day1-1

product_list = [
                ("电脑",5800),
                ("phone",4200),
                ("pen",66),
                ("book",99),
                ("watch",10800),
                ]

salary = input("输入工资:")
shopping_list = []
buy_money = 0
if salary.isdigit():
    salary = int(salary)
    while True:
        for index,value in enumerate(product_list):
            print(index,value)
        
        choice = input("输入产品编号：")
        if choice.isdigit():
            choice = int(choice)
            
            if choice >= 0 and choice < len(product_list):
                item = product_list[choice]
                if salary >= item[1]:
                    salary -= item[1]
                    buy_money += item[1]
                    shopping_list.append(item)
                    for i in shopping_list:
                        print (i)
                    print("你当前的余额是%d" % salary)
                else:
                    print("你当前的余额是%d,可用余额不足" % salary)
            else:
                print("没有此商品")
        elif choice == 'q':
            print("shopping list".center(50,'-'))
            for i in shopping_list:
                print(i)
            print("你购物消费%d元，当前的余额是%d" %(buy_money,salary))
            break
        else:
            print("输入'q'或者编号")
else:
    print("输入错误")

isdigit  判断输入是否由数字组成

enumerate print 把列表元素的编号和元素打印出来

append  添加元素方式

count = 5 
while count >= 0:
    print("count:%d" % count)
    count -= 1
else:
    print("跳出循环后打印count: %d" % count)

结果：

count:5
count:4
count:3
count:2
count:1
count:0
跳出循环后打印count: -1