0

在下面编辑！

这是我的retail_item 类：

#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

还有我的收银员课：

#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

最后是我的程序：

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？

以下是作业说明，如果有帮助的话：

本练习假定您已为编程练习 5 创建了 RetailItem 类。创建可与 RetailItem 类一起使用的 CashRegister 类。CashRegister 类应该能够在内部保留一个 RetailItem 对象列表。该类应具有以下方法： • 一个名为 purchase_item 的方法，它接受一个 RetailItem 对象作为参数。每次调用 purchase_item 方法时，应将作为参数传递的 RetailItem 对象添加到列表中。• 名为get_total 的方法返回存储在CashRegister 对象的内部列表中的所有RetailItem 对象的总价。• 一个名为show_items 的方法，它显示有关存储在CashRegister 对象的内部列表中的RetailItem 对象的数据。• 一个名为 clear 的方法，它应该清除 CashRegister 对象的内部列表。在一个程序中演示 CashRegister 类，该类允许用户选择多个要购买的项目。当用户准备结账时，程序应该显示他或她选择购买的所有物品的清单，以及总价。

编辑：这是我的最终代码。我知道它不漂亮，我为缺乏评论表示歉意。我仍然想要一些反馈，即使我很快就会提交（为了我自己的进步和工作机会！）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()

零售项目类：

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

再说一次，最后是我的 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

再次感谢各位！我经常使用这个网站，虽然这次我没有使用你们给我的很多东西，但你仍然很棒！

4

1 回答 1

2

这段代码有几个主要问题。如果没有堆栈跟踪，我无法准确说明为什么您会收到 AttributeError，但我可以告诉您 CashRegister 对象无法按书面形式实例化。它__init__指的是不存在的变量 - item 和 items。

您的 CashRegister 类正在接受__init__不必要的参数 - 在某些情况下应该是方法。我看不出你的 CashRegister 类应该接受任何__init__参数的任何理由——它应该初始化 RetailItem 对象的列表，并且可能是一个运行总计，并且什么都不做。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，如果您不保留运行总计）并且 clear 应该重置它们。

从风格上讲，mutators 和 accessors 以及隐藏的内部数据不是 Pythonic 的习惯用法。一般来说，Python 类直接获取和设置成员数据，并在行为需要更改时进行重构以使用属性。我看到这是针对课程/练习的，因此您可能正在使用它们，因为它们是必需的，但如果不是，您最好没有它们。

编辑

这就是我的 main() 的样子，进行最少的编辑以显示逻辑：

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

这并不涵盖所有可能性 - 例如，与您的原始代码一样，它允许输入比当前可用的数量更高的数量，除了将数量设置为 0 之外没有副作用。但是练习描述没有提到库存跟踪，所以也许那是不是要求。

于 2013-05-02T20:17:57.533 回答