python print usage example

Example 1: argparse accept only few options

...
parser.add_argument('--val',
                    choices=['a', 'b', 'c'],
                    help='Special testing value')

args = parser.parse_args(sys.argv[1:])

Example 2: python argparser flags

parser.add_argument("-v", "--verbose", action="store_true",
                    help="verbose output")