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python双重for循环怎么理解
栏目分类:python问答   发布日期:2019年06月01日 15:15:13   浏览次数:

所谓的双重循环,就是二层循环的意思,外面一层循环,里面一层循环,又叫循环嵌套,有的时候,还可以更多层循环嵌套


python双重for循环格式:

 

    for 条件 1:                        外层循环

       for 条件 2:                     内层循环

           循环体

特点:
外层循环一次,内层循环一遍

例子:来看下面的九成九乘法表,可以更好的理解,有9行,有9列,如果是一层循环,外层循环控制行,内层循环控制列
 

1 x 1 = 1

1 x 2 = 2 2 x 2 = 4

1 x 3 = 3 2 x 3 = 6 3 x 3 = 9

1 x 4 = 4 2 x 4 = 8 3 x 4 = 12 4 x 4 = 16

1 x 5 = 5 2 x 5 = 10 3 x 5 = 15 4 x 5 = 20 5 x 5 = 25

1 x 6 = 6 2 x 6 = 12 3 x 6 = 18 4 x 6 = 24 5 x 6 = 30 6 x 6 = 36

1 x 7 = 7 2 x 7 = 14 3 x 7 = 21 4 x 7 = 28 5 x 7 = 35 6 x 7 = 42 7 x 7 = 49

1 x 8 = 8 2 x 8 = 16 3 x 8 = 24 4 x 8 = 32 5 x 8 = 40 6 x 8 = 48 7 x 8 = 56 8 x 8 = 64

1 x 9 = 9 2 x 9 = 18 3 x 9 = 27 4 x 9 = 36 5 x 9 = 45 6 x 9 = 54 7 x 9 = 63 8 x 9 = 72 9 x 9 = 81

 
 

相关实现代码:
 

for i in range(1,10):

    for j in range(1,i+1):#(1,2) i1,2

        print('%d x %d = %d\t'%(j,i,i*j),end='')

    print()

运行结果如下:

1 x 1 = 1

1 x 2 = 2 2 x 2 = 4

1 x 3 = 3 2 x 3 = 6 3 x 3 = 9

1 x 4 = 4 2 x 4 = 8 3 x 4 = 12 4 x 4 = 16

1 x 5 = 5 2 x 5 = 10 3 x 5 = 15 4 x 5 = 20 5 x 5 = 25

1 x 6 = 6 2 x 6 = 12 3 x 6 = 18 4 x 6 = 24 5 x 6 = 30 6 x 6 = 36

1 x 7 = 7 2 x 7 = 14 3 x 7 = 21 4 x 7 = 28 5 x 7 = 35 6 x 7 = 42 7 x 7 = 49

1 x 8 = 8 2 x 8 = 16 3 x 8 = 24 4 x 8 = 32 5 x 8 = 40 6 x 8 = 48 7 x 8 = 56 8 x 8 = 64

1 x 9 = 9 2 x 9 = 18 3 x 9 = 27 4 x 9 = 36 5 x 9 = 45 6 x 9 = 54 7 x 9 = 63 8 x 9 = 72 9 x 9 = 81

 

 


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