Python 3.x 在实例变量中查找最低值

我试图返回购物车中最便宜的商品，但是，我无法以任何方式访问价目表

使用和

class Item:

    """ An instance of an item """
    def __init__(self, price):
        """ (Item, float)
        Initialize an Item
        """
        self.price = price

---

请发布两个类的完整代码。我不会在这里返回-1。。如果购物车中没有任何物品，最便宜的物品是0。我也不会，但这是原始问题中方法的描述所说的。如果有人输入物品价格为-1，那会很有趣…：但是是的-这是OP所说的：p

class Item:

    """ An instance of an item """
    def __init__(self, price):
        """ (Item, float)
        Initialize an Item
        """
        self.price = price

def show_cheapest_item(self):
    """ (ShoppingCart) -> int
    Return the cheapest item in the cart, or -1 if no items are in the cart
    """
    if len(self.cart) == 0:
        return -1
    cheapest_item = self.cart[0]
    for item in self.cart[1:]:
        if item.price < cheapest_item.price:
            cheapest_item = item
    return cheapest_item

class ShoppingCart:

    def __init__(self):
        self.cart = []

    def add_item(self, item):
       """ (ShoppingCart, Item) -> NoneType
       Adds an item to the cart.
       """
       self.cart.append(item)

    def show_cheapest_item(self):
       """ (ShoppingCart) -> int
       Return the cheapest item in the cart, or -1 if no items are in the cart
       """
       return -1 if len(self.cart) == 0 else min(self.cart)

import operator

def show_cheapest_item(self):
    """ (ShoppingCart) -> int
    Return the cheapest item in the cart, or -1 if no items are in the cart
    """
    return -1 if not self.cart else min(self.cart, key=operator.attrgetter('price'))