Code snippet to parse arguments from a config file

python-config-args-parser.py

import argparse
import ConfigParser
import sys
 
def main(argv=None):
    # Do argv default this way, as doing it in the functional
    # declaration sets it at compile time.
    if argv is None:
        argv = sys.argv[1]:
 
    # Parse any conf_file specification
    # Found at: http://stackoverflow.com/a/5826167/613218
    # We make this parser with add_help=False so that
    # it doesn't parse -h and print help.
    config_parser = argparse.ArgumentParser(
        description=__doc__, # printed with -h/--help
        # Don't mess with format of description
        formatter_class=argparse.RawDescriptionHelpFormatter,
        # Turn off help, so we print all options in response to -h
        add_help=False
        )
    config_parser.add_argument("-c", "--config-file",
                        help="Specify config file", metavar="FILE")
    args, remaining_argv = conf_parser.parse_known_args(argv)
 
    if args.config_file:
        config = ConfigParser.SafeConfigParser()
        config.read([args.config_file])
        defaults = dict(config.items("Defaults"))
    else:
        defaults = { "option":"default" }
 
    # Parse rest of arguments
    # Don't suppress add_help here so it will handle -h
    parser = argparse.ArgumentParser(
        # Inherit options from config_parser
        parents=[config_parser]
        )
    parser.set_defaults(**defaults)
    parser.add_argument("--option")
    args = parser.parse_args(remaining_argv)
    print "Option is \"{}\"".format(args.option)
    return(0)
 
if __name__ == "__main__":
    sys.exit(main())