Mixture of sub-command and root arguments in Argument Parser

Question

Here are two possible ways to run a Python program with arguments

python ./main.py setup-queues

or

python ./main.py -n 2 -i 1

If the sub-command setup-queues is not given, root arguments -n & -i must be provided.

On the other hand, setup-queues must be given when the root arguments are missing.

Here is my initial code to do argument parsers

if __name__ == '__main__':
    parser = argparse.ArgumentParser(prog='Hello')
    num_arg = parser.add_argument("-n", "--number", type=int) 
    parser.add_argument("-i", "--index", type=int)
       subparsers = parser.add_subparsers(help='sub-command help')
    
    # setup queue
    queue_parser = subparsers.add_parser("setup-queues")
    queue_parser.set_defaults(func=setup_queue)

    args = parser.parse_args()
    args.func(args)

    # raising error in case of number is zero
    if args.number == 0:
       raise argparse.ArgumentError(num_arg, f"{num_arg.dest} argument should be more than zero!")

    print(f"Given parameter: n: {args.number} & i: {args.index}")

When the command line is python ./main.py setup-queues: I expect the code to run only setup_queue when sub-command setup-queues is given. However, the code keeps running till the final line. I expect it to run only setup-queue method & exit.

When the command line is python ./main.py -n 2 -i 1 I expect the code runs till the final line.

Is there a better way to handle sub-command & root arguments?

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