x = input("Please input expression:") lst = x.split(' ') print(lst) op = lst[1] x = int(lst[0]) y = int(lst[2]) while len(lst) >= 3: if op in ['+','-','*','/']: if op == '+': result = x + y if op == '-': result = x - y if op == '*': result = x * y if op == '/': result = x / y print("The answer is: ",result) for i in range(2): del lst[0] print(lst) op = lst[1] y = int(lst[2]) x = result else: print("operator error")