Question

我是python和编码的新手，对于学校项目我必须打印一张简单的收据。我正在使用一些功能，其中一个功能要求购买物品的价格，使用While Not Loop。输入循环，直到用户输入＆＃39; 0＆＃39;。

问题在于，如果我输入带有三位或更多小数位的购买商品价格（例如19.999）。当它们在输入错误后输入0时，Return命令似乎卡在了While Not Loop中。当代码到达Return命令时，执行跳转到While Not循环并再次返回，然后在While Not循环中途跳转到价格= str（价格）＆＃39;并继续正常。结果是我们无法以预期的方式退出程序，使用＆＃39; 0＆＃39;。

这是功能。

def shop_list(): #this definition asks for the prices of the items, adds the input to a list and loops, until 0 is entered, which stops the loop.
    while True:
        try:
            prices = float(input("Please input a value. Enter 0 to print receipt: ")) # the input that allows the customer to enter their prices
            zero_check.append(prices)
            if prices == 0:
                if len(zero_check) == 1:
                    if zero_check[0] == 0:
                        exit_ask()
                    else:
                        'do nothing' #this is a place holder line, something must be here but we dont need anything here
                else:
                    'do nothing'
            else:
                'do nothing'
        except ValueError: #if the input creates an error, do the below
            print("\nERROR, please enter a valid number.\n") #this error message will come up if you input anything other than a number
            continue #loops the back to the 'try'
        else:
            break #breaks the While True loop

    if prices != 0: 
        number = None
        while not number:
            prices = str(prices) #converting the price to a string so we can split it
            string_number = prices.split(".") #splitting the price at the decimal point
            if len(string_number[1]) > 2: #if there is more than two decimal points, print an error
                print ("\nERROR: Too many decimal places!\n")
                prices = float(prices)
                shop_list()
            else:
                number = float(prices)

            prices = str(prices)
            price_lnth = len(prices)

            if price_lnth > 15:
                print ('\nERROR, too many numbers.\n')
                shop_list()
            else:
                prices = float(prices)

            if prices > 0: #if the input was valid then this will run
                shopplist.append(prices) #this is what adds a price into a list
                shop_list() # loops back to the start of this definition              
            elif prices < 0:
                print('\nERROR, no negative numbers.\n')
                shop_list() # loops back to the start of this definition   

    else:
        'do nothing'
    return

Answer 1

当出现错误时（在正常逻辑中），您递归调用backgroundReadFile。然后输入0时，第二次调用返回，但原始的调用继续执行。我建议只使用循环，而不是递归，或者只是递归（但请记住，递归会占用堆栈空间）。

Python，从函数返回失败，陷入While循环

1 个答案: