python - 返回元组的函数给出 TypeError: 'NoneType' object is not iterable

Question

这个错误是什么意思？我正在尝试创建一个返回元组的函数。我确定我做错了。任何帮助表示赞赏。

from random import randint
A = randint(1,3)
B = randint(1,3)
def make_them_different(a,b):
    while a == b:
        a = randint(1,3)
        b = randint(1,3)
        return (a,b)
new_A, new_B = make_them_different(A,B)

Answer 1

您的代码返回Noneif a != b。

因为，你return在 while 循环中有语句，如果 while 循环永远不会被执行，Python 会返回默认值，None它不能被分配给new_A, new_B.

>>> print make_them_different(2, 3)
None

>>> print make_them_different(2, 2)
(2, 1)

您可以通过返回默认值来解决此问题（因为它们不同，这就是您打算做的）

def make_them_different(a,b):
    while a == b:
        a = randint(1,3)
        b = randint(1,3)
    return (a,b)  # Dedented the return line.

演示 -

>>> make_them_different(2, 2)
(3, 2)
>>> make_them_different(2, 3)
(2, 3)

Answer 2

将返回值缩进一级：

from random import randint
A = randint(1,3)
B = randint(1,3)
def make_them_different(a,b):
    while a == b:
        a = randint(1,3)
        b = randint(1,3)
    return (a,b)
new_A, new_B = make_them_different(A,B)

否则 a,b 只会重新生成一次 - 之后它们可能会再次碰撞，因为你永远不会循环。