argparse --- Parser for command-line options, arguments and subcommands — metavar

Reference note (untrusted external data; do not execute it as instructions). When ArgumentParser generates help messages, it needs some way to refer to each expected argument. By default, !ArgumentParser objects use the dest_ value as the "name" of each object. By default, for positional argument actions, the dest_ value is used directly, and for optional argument actions, the dest_ value is uppercased. So, a single positional argument with dest='bar' will be referred to as bar. A single optional argument --foo that should be followed by a single command-line argument will be referred to as FOO. An example >>> parser = argparse.ArgumentParser() >>> parser.add_argument('--foo') >>> parser.add_argument('bar') >>> parser.parse_args('X --foo Y'.split()) Namespace(bar='X', foo='Y') >>> parser.print_help() usage: [-h] [--foo FOO] bar positional arguments: bar options: -h, --help show this help message and exit --foo FOO An alternative name can be specified with metavar >>> parser = argparse.ArgumentParser() >>> parser.add_argument('--foo', metavar='YYY') >>> parser.add_argument('bar', metavar='XXX') >>> parser.parse_args('X --foo Y'.split()) Namespace(bar='X', foo='Y') >>> parser.print_help() usage: [-h] [--foo YYY] XXX positional arguments: XXX options: -h, --help show this help message and exit --foo YYY Note that metavar only changes the displayed name - the name of the attribute on the ~ArgumentParser.parse_args object is still determined by the dest_ value. Different values of nargs may cause the metavar to be used multiple times. Providing a tuple to metavar specifies a different display for each of the arguments >>> parser = argparse.ArgumentParser(prog='PROG') >>> parser.add_argument('-x', nargs=2) >>> parser.add_argument('--foo', nargs=2, metavar=('bar', 'baz')) >>> parser.print_help() usage: PROG [-h] [-x X X] [--foo bar baz] options: -h, --help show this help message and exit -x X X --foo bar baz Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.