python - 对Python中的AttributeError感到困惑

Question

我正在尝试做以下项目:

想象一下，您已经开了一家小餐馆，并试图使其更容易接受和计算订单。由于您的餐厅仅出售9种不同的商品，因此您将每个商品分配给一个数字，如下所示。

Chicken Strips - $3.50
French Fries - $2.50
Hamburger - $4.00
Hotdog - $3.50
Large Drink - $1.75
Medium Drink - $1.50
Milk Shake - $2.25
Salad - $3.75
Small Drink - $1.25

为了快速接受订单，您的程序应允许用户键入数字字符串，然后应计算订单成本。例如，如果订购了一大杯饮料，两杯小饮料，两个汉堡包，一个热狗和一份沙拉，则用户应键入5993348，程序应说费用为$ 19.50。另外，请确保程序循环运行，以便用户可以接受多个订单，而不必每次都重新启动程序。

到目前为止，我的代码如下:

print "------------------Menu-------------------"

class Menu_Item():
    def __init__(self, num,item,price):
        self.num = num
        self.item = item
        self.price = price
    def __repr__(self):
        return "\n" + str(self.num) + ".  " + self.item + " - $" + str(self.price) + ' dollars'



Strips = Menu_Item(1,'Chicken Strips', 3.50)
Fries = Menu_Item(2,"Fries",2.50)
Burger = Menu_Item(3,"Burger",4.00)
Hotdog = Menu_Item(4,"Hotdog",3.50)
Large_Drink = Menu_Item(5,"Large Drink",1.75)
Medium_Drink = Menu_Item(6,"Medium Drink", 1.50)
Milkshake = Menu_Item(7,"Milkshake", 2.25)
Salad = Menu_Item(8,"Salad", 3.75)
Small_Drink = Menu_Item(9,"Small Drink", 1.25)


Class_Items = [Strips,Fries,Burger,Hotdog,Large_Drink,Medium_Drink,Milkshake,Salad,Small_Drink]


print Class_Items

def take_order():
    count = 0
    string = raw_input("Enter your order")
    order = []
    for a in string:
        order.append(a)
    for food in Class_Items:
        for b in order:
            if b == Menu_Item.num:
                count = count + Menu_Item.price
                return count
            else:
                print "-"

take_order()

我收到以下错误。我已经尝试了很多方法来实现此目的，但我不知道为什么编译器无法识别num属性。关于为什么发生这种情况有什么建议吗？谢谢!

Traceback (most recent call last):
  File "python", line 43, in <module>
  File "python", line 37, in take_order
AttributeError: class Menu_Item has no attribute 'num'

Answer 1

您为什么在这里访问Menu_Item？那是类(class)本身；您从列表中获得的项目称为food。