See here for context.

#!/usr/bin/env /usr/local/bin/python

import sys, email

msg = email.message_from_string(sys.stdin.read())

for part in msg.walk():
  if part.get_content_type() == 'text/calendar':
    f = open(part.get_filename(), 'w')
    f.write(part.get_payload())
    f.close()