Python-为什么“ return list.sort（）”返回None，而不返回列表？

Question

我已经能够验证findUniqueWords结果是否为sorted list。但是，它不返回列表。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对列表进行适当排序，即不返回新列表。写吧

newList.sort()
return newList