import argparse

def foo(names=[]):
    parser = argparse.ArgumentParser(help_groups=names)
    parser.add_argument('pos', help='required positional')
    group = parser.add_argument_group('user group')
    parser.add_argument('-f', '--foo', help='optional')
    parser.add_argument('-g', '--goo', required=True, help='required optional')
    group.add_argument('--garg', help='group arg')
    parser.add_argument('baz', nargs='?', help='optional positional')
    parser.print_help()
    print(parser.parse_args('-f FOO -g GOO pos baz'.split()))
    print()

for names in ['', 'all',
              'positionals optionals',
              'positionals required optionals']:
    foo(names.split())

"""
usage: alt_grouping2.py [-h] [-f FOO] -g GOO [--garg GARG] pos [baz]

positionals:
  pos                required positional
  baz                optional positional

required:
  -g GOO, --goo GOO  required optional

optionals:
  -h, --help         show this help message and exit
  -f FOO, --foo FOO  optional

user group:
  --garg GARG        group arg
"""