calculator.py

import argparse
import sys


def _validate(a, b):
    if not isinstance(a, (int, float)) or not isinstance(b, (int, float)):
        raise TypeError("Both arguments must be numeric")


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


def subtract(a, b):
    _validate(a, b)
    return a - b


def multiply(a, b):
    _validate(a, b)
    return a * b


def divide(a, b):
    _validate(a, b)
    if b == 0:
        raise ZeroDivisionError("Cannot divide by zero")
    return a / b


OPERATIONS = {
    "add": add,
    "subtract": subtract,
    "multiply": multiply,
    "divide": divide,
}


def main():
    parser = argparse.ArgumentParser(
        prog="calculator",
        description="A simple CLI calculator",
    )
    parser.add_argument(
        "operation",
        choices=OPERATIONS.keys(),
        help="The operation to perform",
    )
    parser.add_argument("a", type=float, help="First number")
    parser.add_argument("b", type=float, help="Second number")

    args = parser.parse_args()

    try:
        result = OPERATIONS[args.operation](args.a, args.b)
        print(result)
    except ZeroDivisionError as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)
    except TypeError as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)


if __name__ == "__main__":
    main()