How can I add several help arguments using argparse, which don't require adding any required arguments?

Question

I'm using ArgumentParser to document the usage of a complicated program. Since the program has several long lists of capabilities, it requires several --help arguments.

My current ArgumentParser looks like this.

parser = ArgumentParser(description = 'Complicated program')
parser.add_argument('--list-models', action = 'store_true', help = 'List the available models')
parser.add_argument('--list-stuff', action = 'store_true', help = 'List the other stuff')
# ...
parser.add_argument('important_data', help = 'Some important data that is required')

I want --list-models and --list-stuff to print some data and exit, similar to how --help works.

However, running the program with either argument fails since important_data is a positional argument, which ArgumentParser always requires.

What's the nicest way to implement this help pattern?

Answer 1

My approach is to make --important-data optional and check afterward:

from argparse import ArgumentParser
import sys

parser = ArgumentParser(description="Complicated program")
parser.add_argument(
    "--list-models", action="store_true", help="List the available models"
)
parser.add_argument("--list-stuff", action="store_true", help="List the other stuff")
# ...
parser.add_argument(
    "important_data", nargs="?", help="Some important data that is required"
)

options = parser.parse_args()
print(f"{options=}")

if options.important_data is None and not options.list_models and not options.list_stuff:
    parser.print_help()
    sys.exit(1)

if options.list_models:
    print("list models")
    sys.exit(0)
    
if options.list_stuff:
    print("list stuff")
    sys.exit(0)

# The rest of the code