Python中的類和對象

Question

我正在運行一個簡單的在線購物車程序，當我試圖運行它時，最終結果爲空。我理解關於類和對象的概念，但我真的需要幫助。它應該是這樣的：

Item 1 
Enter the item name: Chocolate Chips 
Enter the item price: 3 
Enter the item quantity: 1 

Item 2 
Enter the item name: Bottled Water 
Enter the item price: 1 
Enter the item quantity: 10 

TOTAL COST 
Chocolate Chips 1 @ $3 = $3 
Bottled Water 10 @ $1 = $10 

Total: $13 

這裏是我到目前爲止寫的，：

class ItemsToPurchase : 

    def __init__(self, item_name = "none", item_price = 0, item_quantity = 0): 
     self.item_name = item_name 
     self.item_price = item_price 
     self.item_quantity = item_quantity 

    def print_item_cost(self): 
     total = item_quantity * item_price 
     print('%s %d @ $%f = $%f' % (item_name, item_quantity, item_price, total)) 

def main(): 

    print('Item 1') 
    print() 

    item_name = str(input('Enter the item name: ')) 
    item_price = float(input('Enter the item price: ')) 
    item_quantity = int(input('Enter the item quantity: ')) 

    item_one = ItemsToPurchase(item_name, item_price, item_quantity) 
    item_one.print_item_cost() 

    print('Item 2') 
    print() 

    item_name = str(input('Enter the item name: ')) 
    item_price = float(input('Enter the item price: ')) 
    item_quantity = int(input('Enter the item quantity: ')) 

    item_two = ItemsToPurchase(item_name, item_price, item_quantity) 
    item_two.print_item_cost() 

    print('TOTAL COST') 
    item_one.print_item_cost() 
    item_two.print_item_cost() 

if __name__ == "__main__": 
    main() 

我做了什麼錯？

Answer 1

您的print_item_cost方法有些問題，它應該是這樣的：

def print_item_cost(self): 
    total = self.item_quantity * self.item_price 
    print('%s %d @ $%f = $%f' % (self.item_name, self.item_quantity, self.item_price, total)) 

你指的是類屬性是這樣的：如果self.attr