1.需求：     1：启动程序后，让用户输入工资，然后打印商品列表     2：允许用户根据商品编号购买商品     3：用户选择商品后，检测余额是否够，够就直接付款，不够就提醒     4：可随时推出，推出时，打印已购买商品和余额

2.代码如下：

__author__ = "B J"product_list = [    ('Iphone',5800),    ('Mac Pro',9800),    ('Bike',800),    ('Watch',10600),    ('Coffee',31),]shopping_list = []salary = input("Input your salary:")if salary.isdigit():    salary = int(salary)    while True:        for index,item in enumerate(product_list):            #print(product_list.index(item),item)            print(index,item)        user_choice = input("选择要买嘛？>>>:")        if user_choice.isdigit():            user_choice = int(user_choice)            if user_choice < len(product_list) and user_choice >=0:                p_item = product_list[user_choice]                if p_item[1] <= salary: #买的起                    shopping_list.append(p_item)                    salary -= p_item[1]                    print("Added %s into shopping cart,your current balance is \033[31;1m%s\033[0m" %(p_item,salary) )                else:                    print("\033[41;1m你的余额只剩[%s]啦，还买个毛线\033[0m" % salary)            else:                print("product code [%s] is not exist!"% user_choice)        elif user_choice == 'q':            print("--------shopping list------")            for p in shopping_list:                print(p)            print("Your current balance:",salary)            exit()        else: