python - 如何阻止用户输入无效的操作标志

Question

如何强制用户在我的计算器上输入+、-或*？/

我的计算器目前可以工作，但我想阻止用户在操作字段上输入 int 字符串。

while True:
    number1 = input("Enter First Number! ")
    try:
        number1 = float(number1)
        break
    except ValueError:
        print("Enter a number")

Operation = input("Enter Operation! ")

while True:
    number2 = input("Enter Second Number! ")
    try:
        number2 = float(number2)
        break
    except ValueError:
        print("Enter a Number")

if Operation == "+":
    result = float(number1) + float(number2)
    print(result)

elif Operation =="-":
    result = float(number1) - float(number2)
    print(result)

elif Operation == "*":
    result = float(number1) * float(number2)
    print(result)

elif Operation == "/":
    result = float(number1) / float(number2)
    print(result)

else:
    print("Incorrect Operation")

标签： pythonif-statementwhile-loopcalculator