购物车数量不更新

Question

我有一个基本的购物车。我以为它在工作，但后来我发现即使它运行无误，它也没有做我认为应该做的事情，我在解决问题时遇到了麻烦。

如果我第二次实例化一个项目，像这样：

    item1 = Item(1, "Cucumbers", 1., 1, 'kg')
    item2 = Item(2, "Tissues", 2., 2, 'dozen')
    item3 = Item(3, "Tomatoes", 3., 5, 'pound')
    # item4 = Item(4, "Toothpaste", 1., 5, 'box')
    item4 = Item(4, "Cucumbers", 1., 2, 'kg')

我想要的是将项目 1 中的黄瓜数量增加到“3” 并自动删除第 4 项。

我认为这符合我的预期，但事实并非如此：

            elif k == 'name':
                total_qty = v.qty + item.qty
                if total_qty:
                    v.qty = total_qty
                    continue
                self.remove_item(k)
            else:
                v[k] = item[k]

代码运行没有错误，但我最终得到了两个独立的黄瓜实例。

完整代码：

class Item(object):
    def __init__(self, unq_id, name, price, qty, measure):
        self.unq_id = unq_id
        self.product_name = name
        self.price = price
        self.qty = qty
        self.measure = measure


class Cart(object):
    def __init__(self):
        self.content = dict()

    def __format__(self, format_type):
        if format_type == 'short':
            return ', '.join(item.product_name for item in self.content.values())

        elif format_type == 'long':
            return '\n'.join(f'\t\t{item.qty:2} {item.measure:7} {item.product_name:12} @ '
                             f'${item.price:1.2f} ... ${item.qty * item.price:1.2f}'
                             for item in self.content.values())

    def add(self, item):
        if item.unq_id not in self.content:
            self.content.update({item.unq_id: item})
            return
        for k, v in self.content.get(item.unq_id).items():
            if k == 'unq_id':
                continue
            elif k == 'name':
                total_qty = v.qty + item.qty
                if total_qty:
                    v.qty = total_qty
                    continue
                self.remove_item(k)
            else:
                v[k] = item[k]

    def get_total(self):
        return sum([v.price * v.qty for _, v in self.content.items()])

    def get_num_items(self):
        return sum([v.qty for _, v in self.content.items()])

    def remove_item(self, key):
        self.content.pop(key)


if __name__ == '__main__':
    item1 = Item(1, "Cucumbers", 1., 1, 'kg')
    item2 = Item(2, "Tissues", 2., 2, 'dozen')
    item3 = Item(3, "Tomatoes", 3., 5, 'pound')
    # item4 = Item(4, "Toothpaste", 1., 5, 'box')
    item4 = Item(4, "Cucumbers", 1., 2, 'kg')
    cart = Cart()
    cart.add(item1)
    cart.add(item2)
    cart.add(item3)
    cart.add(item4)
    print("Your cart contains: {0:short}".format(cart))
    # cart.remove_item(1)
    print()
    print("Your cart contains: \n {0:long}".format(cart))
    print()
    print("The total number of items in your cart is: ", cart.get_num_items())
    print()
    print("The total cost of the items in your cart is: ", cart.get_total())
    print()
    cart.remove_item(3)
    print("Your cart contains: {0:short}".format(cart))
    print()
    print("Your cart contains: \n {0:long}".format(cart))
    print()
    print("The total number of items in your cart is: ", cart.get_num_items())
    print()
    print("The total cost of the items in your cart is: ", cart.get_total())

Answer 1

修复方法是：

def add(self, item):
    if item.unq_id not in self.content:
        self.content.update({item.unq_id: item})
        return
    else:
        self.content[item.unq_id].qty = self.content[item.unq_id].qty + item.qty

购物车数量不更新

Shopping cart quantity not updating

python-3.6