for 循环的嵌套

1. 列表生成式的嵌套 for 循环：

示例如下：

li1 = range(1,6)
li2 = list("ABC")    # list("ABC") 的结果为 ["A", "B", "C"]    

for m in li1:
    for n in li2:
        print((m,n))

li = [(m,n) for m in li1 for n in li2]
print(li)


# 输出结果：
(1, 'A')
(1, 'B')
(1, 'C')
(2, 'A')
(2, 'B')
(2, 'C')
(3, 'A')
(3, 'B')
(3, 'C')
(4, 'A')
(4, 'B')
(4, 'C')
(5, 'A')
(5, 'B')
(5, 'C')
[(1, 'A'), (1, 'B'), (1, 'C'), (2, 'A'), (2, 'B'), (2, 'C'), (3, 'A'), (3, 'B'), (3, 'C'), (4, 'A'), (4, 'B'), (4, 'C'), (5, 'A'), (5, 'B'), (5, 'C')]

# 列表生成式中的 两个 for 循环 作用就相当于 for 循环的嵌套

参考链接： https://www.jb51.net/article/150400.htm