Example: Simple Calculator by Using Functions
# This function adds two numbers def add(x, y): return x + y # This function subtracts two numbers def subtract(x, y): return x - y # This function multiplies two numbers def multiply(x, y): return x * y # This function divides two numbers def divide(x, y): return x / y print("Select operation.") print("1.Add") print("2.Subtract") print("3.Multiply") print("4.Divide") while True: # take input from the user choice = input("Enter choice(1/2/3/4): ") # check if choice is one of the four options if choice in ('1', '2', '3', '4'): try: num1 = float(input("Enter first number: ")) num2 = float(input("Enter second number: ")) except ValueError: print("Invalid input. Please enter a number.") continue if choice == '1': print(num1, "+", num2, "=", add(num1, num2)) elif choice == '2': print(num1, "-", num2, "=", subtract(num1, num2)) elif choice == '3': print(num1, "*", num2, "=", multiply(num1, num2)) elif choice == '4': print(num1, "/", num2, "=", divide(num1, num2)) # check if user wants another calculation # break the while loop if answer is no next_calculation = input("Let's do next calculation? (yes/no): ") if next_calculation == "no": break else: print("Invalid Input") Output
Select operation. 1.Add 2.Subtract 3.Multiply 4.Divide Enter choice(1/2/3/4): 3 Enter first number: 15 Enter second number: 14 15.0 * 14.0 = 210.0 Let's do next calculation? (yes/no): no
In this program, we ask the user to choose an operation. Options 1, 2, 3, and 4 are valid. If any other input is given, Invalid Input is displayed and the loop continues until a valid option is selected.
Two numbers are taken and an if...elif...else branching is used to execute a particular section. User-defined functions add(), subtract(), multiply() and divide() evaluate respective operations and display the output.
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