Python argparse required=True but --version functionality?

Question

In all my scripts I use the standard flags --help and --version, however I cannot seem to figure out how to make a --version with parser.add_argument(..., required=True).

import sys, os, argparse  parser = argparse.ArgumentParser(description='How to get --version to work?')  parser.add_argument('--version', action='store_true',                      help='print version information') parser.add_argument('-H', '--hostname', dest='hostname', required=True,                      help='Host name, IP Address') parser.add_argument('-d', '--database', dest='database', required=True,                     help='Check database with indicated name') parser.add_argument('-u', '--username', dest='username', required=True,                      help='connect using the indicated username') parser.add_argument('-p', '--password', dest='password', required=True,                      help='use the password to authenticate the connection')  args = parser.parse_args()  if args.version == True:     print 'Version information here'  $ ./arg.py  --version  usage: arg.py [-h] [--version] -H HOSTNAME -d DATABASE -u USERNAME -p PASSWORD  arg.py: error: argument -H/--hostname is required 

Yes, I want --hostname and others required, but I always want --version to work appropriately like --help (and -h).

$ ./arg.py  --help    usage: arg.py [-h] [--version] -H HOSTNAME -d DATABASE -u USERNAME -p PASSWORD  How to get --version to work?  optional arguments:   -h, --help            show this help message and exit   --version             print version information   -H HOSTNAME, --hostname HOSTNAME                         Host name, IP Address   -d DATABASE, --database DATABASE                         Check database with indicated name   -u USERNAME, --username USERNAME                         connect using the indicated username   -p PASSWORD, --password PASSWORD                         use the password to authenticate the connection 

Any help on getting --version to work?

Answer 1

There is a special version action keyword argument to add_argument (As documented here: argparse#action).
Try this (copied from working code):

parser.add_argument('-V', '--version',                      action='version',                                         version='%(prog)s (version 0.1)')