python - 为什么 "return list.sort()"返回 None，而不是列表？

Question

这个问题在这里已经有了答案:

Why do these list operations (methods: clear / extend / reverse / append / sort / remove) return None, rather than the resulting list? (4 个回答)

关闭 3个月前。

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？

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

Answer 1

list.sort 对列表进行就地排序，即它不返回新列表。随便写

newList.sort()
return newList