Python:如何在嵌套for循环中增加内循环和外循环

Question

我想用x和z来计算y的值，给出x的范围是1-5，z在2-6之间。还需要注意的是，x控制着外部循环。我的代码的问题是内部for循环不迭代。

x = 1
for x in range(1, 6, 1):
    for z in range(2, 6, 1):
        if(x==z):
           print("Function undefined")
        else:
           y =(float)(x*z)/(x-z)    
        print("When x = ",x ,", z =",z , "then y =",y)
        break        

Answer 1

你的代码就快到了。

您所需要做的就是删除break语句，该语句在第一次迭代中退出内部z循环(每次2次)。

结果会是这样：

When x =  1 , z = 2 then y = -2.0
When x =  1 , z = 3 then y = -1.5
When x =  1 , z = 4 then y = -1.3333333333333333
When x =  1 , z = 5 then y = -1.25
Function undefined
When x =  2 , z = 2 then y = -1.25
When x =  2 , z = 3 then y = -6.0
When x =  2 , z = 4 then y = -4.0
When x =  2 , z = 5 then y = -3.3333333333333335
When x =  3 , z = 2 then y = 6.0
Function undefined
When x =  3 , z = 3 then y = 6.0
When x =  3 , z = 4 then y = -12.0
When x =  3 , z = 5 then y = -7.5
When x =  4 , z = 2 then y = 4.0
When x =  4 , z = 3 then y = 12.0
Function undefined
When x =  4 , z = 4 then y = 12.0
When x =  4 , z = 5 then y = -20.0
When x =  5 , z = 2 then y = 3.3333333333333335
When x =  5 , z = 3 then y = 7.5
When x =  5 , z = 4 then y = 20.0
Function undefined
When x =  5 , z = 5 then y = 20.0

Answer 2

作为另一种选择，如果您实际上不需要打印"Function undefined" (调试除外)，我们可以迭代生成器表达式来创建所有的x、y、z数字。

>>> for x, y, z in ((x, y, z) for x in range(1, 6, 1)
...                           for z in range(2, 6, 1)
...                           if x != z
...                           for y in [(x*z) / (x-z)]):
...   print(f"When x = {x}, z = {z}, then y = {y}")
... 
When x = 1, z = 2, then y = -2.0
When x = 1, z = 3, then y = -1.5
When x = 1, z = 4, then y = -1.3333333333333333
When x = 1, z = 5, then y = -1.25
When x = 2, z = 3, then y = -6.0
When x = 2, z = 4, then y = -4.0
When x = 2, z = 5, then y = -3.3333333333333335
When x = 3, z = 2, then y = 6.0
When x = 3, z = 4, then y = -12.0
When x = 3, z = 5, then y = -7.5
When x = 4, z = 2, then y = 4.0
When x = 4, z = 3, then y = 12.0
When x = 4, z = 5, then y = -20.0
When x = 5, z = 2, then y = 3.3333333333333335
When x = 5, z = 3, then y = 7.5
When x = 5, z = 4, then y = 20.0