a simple app described in https://www.facebook.com/groups/gcpughk/permalink/1856928067665842/

app.yaml

runtime: python27
api_version: 1
threadsafe: true

handlers:
- url: /
  script: main.app

- url: /(.*)
  script: main.app

main.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

import webapp2

class Handler(webapp2.RequestHandler):
  def get(self, num=None):
    if num is None:
      self.response.write('There is nothing here...')
    else:
      self.response.write('{}'.format(num))



# see http://webapp2.readthedocs.io/en/latest/guide/routing.html
      
app = webapp2.WSGIApplication([
    webapp2.Route(r'/', Handler),
    webapp2.Route(r'/<num:\d+>', Handler),
  ], debug=True)