Simple application made using webapp2

main.py

#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import webapp2

form = """
<form method="post">
    What is your birthday?
    <br>

    <label>Month
        <input type="text" name="month">
    </label>
    
    <label>Day
        <input type="text" name="day">
    </label>
    
    <label>Year
        <input type="text" name="year">
    </label>

    <div style="color: red">%(error)s</div> 

    <br>
    <br>
    <input type="submit">
</form>
"""
def valid_month(month):
    months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
    abbvs_month = dict((m[:3].lower(), m) for m in months)
    if month:
        short_month = month[:3].lower()
        return abbvs_month.get(short_month)

def valid_day(day):
    if day and day.isdigit():
        int_day = int(day)
        if 0 < int_day and int_day < 31:
            return int_day
            return None

def valid_year(year):
    if year and year.isdigit():
        int_year = int(year)
        if 1900 <= int_year and int_year <= 2020:
            return int_year
            return None


class MainPage(webapp2.RequestHandler):
    def write_form(self, error=""):
        self.response.out.write(form % {"error": error})

    def get(self):
        self.write_form()

    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...")
        else:
            self.response.out.write("Thanks!")

class Welcome(webapp2.RequestHandler):
    def get(self):
        username = self.request.get('username')
        if valid_username(username):
            self.render('welcome.html', username = username)
        else:
            self.redirect('/')

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