项目要求：

1、增强版购物车是利用了文件系统，保存用户的购物列表和当前余额信息，在用户每次购物前先读取用户当前余额后再进行购买，并把购买的物品名称存到列表中；

2、用文件系统保存商品明细，不用每次都进行人工输入

程序要点：

1、文件读写操作

2、把一个格式化的文件内容读取到列表中，并对不需要的\n等信息进行处理，得到有效的格式化数据

待改进：

程序结构化不够，比较乱，后面可以函数化进行封装

'''用户入口:    1、商品信息存在文件里    2、已购商品，余额记录    商家入口：    1、可以添加商品，修改商品价格'''# 用户入口：# 从文件中读取所有商品信息到字典中

f_product_list = open(r"C:\Users\Administrator\PycharmProjects\S14Week2\product", 'r')f_shopping_list = open(r"C:\Users\Administrator\PycharmProjects\S14Week2\shoppinglist", 'r+')product_list = []shopping_list = []length = 0while True:    product_list_temp = f_product_list.readline()    # product_list_temp.strip()    if product_list_temp == "" or product_list_temp == "\n":        break    # print("RAW Line is :",product_list_temp)    product_list_temp = product_list_temp.strip()    # print("Strip result is :", product_list_temp)    product_list_temp = product_list_temp.split(",")    # print("Split result is :",product_list_temp)    # product_list_temp = product_list_temp.strip()    # print(product_list_temp)    product_list.append(product_list_temp)# print("Final result is :",product_list)product_list = list(product_list)salary = 0while True:    shopping_list_temp = f_shopping_list.readline()    if shopping_list_temp == "" or shopping_list_temp == "\n":        break    # print("RAW Line is :",product_list_temp)    shopping_list_temp = shopping_list_temp.strip()    # print("Strip result is :", product_list_temp)    shopping_list_temp = shopping_list_temp.split(",")    # print("Split result is :",product_list_temp)    # product_list_temp = product_list_temp.strip()    # print(product_list_temp)    shopping_list.append(shopping_list_temp)    salary = int(shopping_list_temp[1])

shopping_list = list(shopping_list)# print("Final result is :",product_list)print("Notice, this is salary:",salary)product_list = list(product_list)if salary == None:    salary = input("Input your salary:")    if salary.isdigit():        salary = int(salary)

while True:    for index, item in enumerate(product_list):        print(index, item)    choice = input("Input your choice:")    if choice.isdigit():        choice = int(choice)        if choice < len(product_list) and choice >= 0:            p_item = product_list[choice]            print(p_item)            if int(p_item[1]) <= salary:  # 买得起                shopping_list.append(p_item)                salary -= int(p_item[1])                f_shopping_list.write(p_item[0])                f_shopping_list.write(",")                f_shopping_list.write(str(salary))                f_shopping_list.write("\n")                print("Added %s into shoppint cart, your current balance is %s" % (p_item, salary))            else:                print("Sorry, your money is not enough!")        else:            print("Product is not exist")    elif choice == 'q':        print("Your current balance is ", salary)        f_shopping_list.close()        f_product_list.close()        break