python - 为什么我的 Python 代码只添加购物车中最后一件商品的价格？

Question

所以我正在尝试编写一个Python代码，让您将商品添加到购物车中，然后一旦您输入“完成”，它就会将您添加到购物车中的每个商品的价格相加，然后告诉您总价。

我的问题是，一旦我输入“完成”，它只会添加我添加到购物车的最后一个商品的价格，然后将其打印出来。

shopping_cart = [""]

food = shopping_cart

#Stock
stock = {
    "\nFruit\n\n"
    "banana": 50,
    "apple": 15,
    "orange": 32,
    "pear": 15,

    "\nDrinks\n\n"
    "apple juice": 10,
    "orange juice": 10,
    "pinapple juice": 10,
    "milk": 15,

    "\nSnacks\n\n"
    "chips": 20,
    "cookies": 20,
    "chocolate": 25,
    "lollies": 50
}

#Prices 
prices = {
    #Fruit
    "banana": 10,
    "apple": 5,
    "orange": 5,
    "pear": 5,

    #Drinks
    "apple juice": 5,
    "orange juice": 5,
    "pinapple juice": 5,
    "milk": 4.80,

    #Snacks
    "chips": 7,
    "cookies": 4,
    "chocolate": 6,
    "lollies": 5.50
    
}

#Loop
while True:
    item = input("\nEnter an item: ").lower()
    shopping_cart.append(item)

    if item == 'done':
        break

    if item == 'cart':
        print(shopping_cart)

    if item == 'stock':
        for k, v in stock.items():
            print(k + ":", v)


#Define the bill variable
def shopping_bill(food):
    total = 0
    for key in prices:
        for key in stock:
            for item in food:
                if item == key in prices:
                    total += prices[key]
        break 
    print("Your bill total equals $", total)
    print("Thank you for shopping at B&K Supermarket!")

shopping_bill(food)

Answer 1

这里有两个主要问题。第一个是在用户输入购物 list 之前将食物定义为 shopping_cart。因此，它仍然是一个空列表。

要解决此问题，请将 food = shopping_cart 移至 while True 循环之后，如下所示:

while True:
    item = input("\nEnter an item: ").lower()
    shopping_cart.append(item)

    if item == 'done':
        break

    if item == 'cart':
        print(shopping_cart)

    if item == 'stock':
        for k, v in stock.items():
            print(k + ":", v)

food = shopping_cart

第二个问题是您要在字典顶部添加“\nFruit\n\n”和类似的内容。您需要将它们注释掉，这样代码就不会认为它们是字典的一部分。

stock = {
    #fruit
    "banana": 50,
    "apple": 15,
    "orange": 32,
    "pear": 15,

    #drinks
    "apple juice": 10,
    "orange juice": 10,
    "pinapple juice": 10,
    "milk": 15,

    
    "chips": 20,
    "cookies": 20,
    "chocolate": 25,
    "lollies": 50
}

将其输入提示并更改上面的代码

> banana
> apple
> done

产生

Your bill total equals $ 15
Thank you for shopping at B&K Supermarket!