代码之家 › 专栏 › 技术社区 › vkk07

嵌套dict python中的购物车总价

python-3.x python

vkk07 · 技术社区 · 6 年前

我想用下面的代码计算我的购物车中的总价,但是我不能重复我的项目dict中的价格。这里缺少一些东西。另外,如果for循环是固定的,那么有没有什么方法可以使用理解进行迭代?

class ShoppingCart(object):
    def __init__(self):
        self.item = None
        self.quantity = None
        self.price = None
        self.items = {}
    def add(self, item, price, quantity):

        if item in self.items:
            previous_quantity = self.items[item]['quantity']
            previous_price = self.items[item]['price']

            self.items[item] = {'quantity': previous_quantity +   quantity,
                                'price': previous_price + price}
        else:
            self.items[item] = {'quantity':quantity,
                           'price':price}

    def total_items_in_cart(self):
         print(len(self.items))

    def total_items_price_in_cart(self):
         print(sum([price
                 for price in self.items.values()]))

sc = ShoppingCart()
sc.add('book', 30, 1)
# sc.add('book', 132, 1)

sc.add('toothbrush', 4, 10)
# sc.add('toothbrush', 5, 20)

# sc.total_items_in_cart()

cart_price_total = []
for item, value in sc.items.items():
    print("\n{}".format(item))
    for price,qty in value.items():
        print("{} :{}".format(price, qty))
        cart_price_total.append(qty)

print(cart_price_total) # this does not print what I want...

有没有一种方法可以使用理解来获取我的购物车中的总价值?

编辑:

I added the data using a tuple, and it seems simple now. Cannot figure out why...

class ShoppingCart(object):
    def __init__(self):
        self.item = None
        self.quantity = None
        self.price = None
        self.items = {}
    def add(self, item, price, quantity):
        if item in self.items:
            previous_quantity = self.items[item]['quantity']
            previous_price = self.items[item]['price']
            self.items[item] = (previous_quantity+quantity, previous_price+price)
        else:
            self.items[item] = (price, quantity)

    def total_items_in_cart(self):
         return(len(self.items))

    def total_items_price_in_cart(self):
         return(sum([price
                 for price, quantity in self.items.values()]))

sc = ShoppingCart()
sc.add('book', 30, 1)
sc.add('toothbrush', 4, 10)
print(sc.total_items_in_cart())
print(sc.total_items_price_in_cart())

3 回复 | 直到 6 年前

AGN Gazer 6 年前

我只需要定义一个新的实例变量,例如 _total_price 并在添加项目时保持更新:

class ShoppingCart(object):
    def __init__(self):
        self.item = None
        self.quantity = None
        self.price = None
        self.items = {}
        self._total_price = 0

    def add(self, item, price, quantity):
        if item in self.items:
            previous_quantity = self.items[item]['quantity']
            previous_price = self.items[item]['price']
            self.items[item] = {'quantity': previous_quantity + quantity,
                                'price': previous_price + price}
        else:
            self.items[item] = {'quantity':quantity, 'price':price}
        self._total_price += price * quantity

    @property
    def total_items_in_cart(self):
        return len(self.items) # better return a value instead of printing it

    @property
    def total_items_price_in_cart(self):
        return self._total_price

sc = ShoppingCart()
sc.add('book', 30, 1)
# sc.add('book', 132, 1)

sc.add('toothbrush', 4, 10)
# sc.add('toothbrush', 5, 20)

print(sc.total_items_in_cart)
print(sc.total_items_price_in_cart)

当然,当用户想要从购物车中删除商品时,您需要处理这个案例。

Ivan Vinogradov 6 年前

改变你的 total_items_price_in_cart 功能:

def total_items_price_in_cart(self):
    items_prices = {k: v['price'] * v['quantity'] for (k, v) in self.items.items()}
    # items_prices == {'book': 30, 'toothbrush': 40}
    return sum(items_prices.values())

有问题的输入数据的输出:

70

Ivan Vinogradov 6 年前

你的 ShoppingCart 类具有price属性,但您不使用它。你应该只使用你的 self.items = {} ,您不使用 self.item , self.quantity 和 self.price .

print(cart_price_total) # this does not print what I want...

是的,但似乎您的购物车价格总和不考虑您的物品价值…但价值和项目是有价值的。

试试这个:

print(sum([sc.items[x]['price']*sc.items[x]['quantity'] for x in sc.items]))