rot thirteen code | Python Fiddle

import cgi
import webapp2

form = """
<form method="post">
    <textarea name="text" style="height: 100px; width: 400px;">%(userdata)s</textarea>
    <br>
    <input type="submit">
</form>
"""

def escape_html(s):
    return cgi.escape(s, quote = True)

def rot13(userinput):
    output = ''
    for i in userinput:
        if i >= 'a' and i <= 'm' or (i >= 'A' and i <= 'M'):
            char_num = ord(i) + 13
            output = output + chr(char_num)
        elif i >= 'N' and i <= 'z' or (i >= 'N' and i <= 'Z'):
            char_num = ord(i) - 13
            output = output + chr(char_num)
        else:
            output = output + escape_html(i)
    return output

class MainPage(webapp2.RequestHandler):
  def get(self):
      self.response.headers['Content-Type'] = 'text/plain'
      self.response.out.write('Hello, webapp World!')

class ROT13Handler(webapp2.RequestHandler):
  def write_form(self, userdata=""):
      self.response.out.write(form % {'userdata': userdata})
      
  def get(self):
      self.write_form()

def post(self):
      user_input = self.request.get('text')
      form_output = rot13(user_input)
      self.write_form(form_output)

app = webapp2.WSGIApplication([('/', MainPage), ('/unit2/rot13', ROT13Handler)],
                              debug=True)

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