python - 在函数中返回一个列表。另外，还有 while 循环的问题

Question

我在 Python 中创建函数时遇到问题。我希望我的功能允许用户在列表中输入单词，并询问用户是否愿意输入其他单词。如果用户输入“n”，我希望该函数返回列表中输入的单词。当我运行该函数时，它会询问用户是否愿意输入两次附加单词。此外，它不会返回列表。

def add_list(x):
    first_list = raw_input('Please input a word to add to a list ')
    x.append(first_list)
    response = None
    while response != 'n':
        response = raw_input('Would you like to enter another word? ')
        if response == 'n':
            print 'Here is the list of words'
            return x            
        else:
            add_list(x)


def main(): 
    add_list(x)


x = []
main()  

Answer 1

如上所述，您的代码不返回任何内容的原因是您实际上并未打印结果。此外，即使您已经说了“n”，它仍然继续询问您是否要输入另一个单词的原因是递归(即您以嵌套方式一遍又一遍地调用该函数(想想Excel 中的嵌套 IF，如果有帮助的话:))。一旦你掌握了基础知识，你就可以阅读更多内容，但现在我会避免它:)

这是一个基本版本的东西，可以做你想做的事情，其中​​的注释有望帮助你理解正在发生的事情:

def add_list():
    # Since you are starting with an empty list and immediately appending
    # the response, you can actually cut out the middle man and create
    # the list with the result of the response all at once (notice how
    # it is wrapped in brackets - this just says 'make a list from the
    # result of raw_input'
    x = [raw_input('Please input a word to add to a list: ')]

    # This is a slightly more idiomatic way of looping in this case. We
    # are basically saying 'Keep this going until we break out of it in
    # subsequent code (you can also say while 1 - same thing).
    while True:
        response = raw_input('Would you like to enter another word? ')

        # Here we lowercase the response and take the first letter - if
        # it is 'n', we return the value of our list; if not, we continue
        if response.lower()[0] == 'n':
            return x
        else:
            # This is the same concept as above - since we  know that we
            # want to continue, we append the result of raw_input to x.
            # This will then continue the while loop, and we will be asked
            # if we want to enter another word.
            x.append(raw_input('Please input a word to add to the list: '))

def main():
    # Here we return the result of the function and save it to my_list
    my_list = add_list()

    # Now you can do whatever you want with the list
    print 'Here is the list of words: ', my_list

main()