# 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, "+"...