以下编辑！
这是我的retail_item课程：
#RetailItem Class
class RetailItem:
def __init__(self, desc, inventory, price):
self.__desc=desc
self.__inventory=inventory
self.__price=price
#mutators
def set_desc (self, desc):
self.__desc=desc
def set_inventory (self, inventory):
self.__inventory=inventory
def set_price (self, price):
self.__price = price
#accessors
def get_desc(self):
return self.__desc
def get_inventory(self):
return self.__inventory
def get_price(self):
return self.__price
def __str__(self):
return 'Item Description:' + self.__desc, \
'\tNumber of Units:' + self.__inventory, \
'\tPrice: $' + self.__price
我的cash_register课程：
#CashRegister Class
class CashRegister:
def __init__(self, purchase, total, show, clear):
self.__purchase=purchase
self.__total=total
self.__show=show
self.__clear=clear
#mutators
def purchase_item(self, purchase):
self.__purchase=purchase
def get_total(self, total):
self.__total=total
def show_item(self, show):
self.__show=show
def clear(self, clear):
self.__clear=clear
#accessors
def acc_purchase(self):
return self.__purchase
def acc_total(self):
return self.__total
def acc_show(self):
return self.__show
def acc_clear(self):
return self.__clear
最后我的节目：
import retail_item
import cash_register
SHOW = 1
PURCHASE = 2
CART = 3
TOTAL = 4
EMPTY = 5
QUIT = 6
def main():
mylist = make_list()
#mycr = cash_register.CashRegister(mylist)
choice = 0
# Process menu selections until user quits program.
while choice != QUIT:
# Get the user's menu choice.
choice = get_menu_choice()
# Proces the choice.
if choice == SHOW:
show_items(mylist)
elif choice == PURCHASE:
purchase_item(mylist)
elif choice == TOTAL:
get_total(mylist)
elif choice == EMPTY:
clear(mylist)
def make_list():
item_list = {}
desc = 'Jacket'
inventory = 12
price = 59.95
entry = retail_item.RetailItem(desc, inventory, price)
item_list[desc]=entry
desc = 'Jeans'
inventory = 40
price = 34.95
entry = retail_item.RetailItem(desc, inventory, price)
item_list[desc]=entry
desc = 'Shirt'
inventory = 20
price = 24.95
entry = retail_item.RetailItem(desc, inventory, price)
item_list[desc]=entry
return item_list
# The get_menu_choice function displays the menu and gets
# a validated choice from the user.
def get_menu_choice():
print()
print('CASH REGISTER MENU')
print('-------------------------')
print('1. Show Retial Items')
print('2. Purchase Item(s)')
print('3. Show Current Shopping Cart')
print('4. Show Total of Items Purchased')
print('5. Empty Your Shopping Cart')
print('6. Quit the program')
print()
# Get the user's choice.
choice = int(input('Enter your choice: '))
# Validate the choice.
while choice < SHOW or choice > QUIT:
choice = int(input('Enter a valid choice: '))
# Return the user's choice.
return choice
def show_items(mylist):
print('\t\tDescription\t\tUnits in Inventory\t\tPrice')
print('--------------------------------------------------------------------------------')
x=1
for item in mylist:
print('Item #', x, '\t\t', item.get_desc(), '\t\t\t\t', item.get_inventory(), '\t\t\t$', format(item.get_price(), ',.2f'),sep='')
print()
x+=1
def purchase_item(mylist):
desc = input('Enter the item you wish to purchase: ')
if desc in mylist:
amount=int(input('How many would you like to buy: '))
if mylist[units]>0:
mylist[units]-=amount
elif (units-amount<0):
mylist[units]=0
else:
mylist[units] = 0
entry=cash_register.CashRegister(desc, units,)
mylist[desc]=entry
print()
def get_total(mylist):
print()
def clear(mylist):
print(mylist)
mylist.clear()
print(mylist)
main()
所以我的问题是，如何只更新一个类的一个对象？ 我如何调用cash_register类？
以下是分配的说明，如果有帮助的话：
本练习假设您已为Programming创建了RetailItem类 练习5.创建可与RetailItem类一起使用的CashRegister类。该 CashRegister类应该能够在内部保留RetailItem对象的列表。该 class应该有以下方法： •名为purchase_item的方法，它接受RetailItem对象作为参数。 每次调用purchase_item方法时，传递为的RetailItem对象 应该在列表中添加一个参数。 •名为get_total的方法，返回所有RetailItem对象的总价 存储在CashRegister对象的内部列表中。 •名为show_items的方法，显示有关存储的RetailItem对象的数据 在CashRegister对象的内部列表中。 •名为clear的方法，应清除CashRegister对象的内部列表。 在允许用户选择多个的程序中演示CashRegister类 购买物品。当用户准备结账时，程序应显示一个列表 他或她选择购买的所有物品以及总价格。
编辑： 这是我的最终代码。我知道它不漂亮，我为缺乏评论而道歉。我仍然会喜欢一些反馈，即使我很快会提交它（为了我自己的改善和工作机会！）这里是：
import retail_item
import cash_register
SHOW = 1
PURCHASE = 2
TOTAL = 3
EMPTY = 4
QUIT = 5
def main():
#set all variables to zero
lister = []
inv=[]
cost=[]
desc=''
inventory=0
price=0
total=0
purchase=0
#setting variable for each class
cash=cash_register.CashRegister(purchase, total, lister, inv, cost)
retail=retail_item.RetailItem(desc, inventory, price)
#classes
desc = 'Jacket'
inventory = 12
price = 59.95
#setting classes
retail.set_desc(desc)
retail.set_inventory(inventory)
retail.set_price(price)
#Adding to cart
cash.purchase_item(retail.get_desc(), lister)
cash.purchase_item(retail.get_inventory(), inv)
cash.purchase_item(retail.get_price(), cost)
desc = 'Jeans'
inventory = 40
price = 34.95
retail.set_desc(desc)
retail.set_inventory(inventory)
retail.set_price(price)
cash.purchase_item(retail.get_desc(), lister)
cash.purchase_item(retail.get_inventory(), inv)
cash.purchase_item(retail.get_price(), cost)
desc = 'Shirt'
inventory = 20
price = 24.95
retail.set_desc(desc)
retail.set_inventory(inventory)
retail.set_price(price)
cash.purchase_item(retail.get_desc(), lister)
cash.purchase_item(retail.get_inventory(), inv)
cash.purchase_item(retail.get_price(), cost)
choice = 0
# Process menu selections until user quits program.
while choice != QUIT:
# Get the user's menu choice.
choice = get_menu_choice()
# Proces the choice.
if choice == SHOW:
show_items(cash, retail, lister, inv, cost)
elif choice == PURCHASE:
purchase_item(cash, retail, lister, inv, cost)
elif choice == TOTAL:
get_total(cash, retail, lister)
elif choice == EMPTY:
price=0
cash.set_total(price)
clear(cash, lister)
# The get_menu_choice function displays the menu and gets
# a validated choice from the user.
def get_menu_choice():
print()
print('CASH REGISTER MENU')
print('-------------------------')
print('1. Show Retail Items')
print('2. Purchase Item(s)')
print('3. Show Total of Items Purchased')
print('4. Empty Your Shopping Cart')
print('5. Quit the program')
print()
# Get the user's choice.
choice = int(input('Enter your choice: '))
# Validate the choice.
while choice < SHOW or choice > QUIT:
choice = int(input('Please enter a valid choice: '))
# Return the user's choice.
return choice
def show_items(cash, retail, lister, inv, cost):
print('\t\tDescription\t\tUnits in Inventory\t\tPrice')
print('--------------------------------------------------------------------------------')
cash.show_item(lister, inv, cost)
def purchase_item(cash, retail, lister, inv, cost):
JACKET=1
JEANS=2
SHIRT=3
QUIT=4
choice=0
print()
print('WHICH WOULD YOU LIKE TO BUY')
print('-------------------------')
print('1. Jacket')
print('2. Jeans')
print('3. Shirt')
print('4. Quit')
print()
print('Choose as many as you like. Press 4 then ENTER to quit.')
while choice != QUIT:
# Get the user's menu choice.
choice = int(input('Which would you like to buy: '))
if choice < JACKET or choice > QUIT:
choice = int(input('Please enter a valid choice: '))
while choice != QUIT:
# Proces the choice.
if choice == JACKET:
desc = 'Jacket'
inventory = 12
price = 59.95
retail.set_desc(desc)
retail.set_inventory(inventory)
retail.set_price(price)
cash.purchase_item(retail.get_desc(), lister)
cash.purchase_item(retail.get_inventory(), inv)
cash.purchase_item(retail.get_price(), cost)
cash.set_total(price)
break
elif choice == JEANS:
desc = 'Jeans'
inventory = 40
price = 34.95
retail.set_desc(desc)
retail.set_inventory(inventory)
retail.set_price(price)
cash.purchase_item(retail.get_desc(), lister)
cash.purchase_item(retail.get_inventory(), inv)
cash.purchase_item(retail.get_price(), cost)
cash.set_total(price)
break
elif choice == SHIRT:
desc = 'Shirt'
inventory = 20
price = 24.95
retail.set_desc(desc)
retail.set_inventory(inventory)
retail.set_price(price)
cash.purchase_item(retail.get_desc(), lister)
cash.purchase_item(retail.get_inventory(), inv)
cash.purchase_item(retail.get_price(), cost)
cash.set_total(price)
break
print()
def get_total(cash, retail, lister):
print()
cash.show_items(cash.get_list(lister))
print('Your total is: $', format(cash.cost_total(),',.2f'))
def clear(cash, lister):
print('Shopping cart emptied.')
lister=lister.clear()
price=0
cash.set_total(price)
return lister
main()
RetailItem类：
class RetailItem:
def __init__(self, desc, inventory, price):
self.__desc=desc
self.__inventory=inventory
self.__price=price
#mutators
def set_desc (self, desc):
self.__desc=desc
def set_inventory (self, inventory):
self.__inventory=inventory
def set_price (self, price):
self.__price = price
#accessors
def get_desc(self):
return self.__desc
def get_inventory(self):
return self.__inventory
def get_price(self):
return self.__price
def __str__(self):
return 'Item Description:' + self.__desc, \
'\tNumber of Units:' + self.__inventory, \
'\tPrice: $' + self.__price
最后，我的CashRegister类：
#CashRegister Class
class CashRegister:
def __init__(self, purchase, total, lister, inv, cost):
self.__purchase=purchase
self.__total=total
self.__lister=[]
self.__inv=[]
self.__cost=[]
#mutators
def purchase_item(self, purchase, lister):
self.__purchase=purchase
lister.append(purchase)
return lister
def set_total(self, price):
self.__total+=price
def show_item(self, lister, inventory, price):
i=0
while i<len(lister):
s=('Item # %i\t%s\t\t\t\t%i\t\t\t%4.2f') % ((i+1),lister[i],inventory[i],price[i])
s = s.strip(' \t\n\r')
print(s)
i+=1
def show_items(self, lister):
i=0
print('You have purchased the following items')
while i<len(lister):
print(lister[i])
i+=1
def clear(self, lister):
i=0
while i<len(lister):
del lister[i]
i+=1
return lister
def get_list(self, lister):
return lister
#accessors
def acc_purchase(self):
return self.__purchase
def cost_total(self):
return self.__total
def acc_show(self):
return self.__show
def acc_clear(self):
return self.__clear
再次感谢你们！我经常使用这个网站，虽然我没有使用你们这次给我的很多东西，但你仍然很棒！
答案 0 :(得分：2)
此代码存在几个主要问题。没有堆栈跟踪我不能确切地说你为什么会得到一个AttributeError，但我可以告诉CashRegister对象不能被实例化为写入。它的__init__指的是不存在的变量 - 项和项。
您的CashRegister类正在为__init__提供不必要的参数 - 在某些情况下应该是方法。我没有看到任何理由你的CashRegister类应该采用任何__init__参数 - 它应该初始化RetailItem对象的列表，并且可能是一个正在运行的总计，不做任何其他事情。 purchase_item应该更新这些内部属性，get_total和show_items应该读取它们（或者get_total应该根据列表计算总数，如果你没有保持运行总计）并且clear应该重置它们。
在风格上，mutators和accessors以及隐藏的内部数据不是Pythonic习语。通常，Python类直接获取和设置成员数据，并在行为需要更改时重构以使用属性。我看到这是一个课/练习，所以你可能正在使用它们，因为它们是必需的，但如果没有，你最好没有它们。
修改的
这是我的main（）的样子，使最小的编辑显示逻辑：
def main():
items = make_list()
mycr = cash_register.CashRegister()
# at this point, mycr.show_items() should return [] and mycr.get_total() should return 0
choice = 0
while choice != QUIT:
choice = get_menu_choice()
if choice == SHOW:
mycr.show_items()
elif choice == PURCHASE:
item, quantity = get_purchase(items)
if item and quantity:
item.set_inventory(max(0, item.get_inventory() - quantity))
mycr.purchase_item(item, quantity)
elif choice == TOTAL:
print(mycr.get_total())
elif choice == EMPTY:
mycr.clear()
def get_purchase(items):
desc = input('Enter the item you wish to purchase: ')
if desc in items:
amount=int(input('How many would you like to buy: '))
return items[desc], amount
else:
return None, 0
这并未涵盖所有可能性 - 例如，与原始代码一样，除了将数量设置为0之外，它允许输入比当前可用的更高的数量而没有副作用。但是练习描述没有提到库存跟踪，所以也许这不是一个要求。