Post方法重新发送表单而不是写出消息

Question

我一直在这个上拉头发30分钟，我不知道我做错了什么，因为没有语法错误但是post方法在它应该写出消息时继续重新发送表单else声明

main.py

import webapp2
import dateValidation

form = """
<form>
<input type="text name="month">
<input type="text name="day">
<input type="text name="year">
<input type="submit">
</form>>

"""

class MainPage(webapp2.RequestHandler):
  def get(self):
        self.response.out.write(form)

  def post(self):
        user_month=dateValidation.valid_month(self.request.get('month'))
        user_day=dateValidation.valid_day(self.request.get('day'))
        user_year=dateValidation.valid_year(self.request.get('year'))

        if not (user_month and user_day and user_year):
            self.response.out.write(form)
        else:
            self.response.out.write("Thanks, that's a totally valid day!")

app = webapp2.WSGIApplication([('/', MainPage)],
                               debug=True)

dateValidation.py：

months = ['January',
          'February',
          'March',
          'April',
          'May',
          'June',
          'July',
          'August',
          'September',
          'October',
          'November',
          'December']

def valid_month(month):
    if month:
        cap_Month=month.capitalize()
        if cap_month in months:
          return cap_month

def valid_day(day):
    if day and day.isdigit():
        day=int(day)
        if day>0 and day<32:
            return day

def valid_year(year):
    if year and year.isdigit():
        year=int(year)
        if year>1920 and year<2020:
            return year