def a(i):
    return i + 1

def b(i):
    return i + 2

def c(i):
    return i + 3
funcs = {'a': a, 'b': b, 'c': c}
parser.add_argument('-f', '--func', dest='func', choices=['a', 'b', 'c'],
    required=True, help='Choose one of the specified function to be run.')
args = parser.parse_args()
chosen_func = funcs[args.func]
How to use argparse arguments as function names