1.使用以下数据属性和相关方法构建ShoppingCart类。注意：一些方法最初可以是方法存根（空方法），在后面的步骤中完成。

• 注意：我的问题只是我目前陷入的冗长程序的一小部分。程序的其余部分我都做对了，所以它可能看起来不完整。*

1.方法：remove_item()从cart_items列表中删除项。有一个字符串（项的名称）参数。不返回任何内容。如果找不到项名称，则输出以下消息：未找到商品。未删除任何内容。
1.实现print_menu()函数以打印以下选项菜单来操作购物车。
例如：

MENU
a - Add item to cart
r - Remove item from cart
c - Change item quantity
i - Output items' descriptions
o - Output shopping cart
q - Quit

1.实现execute_menu()函数，它有两个参数：一个代表用户选择的字符和一个购物车。execute_menu()根据用户的选择执行下面描述的菜单选项。

class ItemToPurchase:
    def __init__(self):
        self.item_name = 'none'
        self.item_description = 'none'
        self.item_price = 0
        self.item_quantity = 0

    def print_item_cost(self):
        total = self.item_quantity * self.item_price
        print(f'{self.item_name} {self.item_quantity} @ ${self.item_price} = ${total}')
 
   def print_item_description(self):
        print(f'{self.item_name}: {self.item_description}')

class ShoppingCart:
    def __init__(self, customer_name='none', current_date='January 1, 2016'):
        self.customer_name = customer_name
        self.current_date = current_date
        self.cart_items = []

    def remove_item(self, item_name):
        for i in self.cart_items:
            if i.item_name == item_name:
                self.cart_items.remove(i)
            else: 
                print("Item not found in cart. Nothing removed.")

    def get_num_items_in_cart(self):
        total_items = 0
        for i in self.cart_items:
            total_items += i.item_quantity
        return total_items
    
    def get_cost_of_cart(self):
        total_cost = 0
        for i in self.cart_items:
            total_cost += i.item_price * i.item_quantity
        return total_cost
        
    def print_total(self):
        print(f'{self.customer_name}\'s Shopping Cart - {self.current_date}')
        print(f'Number of Items: {self.get_num_items_in_cart()}\n')
        
        if len(self.cart_items) > 0:
            for i in self.cart_items:
                i.print_item_cost()
        else:
            print('SHOPPING CART IS EMPTY')
        print(f'\nTotal: ${self.get_cost_of_cart()}')
    
    def print_description(self):
        print(f'{self.customer_name}\'s Shopping Cart - {self.current_date}\n')

        print('Item Descriptions')
        if len(self.cart_items) > 0:
            for i in self.cart_items:
                i.print_item_description()
        else:
            print('SHOPPING CART IS EMPTY')

def print_menu():
    print('MENU')
    print('a - Add item to cart')
    print('r - Remove item from cart')
    print('c - Change item quantity')
    print('i - Output items\' descriptions')
    print('o - Output shopping cart')
    print('q - Quit')
    print()

def execute_menu(choice, cart):
    if choice == 'r':
        print('REMOVE ITEM FROM CART')
        item = input('Enter name of item to remove:\n')
        cart.remove_item(item)
        print()

if __name__ == "__main__":
    menu_choice = ' '
    customer_name = input('Enter customer\'s name:\n')
    date = input('Enter today\'s date:\n')
    
    print(f'\nCustomer name: {customer_name}')
    print(f'Today\'s date: {date}')
    print()
    
    my_cart = ShoppingCart(customer_name, date)
    
    print_menu()
    
    while menu_choice != 'q':
        menu_choice = input('Choose an option:\n')
        if menu_choice in ['a', 'r', 'c', 'i', 'o']:
            execute_menu(menu_choice, my_cart)
            print_menu()

输入为：

John Doe 
February 1, 2016 
a 
Nike Romaleos 
Volt color, Weightlifting shoes 
189 
2 
a 
Chocolate Chips 
Semi-sweet 
3 
5 
a 
Powerbeats 2 Headphones 
Bluetooth headphones 
128 
1 
r   
Chocolate Chips 
o   
q

我的输出为：

REMOVE ITEM FROM CART
Enter name of item to remove:
***Item not found in cart. Nothing removed.***

MENU
a - Add item to cart
r - Remove item from cart
c - Change item quantity
i - Output items' descriptions
o - Output shopping cart
q - Quit

Choose an option:
OUTPUT SHOPPING CART
John Doe's Shopping Cart - February 1, 2016
Number of Items: 3

Nike Romaleos 2 @ $189 = $378
Powerbeats 2 Headphones 1 @ $128 = $128

Total: $506

MENU
a - Add item to cart
r - Remove item from cart
c - Change item quantity
i - Output items' descriptions
o - Output shopping cart
q - Quit

Choose an option:

实际输出应为：

REMOVE ITEM FROM CART
Enter name of item to remove:

MENU
a - Add item to cart
r - Remove item from cart
c - Change item quantity
i - Output items' descriptions
o - Output shopping cart
q - Quit

Choose an option:
OUTPUT SHOPPING CART
John Doe's Shopping Cart - February 1, 2016
Number of Items: 3

Nike Romaleos 2 @ $189 = $378
Powerbeats 2 Headphones 1 @ $128 = $128

Total: $506

MENU
a - Add item to cart
r - Remove item from cart
c - Change item quantity
i - Output items' descriptions
o - Output shopping cart
q - Quit

Choose an option: