Python学习之路 002

　　今天写着购物车的作业,最头疼的是文件操作了

尤其是文件的打开模式　　w　　r　　a　　最TM的头疼

r+模式可读可写,但是写的内容会根据文件指针去覆盖之前的内容,当文件需要修改时,强烈建议不要用这种模式,会有一个坑

下面说说文件的思路吧,还没有学习函数,因此代码起来很乱

　　1.设置接口　　

　　　　#user接口

if ident_flag == ‘u‘:

　　　　　　首先读入文件的数据

    #    商品信息
    with open("goods.txt",‘r‘) as goods_file:
        goods_info = {}
        for line in goods_file.readlines():
            item = line.strip(‘\n‘).split(‘ ‘)
            goods_info[item[0]] = item[1]
    #    余额信息
    with open("balance.txt",‘r‘) as balance_file:
        balance = int( balance_file.readline().strip(‘\n‘) )

　　　　　　购买商品

        #    购买商品
        buy_name = input("Which goods would your like to buy?(input the name of goods)>>: ")
        if buy_name in goods_info:
            if balance > int( goods_info[buy_name] ):
                balance =  balance - int( goods_info[buy_name] )
                shopping_list[buy_name] = goods_info[buy_name]
            else:
                print("I‘m sorry to hear that you have not enough money to buy this")
        else:
            print("Sorry sir, there is not the goods that you need!!\n")

　　　　　　结账

     #    结算
    with open("balance.txt",‘w‘) as goods_file:
        goods_file.write(str(balance))

　　　　#manager接口

elif ident_flag == ‘m‘:

　　　　　　首先读入文件

    #   商品信息
    with open("goods.txt",‘r‘) as goods_file:
        goods_info = {}

        for line in goods_file.readlines():
            item = line.strip(‘\n‘).split(‘ ‘)
            goods_info[item[0]] = item[1]

　　　　　　增加商品

        #    增加商品
        if choice == ‘a‘:

            print("you are adding a goods".center(50,‘-‘))
            goods_name = input("The goods_name is: ")
            goods_price = input("The goods_price is: ")
            print("\n".rjust(51,‘-‘))

            info = goods_name + ‘ ‘ + goods_price + ‘\n‘
            with open("goods.txt", ‘a‘) as goods_file:
                goods_file.write(info)

　　　　　　修改商品

        #    修改商品
        elif choice == ‘m‘:

                print("You are modify a goods".center(50, ‘-‘))
                goods_name = input("The goods_name is: ")
                if goods_name in goods_info:

                    goods_price = input("The goods_price is: ")
                    goods_info[goods_name] = goods_price

                    with open("goods.txt", ‘w+‘) as goods_file:
                        for item in goods_info:
                            info = item + ‘ ‘ + goods_info[item] + ‘\n‘
                            goods_file.write(info)
                else:
                    print("Sorry sir, there is not -{_goods_name}-!".format(_goods_name = goods_name))

　　　　　　删除商品

        #    删除商品
        elif choice == ‘d‘:
                print("you are delete a goods".center(50, ‘-‘))
                goods_name = input("The goods_name is: ")
                if goods_name in goods_info:
                    goods_info.pop(goods_name)

                    with open("goods.txt",‘w‘):
                        for item in goods_info:
                            info = item + ‘ ‘ + goods_info[item] + ‘\n‘
                            goods_file.write(info)