08_calculator_module.py

# 08_calculator_module.py
# Concept: A math calculator built entirely with functions

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: Division by zero!"
    return a / b

def calculator():
    """Main calculator logic using functions."""
    print("--- Functional Calculator ---")
    print("Select operation: 1.Add, 2.Subtract, 3.Multiply, 4.Divide")
    
    choice = input("Enter choice (1/2/3/4): ")
    
    if choice in ('1', '2', '3', '4'):
        num1 = float(input("Enter first number: "))
        num2 = float(input("Enter second number: "))
        
        if choice == '1':
            print(f"Result: {add(num1, num2)}")
        elif choice == '2':
            print(f"Result: {subtract(num1, num2)}")
        elif choice == '3':
            print(f"Result: {multiply(num1, num2)}")
        elif choice == '4':
            print(f"Result: {divide(num1, num2)}")
    else:
        print("Invalid Input")

# Execute the calculator
if __name__ == "__main__":
    # We use this block to ensure calculator() only runs if the script is executed directly
    calculator()