Modular Calculator

Build a calculator program organized into separate functions for each arithmetic operation, with proper error handling for invalid input and division by zero.

Requirements

1. Write separate functions: add, subtract, multiply, divide.
2. Each function takes two numbers and returns the result.
3. The divide function must handle division by zero gracefully (return an error message, not crash).
4. Build a menu loop that asks the user to choose an operation and enter two numbers.
5. Validate that user input is numeric using try/except.
6. Allow the user to perform multiple calculations until they choose to exit.

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

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

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

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

def get_number(prompt):
    while True:
        try:
            return float(input(prompt))
        except ValueError:
            print("Invalid input. Please enter a number.")

def main():
    operations = {
        "1": ("Add", add),
        "2": ("Subtract", subtract),
        "3": ("Multiply", multiply),
        "4": ("Divide", divide),
    }

    while True:
        print("\n--- Modular Calculator ---")
        for key, (name, _) in operations.items():
            print(f"{key}. {name}")
        print("5. Exit")

        choice = input("Choose an operation: ")
        if choice == "5":
            print("Goodbye!")
            break

        if choice not in operations:
            print("Invalid option.")
            continue

        name, func = operations[choice]
        a = get_number("Enter first number: ")
        b = get_number("Enter second number: ")
        result = func(a, b)
        print(f"Result: {result}")

if __name__ == "__main__":
    main()

50 XP on completion Back to Day 4

Your Code

def add(a, b):
    # TODO: return a + b
    pass

def subtract(a, b):
    # TODO: return a - b
    pass

def multiply(a, b):
    # TODO: return a * b
    pass

def divide(a, b):
    # TODO: return a / b, handle division by zero
    pass

# Example usage
print(add(5, 3))
print(divide(10, 0))

Output

Click "Run" to execute your code...