NoneType 类型的对象没有 len [英] object of type NoneType has no len

问题描述

def medianeven (L):
    while len(L) > 2:
        L = L[1:(len(L)-1)]
    return average (L)

def medianodd (L):
    while len(L) > 1:
        L = L[1:(len(L)-1)]
    return L[0]

def median (L):
    new = L.sort()
    a = len(new)
    if a % 2 == 0:
        medianeven(new)
    else:
        medianodd(new)

它说 TypeError: object of type 'NoneType' has no len().medianeven 和 medianodd 都有效，但 median 本身不起作用.

It says TypeError: object of type 'NoneType' has no len(). Both medianeven and medianodd work, but median itself is not functioning.

推荐答案

.sort() 就地并返回 None.

更改这一行:

new = L.sort()

就这样:

L.sort()

并用 L 替换所有 new 实例.您还需要返回这些函数调用的结果:

And replace all of your instances of new with just L. You also need to return the results of those function calls:

if a % 2 == 0:
    return medianeven(new)
else:
    return medianodd(new)

另外，Python 的切片支持负索引，所以这段代码:

Also, Python's slices support negative indices, so this code:

L[1:(len(L)-1)]

可以简化为只是

L[1:-1]

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