的 for 循環等價.即:

product(A, B) 和 ((x,y) for x in A for y in B)的效果是一樣的。


使用形式如下：

itertools.product(*iterables, repeat=1)

iterables 是可迭代對象, repeat指定 iterable 重復幾次,即:

product(A,repeat=3)等價於product(A,A,A)

 

Coding Time:

>>> from itertools import product as product
>>> A = [1, 2, 3]
>>> B = [100, 200, 300]
>>> for item in product(A, B):
...     print(item)
... 
(1, 100)
(1, 200)
(1, 300)
(2, 100)
(2, 200)
(2, 300)
(3, 100)
(3, 200)
(3, 300)

>>> for item in product(A, repeat=3):
...     print(item)
... 
(1, 1, 1)
(1, 1, 2)
(1, 1, 3)
(1, 2, 1)
(1, 2, 2)
(1, 2, 3)
(1, 3, 1)
(1, 3, 2)
(1, 3, 3)
(2, 1, 1)
(2, 1, 2)
(2, 1, 3)
(2, 2, 1)
(2, 2, 2)
(2, 2, 3)
(2, 3, 1)
(2, 3, 2)
(2, 3, 3)
(3, 1, 1)
(3, 1, 2)
(3, 1, 3)
(3, 2, 1)
(3, 2, 2)
(3, 2, 3)
(3, 3, 1)
(3, 3, 2)
(3, 3, 3)