A calculator with operations add, subtract, multiplication and division.

def calculator(num1, num2, operation):
  if operation == "add":
    return num1 + num2
  elif operation == "subtract":
    return num1 - num2
  elif operation == "multiply":
    return num1 * num2
  elif operation == "divide":
    return num1 / num2
  else:
    return "Operation invalid"
    
calculator(1, 2, "add")