code: def request_host(request):
      
      url = request.get_full_url()
      parse_result = compat.urlparse.urlparse(url)
      scheme, host, port = parse_result.scheme, parse_result.hostname, parse_result.port
      try:
          port = int(port)
      except ValueError:
          pass
      if host == "":
          host = request.get_header("Host", "")
  
      if port != default_ports.get(scheme):
          host = "%s:%s" % (host, port)
      return host
docs: Return request-host, as defined by RFC 2965.
  
      Variation from RFC: returned value is lowercased, for convenient
      comparison.