Python：函数不会返回值

我有一段代码，它遍历用户的输入并返回输出

while True:

  city = input("Enter city.")
  if city in city_list:
    print (city,'selected')
    break
 else:
   print ('Please try again.')

由于我多次请求输入，它看起来是多余的，我试图将它封装在一个函数中，下面是整个函数

def get_filters():
    print ('Welcome .')

    #list for month and day data_user
    city_list=['city1','city2','city3']
    month_list=['January', 'February', 'March', 'April', 'May','June','All']
    day_list=['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday','All']

    city_string=('Enter city.')
    city=None
    month_string=('Enter month.')
    month=None
    day_string=('Enter day.')
    day=None

    def check_input(data, s_string, data_list):
        while True:
            data = input(s_string)
            if data in data_list:
                print (data,'selected')
                return data
                break
            else:
                print ('Please try again.')

    check_input(city, city_string, city_list)
    check_input(month, month_string, month_list)
    check_input(day, day_string, day_list)

    return city, month, day

如果我运行代码，我会收到一条错误消息，在代码的后面无法加载这些值。城市、日期和月份不会被传递。

---

我返回值的方式有问题吗？

假设您想捕获 用户输入的三个选项。下面是python3下的工作代码。请试试这个

#!/usr/local/Cellar/python/3.6.5/bin/python3

def get_filters():
    print ('Welcome .')

#list for month and day data_user
city_list=['city1','city2','city3']
month_list=['January', 'February', 'March', 'April', 'May','June','All']
day_list=['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday','All']

city_string=('Enter city.')
city=None
month_string=('Enter month.')
month=None
day_string=('Enter day.')
day=None

def check_input(data, s_string, data_list):
  while True:
      data = input(s_string)
      if data in data_list:
          print (data)
          return data
          break
      else:
          print ('Please try again.')

selection = (check_input(city, city_string, city_list) , check_input(month, month_string, month_list) , check_input(day, day_string, day_list))

print (selection)


---Output--- 
    Enter city.city1
    city1
    Enter month.January
    January
    Enter day.Monday
    Monday
   ('city1', 'January', 'Monday')

---

您的缩进在此关闭，请修复此问题并发布您收到的整个错误。您不保存检查输入报告的值：您需要执行：city=check\u inputcity，city\u string，city\u list。您的城市内部检查输入不在更高功能的范围内，因此对于更高功能，城市仍然为零