我有一个Python介绍类，其中部分说明是：
(2) 使用以下数据属性和相关方法构建 ShoppingCart 类。注意：有些最初可以是方法存根（空方法），将在后面的步骤中完成。
添加_项目（）
将商品添加到 cart_items 列表。有参数 ItemToPurchase。不返回任何东西。
代码是：
class ItemToPurchase:
def __init__(self):
self._name = "none"
self._price = 0
self._quantity = 0
self._description = "none"
def item_name(self, name):
self._name = name
def item_price(self, price):
self._price = price
def item_quantity(self, quantity):
self._quantity = quantity
def item_description(self, description):
self._description = description
def __str__(self):
print("For item " + self._name + ": " + self._description + " there are " + str(self._quantity) + " available at $" + str(self._price) + ".")
def print_item_cost(self):
print(self._name + " " + str(self._quantity) + " @ $" + str(self._price) + " = $" + str(self._quantity * self._price))
def print_item_description(self):
print(self._name + ": " + self._description)
class ShoppingCart:
def __init__(self, name="none", date="January 1, 2016"):
cart_items = []
_customer_name = name
_current_date = date
def add_item(self, cartItem):
self.cart_items.append(cartItem)
def remove_item(self, item_name):
count = 0
itms = self.cart_items[:]
for i in range(len(itms)):
itm = itms[i]
if itm._name == item_name:
del self.cart_items[i]
count += 1
if count == 0:
print(" ")
print("Item not found in cart. Nothing removed.")
def modify_item(self, ItemToPurchase):
count = 0
itms = self.cart_items[:]
for i in range(len(itms)):
itm = itms[i]
if itm._name == ItemToPurchase._name:
count += 1
if ItemToPurchase._description != "none":
itm.item_description(ItemToPurchase._description)
if ItemToPurchase._price != 0:
itm.item_price(ItemToPurchase._price)
if ItemToPurchase._quantity != 0:
itm.item_quantity(ItemToPurchase._quantity)
if count == 0:
print(" ")
print("Item not found in cart. Nothing modified.")
def get_num_items_in_cart(self):
count = 0
itms = self.cart_items[:]
for i in range(len(itms)):
itm = itms[i]
count += itm._quantity
return count
def get_cost_of_cart(self):
cost = 0
itms = self.cart_items[:]
for i in range(len(itms)):
itm = itms[i]
cost += (itm._quantity * itm._price)
return cost
def print_total(self):
print(self._customer_name + "'s Shopping Cart - " + self._current_date)
count = len(self.cart_items)
if count == 0:
print(" ")
print("SHOPPING CART IS EMPTY")
return 0
print("Number of Items: " + str(count))
print(" ")
for itm in self.cart_items:
itm.print_item_cost()
total = self.get_cost_of_cart()
print("Total: $" + str(total))
def print_descriptions(self):
print(self._customer_name + "'s Shopping Cart - " + self._current_date)
print(" ")
print("Item Descriptions")
for itm in self.cart_itmes:
print(itm.item_name() + ": " + itm.item_description())
def print_menu(cart):
print(" ")
print("MENU")
print("a - Add item to cart")
print("r - Remove item from cart")
print("c - Change item quntity")
print("i - Output items' descriptions")
print("o - Output shopping cart")
print("q - Quit")
print(" ")
def main():
#Define Constants and variables
custName = ""
dateToday = ""
custName = input("Enter customer's name: ")
dateToday = input("Enter today's date: ")
print("Customer name: " + custName)
print("Today's date: " + dateToday)
myCart = ShoppingCart(custName,dateToday)
option = ""
while option != "q":
print_menu(myCart)
option = input("Choose an option: ").lower().strip()
if option == "o":
myCart.print_descriptions()
elif option == "a":
print("ADD ITEM TO CART")
itemName = input("Enter the item name: ")
itemDescr = input("Enter the item description: ")
itemPrice = int(input("Enter the item price: "))
itemQuantity = int(input("Enter the item quantity: "))
print(" ")
cartItem = ItemToPurchase()
cartItem.item_name(itemName)
cartItem.item_description(itemDescr)
cartItem.item_price(itemPrice)
cartItem.item_quantity(itemQuantity)
myCart.add_item(cartItem)
elif option == "r":
print("REMOVE ITEM FROM CART")
itemName = input("Enter name of item to remove: ")
myCart.remove_item(itemName)
elif option == "c":
print("CHANGE ITEM QUNATITY")
itemName = input("Enter the item name: ")
itemQuantity = int(input("Enter the new quantity: "))
changeItem = ItemToPurchase(itemName)
changeItem.item_quantity(itemQuantity)
myCart.modify_item(changeItem)
main()
我收到以下错误：
Enter customer's name: Rog
Enter today's date: Oct 20
Customer name: Rog
Today's date: Oct 20
MENU
a - Add item to cart
r - Remove item from cart
c - Change item quntity
i - Output items' descriptions
o - Output shopping cart
q - Quit
Choose an option: a
ADD ITEM TO CART
Enter the item name: Sketchers
Enter the item description: Black
Enter the item price: 120
Enter the item quantity: 2
回溯（最近一次调用最后一次）：文件 “C：\ PythonWorkspace \ Chapter9Assignment \ src \ onlineShoppingCart2.py”， 第 176 行，在 main() 文件“C:\PythonWorkspace\Chapter9Assignment\src\onlineShoppingCart2.py”, 第 163 行，主要 myCart.add_item(cartItem) 文件“C:\PythonWorkspace\Chapter9Assignment\src\onlineShoppingCart2.py”, 第 44 行，在 add_item 中 self.cart_items.append(cartItem) AttributeError: 'ShoppingCart' 对象没有属性 'cart_items'
谁能告诉我我做错了什么？
class ShoppingCart:
def __init__(self, name="none", date="January 1, 2016"):
cart_items = []
_customer_name = name
_current_date = date
这些都是局部变量。如果您希望它们成为实例的属性，则必须显式引用
selfclass ShoppingCart:
def __init__(self, name="none", date="January 1, 2016"):
self.cart_items = []
self._customer_name = name
self._current_date = date
This should give 29/29 points (Python)
class ItemToPurchase:
def __init__(self,
item_name="none",
item_price=0,
item_quantity=0,
item_description="none"):
self.item_name = item_name
self.item_price = item_price
self.item_quantity = item_quantity
self.item_description = item_description
# prints out the item cost
def print_item_cost(self):
self.item_price = int(self.item_price)
self.item_quantity = int(self.item_quantity)
return f'{self.item_name} {self.item_quantity} @ ${self.item_price} = ${self.item_price*self.item_quantity}'
# prints item_description attribute for an itemToPurchase object
def print_item_description(self):
return f'{self.item_name}: {self.item_description}'
class ShoppingCart(ItemToPurchase):
def __init__(self, customer_name, current_date):
ItemToPurchase.__init__(self)
self.customer_name = customer_name
self.current_date = current_date
self.cart_items = []
# adds an item to cart_items
def add_item(self, obj):
self.cart_items.append(obj)
# remove items from the cart
def remove_item(self, item):
count = 0
for i in range(len(self.cart_items) - 1):
if self.cart_items[i].item_name == item:
self.cart_items.pop(i)
count += 1
break
if count == 0:
print("Item not found in cart. Nothing removed.")
# modify item in cart by the name
def modify_item(self, obj):
for cart_item in self.cart_items:
if cart_item.item_name == obj.item_name:
cart_item.item_quantity = obj.item_quantity
else:
print("Item not found in cart. Nothing modified.")
# returns the number of item in the list
def get_num_items_in_cart(self):
total_quantity = 0
for x in self.cart_items:
self.item_quantity = int(x.item_quantity)
total_quantity += self.item_quantity
return total_quantity
# returns the total cost of items
def get_cost_of_cart(self):
cart_cost = 0
for i in self.cart_items:
self.item_price = int(i.item_price)
self.item_quantity = int(i.item_quantity)
cost = self.item_price * self.item_quantity
cart_cost += cost
return cart_cost
# outputs total objects in cart
def print_total(self):
if len(self.cart_items) == 0:
print(f'{self.customer_name}\'s Shopping Cart - {self.current_date}')
print(f'Number of Items: {self.get_num_items_in_cart()}\n')
print("SHOPPING CART IS EMPTY\n")
print(f'Total: ${self.get_cost_of_cart()}')
else:
print(f'{self.customer_name}\'s Shopping Cart - {self.current_date}')
print(f'Number of Items: {self.get_num_items_in_cart()}\n')
for item in self.cart_items:
print(item.print_item_cost())
print()
print(f'Total: ${self.get_cost_of_cart()}')
# outputs the name of the item and description
def print_descriptions(self):
print(f'{self.customer_name}\'s Shopping Cart - {self.current_date}')
print()
print("Item Descriptions")
for item in self.cart_items:
print(item.print_item_description())
# menu
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")
# excute menu
def execute_menu(char, cart):
if char == "a":
print("ADD ITEM TO CART")
item_name = input("Enter the item name:\n")
item_desc = input("Enter the item description:\n")
item_price = input("Enter the item price:\n")
item_quantity = input("Enter the item quantity:\n")
item = ItemToPurchase(item_name, item_price, item_quantity, item_desc)
cart.add_item(item)
elif char == "r":
print("REMOVE ITEM FROM CART")
rmv_item = input("Enter name of item to remove:\n")
cart.remove_item(rmv_item)
elif char == "c":
print("CHANGE ITEM QUANTITY")
item_name = input("Enter the item name:\n")
new_qunatity = input("Enter the new quantity:\n")
new_obj = ItemToPurchase(item_name, sc.item_price, new_qunatity,
sc.item_description)
cart.modify_item(new_obj)
elif char == "i":
print("OUTPUT ITEMS' DESCRIPTIONS")
cart.print_descriptions()
elif char == "o":
print("OUTPUT SHOPPING CART")
cart.print_total()
if __name__ == "__main__":
choice = ""
options = ["a", "r", "c", "i", "o", "q"]
# parameters for ShoppingCart
custo_name = input("Enter customer's name:\n")
today_date = input("Enter today's date:\n")
print()
sc = ShoppingCart(custo_name, today_date)
print(f'Customer name: {sc.customer_name}')
print(f"Today's date: {sc.current_date}\n")
print_menu()
print()
# while loop that prints the menu until user enters q - quit
while True:
choice = input("Choose an option:\n")
if choice == "q":
break
else:
if choice in options:
execute_menu(choice, sc)
print()
print_menu()
print()
else:
choice = input("Choose an option:\n")
我一直在研究这个实验室的第一部分，我想分享它，以防人们发现它有帮助：P 我知道我对一些价值观的命名很糟糕，但是嘿，你能做什么，我觉得这很有趣
class ItemToPurchase:
def __init__(self, name = "none", price = 0, quantity= 0, description= "none"):
self.item_name = name
self.item_price = price
self.item_quantity = quantity
self.item_description = description
def __str__(self):
print(f"For item {self.item_name}: {self.item_description} there are {self.item_quantity} available at $ {self.item_price}.")
def print_item_cost(self):
print(f'{self.item_name} {self.item_quantity} @ ${self.item_price} = ${self.item_price * self.item_quantity}')
def print_item_description(self):
print(f'{self.item_name}: {self.item_description}')
您可以看到我的 ItemToPurchase init 方法与第一篇文章有何不同，但与 14 :3 相比，我在 5 行中定义了所有术语（我知道我在吹牛，而我的打印部分看起来像一个粗略的战争草图和平，但是这门课是我第一次编码，所以让我休息一下吧）
if name == "main":
test= ItemToPurchase()
print('Item 1')
test.item_name = input("Enter the item name:")
print()
test.item_price= int(input("Enter the item price:"))
print()
test.item_quantity = int(input("Enter the item quantity:"))
print()
lame= ItemToPurchase()
print()
print('Item 2')
lame.item_name = input("Enter the item name:")
print()
lame.item_price= int(input("Enter the item price:"))
print()
lame.item_quantity = int(input("Enter the item quantity:"))
print()
print()
print('TOTAL COST')
test.print_item_cost()
lame.print_item_cost()
print()
print(f'Total: ${lame.item_price * lame.item_quantity + test.item_price * test.item_quantity}')