python 推导式多个for循环

示例如下:

In [5]: [(i,j) for i in range(10) for j in range(2) ]                                                                                                                                                                                          
Out[5]: 
[(0, 0),
 (0, 1),
 (1, 0),
 (1, 1),
 (2, 0),
 (2, 1),
 (3, 0),
 (3, 1),
 (4, 0),
 (4, 1),
 (5, 0),
 (5, 1),
 (6, 0),
 (6, 1),
 (7, 0),
 (7, 1),
 (8, 0),
 (8, 1),
 (9, 0),
 (9, 1)]

for i in range(10)可以看作是一个外循环,for j in range(2)看作是一个内循环