import argparse


def add(a, b):
    return a + b


def sub(a, b):
    return a - b


def mul(a, b):
    return a * b


def div(a, b):
    return a / b


global_parser = argparse.ArgumentParser(prog="calc")
subparsers = global_parser.add_subparsers(
    title="subcommands", help="arithmetic operations"
)

arg_template = {
    "dest": "operands",
    "type": float,
    "nargs": 2,
    "metavar": "OPERAND",
    "help": "a numeric value",
}

add_parser = subparsers.add_parser("add", help="add two numbers a and b")
add_parser.add_argument(**arg_template)
add_parser.set_defaults(func=add)

sub_parser = subparsers.add_parser("sub", help="subtract two numbers a and b")
sub_parser.add_argument(**arg_template)
sub_parser.set_defaults(func=sub)

mul_parser = subparsers.add_parser("mul", help="multiply two numbers a and b")
mul_parser.add_argument(**arg_template)
mul_parser.set_defaults(func=mul)

div_parser = subparsers.add_parser("div", help="divide two numbers a and b")
div_parser.add_argument(**arg_template)
div_parser.set_defaults(func=div)

args = global_parser.parse_args()

print(args.func(*args.operands))