Attempt to answer https://stackoverflow.com/q/52838014/3135417

subparsers.py

#!/usr/bin/env python3
"""
Script to test or run commands on given servers.
./this_script.py test  # To test all servers
./this_script.py run --id 127.0.0.1 --command "echo hello world"
"""
from argparse import ArgumentParser, RawDescriptionHelpFormatter as RDHF


def test_servers(servers):
    """
    Given a list of servers, let's test them!
    """
    for server in servers:
        print('Just tested server {s}'.format(s=server))

def do_actual_work(server_id, command):
    """
    Given a server ID and a command, let's run the command on that server!
    """
    print('Connected to server {s}'.format(s=server_id))
    print('Ran command {c} successfully'.format(c=command))


if __name__ == '__main__':
    parser = ArgumentParser(description=__doc__, formatter_class=RDHF)
    subs = parser.add_subparsers()
    subs.required = True
    subs.dest = 'run or test'
    test_parser = subs.add_parser('test', help='Test all servers')
    test_parser.set_defaults(func=test_servers)
    run_parser = subs.add_parser('run', help='Run a command on the given server')
    run_parser.add_argument('-i', '--id',
                            help='The ID of the server to connect to and run commands',
                            required=True)
    run_parser.add_argument('-c', '--command',
                            help='The command to run',
                            required=True)
    run_parser.set_defaults(func=do_actual_work)
    args = parser.parse_args()
    
    if args.func.__name__ == 'test_servers':
        all_servers = ['127.0.0.1', '127.0.0.2']
        test_servers(all_servers)
    else:
        do_actual_work(args.id, args.command)