python - 除了 ValueError 在我的代码中不起作用我不知道为什么

Question

我包含了 ValueError 以确保用户输入一个整数，但它声明未绑定(bind)的本地错误并声明该变量在赋值之前被引用

def bagTotal():
    while True:
        try:
            bagCount = int(input("Now we just need the number of bags you wish to take with you: "))          
        except ValueError:
            print("Please input a number")
            print("")
        if (bagCount <= 2):
            print("As stated before the first bag is free")
            print(name,",your total is","$%>2F"%ticket)
            print("")
            print("")
            restart()
        else:
            bagTotal = (bagCount - 1) * bagFee
            ticketTotal = bagTotal + ticketamount
            print(name,", your new total is","$%.2f"%ticketTotal)
            print("")
            print("")
            restart()

Answer 1

如果您遇到 ValueError，程序将继续运行您的 if 语句等，然后再进入 while 循环的下一个循环。如果您没有收到错误，您只希望该代码运行，因此您的代码应如下所示:

def bagTotal():
    while True:
        try:
            bagCount = int(input("Now we just need the number of bags you wish to take with you: "))
            if (bagCount <= 2):
                print("As stated before the first bag is free")
                print(name,",your total is","$%>2F"%ticket)
                print("")
                print("")
                restart()
            else:
                bagTotal = (bagCount - 1) * bagFee
                ticketTotal = bagTotal + ticketamount
                print(name,", your new total is","$%.2f"%ticketTotal)
                print("")
                print("")
                restart()          
        except ValueError:
            print("Please input a number")
            print("")