argparse example part 2

main.py

#!/usr/bin/env python3
# coding: utf8
import sys
import subprocess
import argparse
from pathlib import Path


def ls(path, flags=None):
    if not flags:
        flags = []
    if ~path.is_dir() or ~path.exists():
        print(f'{path!s} does not exist or is not a directory')
        return 1
    cmd = ['ls'] + flags + [str(path)]
    return subprocess.call(cmd)


def man(what, n=1):
    cmd = ['man'] + [str(n)] + [what]
    return subprocess.call(cmd)


def echo(msg):
    print(msg)
    return 0


def _build_parser():
    parser = argparse.ArgumentParser()
    subcmd = parser.add_subparsers(
        dest='subcmd', help='subcommands', metavar='SUBCOMMAND')
    subcmd.required = True

    # ls
    ls_parser = subcmd.add_parser('ls',
                                  help='listing given directory')
    ls_parser.add_argument('path',
                           type=Path,
                           help='path of the directory',
                           metavar='DIR')
    ls_parser.add_argument('--flag',
                           dest='flags',
                           help='flag for ls command (multiple flag)',
                           action='append')
    # man
    man_parser = subcmd.add_parser('man',
                                   help='show man page')
    man_parser.add_argument('what')
    man_parser.add_argument('-n', type=int, help='section number')

    # echo
    echo_parser = subcmd.add_parser('echo',
                                    help='echo a given message')
    echo_parser.add_argument('msg', help='the message', metavar='\'MESSAGE\'')
    return parser


if __name__ == '__main__':
    parser = _build_parser()
    args = parser.parse_args()

    if args.subcmd == 'ls':
        ret = ls(args.path, args.flags)
    elif args.subcmd == 'man':
        ret = man(args.what, n=args.n)
    else:
        ret = echo(args.msg)

    sys.exit(ret)