中断和传递功能未正确处理

Question

函数break和pass似乎在正确的输入下不会起作用，程序会停止，而在没有正确输入的情况下，程序决定不中断而是打印字符串，告诉用户有问题并继续运行。

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?

                      """))

valid_input = ('EUR','eur','GBP','gbp' ,'USD','usd','JPY','jpy')

while True:

    if currency in valid_input and exchange in valid_input:

        pass

    else:

        print("incorrect input, please restart program")

        break

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

“中断”仅在insinde开关中有效，并且持续/