问Python应用程序错误(Udacity)

EN

    import webapp2

form="""  
<form method="post">
    What is your birthday?
    <br>
    <label>Month<input type="type" name="month"></label>
    <label>Day<input type="type" name="day"></label>
    <label>Year<input type="type" name="year"></label>
    <div style="color: red">%(error)s</div>
    <br>
    <br>
    <input type="submit">
</form> 
"""
def valid_year(year):
        if year and year.isdigit():
            year = int(year)
            if year > 1900 and year < 2020:
                return year

def valid_day(day):
        if day and day.isdigit():
            day = int(day)
            if day > 0 and day <= 31:
                return day

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


    month_abbvs = dict((m[:3].lower(),m) for m in months)

def valid_month(month):
        if month:
            short_month =  month[:3].lower()
            return month_abbvs.get(short_month)

class MainPage(webapp2.RequestHandler):

    def write_form(self, error=""):
        self.response.out.write(form % {"error": error})

    def get(self):
        self.write_form()
        self.valid_year(year)
        self.valid_day(day)
        self.valid_month(month)


    def post(self):
        user_month = valid_month(self.request.get('month'))
        user_day = valid_day(self.request.get('day'))
        user_year = valid_year(self.request.get('year'))
        if not (user_month and user_day and user_year):
            self.write_form("That doesn't look valid to me, friend.")
        else:
            self.response.out.write("Thanks! That's a totally valid day!")

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