Question

我在2.7中有一个工作货币转换器，但我想确保程序没有得到用户无法处理的数据。

如何让用户输入被理解为与案例无关
如果用户输入错误，如何让程序重启;即使是休息，但我无法解决如何做到这一点，尽管搜索并测试一些方法。

我已经离开了剩下的代码，因为使用预设数字有效地复制了第一组乘法。

currency = str(raw_input ("""what currency would you like to covert: GBP, EURO, USD OR YEN?
"""))
exchange = str(raw_input("""what currency would you like in exchange? : GBP, EURO, USD OR YEN?
                              """))
amount = int(input("""how much would you like to convert?
                      """))
decision = str(raw_input("""Please enter u for user input exchange rate or s for the preset exchange rate
"""))

if decision == "u" :
    user_rate = raw_input("Please enter the current exchange rate")
    exchange_value = int(amount) *  int(user_rate)
    print ("At the user found exchange rate you will receive",exchange_value,exchange)

elif decision == "s" :
    if currency  == "GBP" and exchange == "USD":
        exchange_value= int(amount) * 1.6048
        print ("At the preset exchange rate you will receive",exchange_value,exchange)

    if currency  == "GBP" and exchange == "EUR":
        exchange_value= int(amount) * 1.2399
        print ("At the preset exchange rate you will receive",exchange_value,exchange)

Answer 1

1）无论

，您都可以使用相同的大小写比较用户输入字符串

if currency.lower() == 'gbp'

或

if currency.upper() == 'GBP'

2）您可以在while循环中运行程序，这样如果不满足条件，您可以continue到循环的下一次迭代（这将从头开始重新启动程序）

while True:
  # get user input
  # validate user input
  # if input not valid continue, which will "restart" your program

Answer 2

这样的事情会帮助你开始

    valid_input = ('EUR', 'GBP', 'USD', 'JPY')

    while True:
        # Obtain user data

        # Make sure all its in caps
        currency = currency.upper()
        exchange = exchange.upper()

        if currency in valid_input and exchange in valid_input:
            break 

         print ("Error Invalid input, try again...")

    # Proccess data...

如何使用break语句

2 个答案: