new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  from __future__ import absolute_import, division, unicode_literals
  
  # Copyright (C) 2018 Ben McGinnes <ben@gnupg.org>
  #
  # This program is free software; you can redistribute it and/or modify it under
  # the terms of the GNU General Public License as published by the Free Software
  # Foundation; either version 2 of the License, or (at your option) any later
  # version.
  #
  # This program is free software; you can redistribute it and/or modify it under
  # the terms of the GNU Lesser General Public License as published by the Free
  # Software Foundation; either version 2.1 of the License, or (at your option)
  # any later version.
  #
  # This program is distributed in the hope that it will be useful, but WITHOUT
  # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  # FOR A PARTICULAR PURPOSE.  See the GNU General Public License and the GNU
  # Lesser General Public Licensefor more details.
  #
  # You should have received a copy of the GNU General Public License and the GNU
  # Lesser General Public along with this program; if not, see
  # <http://www.gnu.org/licenses/>.
  
  import gpg
  import os.path
  
  print("""
  This script adds a new user ID to an existing key.
  
  The gpg-agent and pinentry are invoked to enter the passphrase.
  """)
  
  c = gpg.Context()
  
  homedir = input("Enter the GPG configuration directory path (optional): ")
  fpr0 = input("Enter the fingerprint of the key to modify: ")
  uid_name = input("Enter the name of the user ID: ")
  uid_email = input("Enter the email address of the user ID: ")
  uid_cmnt = input("Enter a comment to include (optional): ")
  
  if homedir.startswith("~"):
      if os.path.exists(os.path.expanduser(homedir)) is True:
          c.home_dir = os.path.expanduser(homedir)
      else:
          pass
  elif os.path.exists(homedir) is True:
      c.home_dir = homedir
  else:
      pass
  
  fpr = "".join(fpr0.split())
  
  if len(uid_cmnt) > 0:
      userid = "{0} ({1}) <{2}>".format(uid_name, uid_cmnt, uid_email)
  else:
      userid = "{0} <{2}>".format(uid_name, uid_email)
  
  key = c.get_key(fpr, secret=True)
  c.key_add_uid(key, userid)
  
subject: add user ID