product_list = [('iPhone',5800),('Mac Pro',9500),('Bike',800), ('Apple Watch',10600),("Coffee",31),("Alex Python",120)] shopplist_list = [] salary = input("Input your salary:") if salary.isdigit(): salary = int(salary) while True: for index,item in enumerate(product_list): print(index,item) user_choice = input("你选择要买:") 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: shopplist_list.append(p_item) salary = salary - p_item[1] print("added %s into shopping cart,you current balance is %s"%(p_item,salary)) else: print("你的余额只剩[%s]啦，余额不足" % salary) else: print("product code [%s] is not exist!" % user_choice) elif user_choice == 'q': print("------shooping list------") for p in shopplist_list: print(p) print("your current balance:",salary) exit() else: print("invalid option")