为什么“返回 list.sort()"?返回无，而不是列表?

Why does quot;return list.sort()quot; return None, not the list?(为什么“返回 list.sort()?返回无，而不是列表?)

问题描述

我已经能够验证 findUniqueWords 确实会产生一个排序的 list.但是，它不会返回列表.为什么?

I've been able to verify that the findUniqueWords does result in a sorted list. However, it does not return the list. Why?

def findUniqueWords(theList):
    newList = []
    words = []

    # Read a line at a time
    for item in theList:

        # Remove any punctuation from the line
        cleaned = cleanUp(item)

        # Split the line into separate words
        words = cleaned.split()

        # Evaluate each word
        for word in words:

            # Count each unique word
            if word not in newList:
                newList.append(word)

    answer = newList.sort()
    return answer

推荐答案

list.sort 对列表进行就地排序，即不返回新列表.随便写

list.sort sorts the list in place, i.e. it doesn't return a new list. Just write

newList.sort()
return newList

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