python 购物车和三级菜单

程序：购物车程序

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，够就直接扣款，不够就提醒 
4. 可随时退出，退出时，打印已购买商品和余额

#-*- coding:utf8 -*-
shopping_list=[]
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]
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("请选择您要买的商品：")
        if user_choice.isdigit():
            user_choice=int(user_choice)
            if user_choice<len(product_list) and user_choice>=0:
                item_choice=product_list[user_choice]
                if item_choice[1]<=salary:
                    print ("买的起")
                    shopping_list.append(item_choice)
                    salary-=item_choice[1]
                    print("将您的商品%s加入购物车,余额%s" %(item_choice,salary))
                else:
                    print("余额不够:",salary)
            else:
                print("商品不存在")
        elif user_choice=='q':
            print("--打印商品列表-----")
            for i in product_list:
                print(i)
                print("您当前的余额：",salary)
                exit()
        else:
                print ("不正确")

程序: 三级菜单

要求: 

1. 打印省、市、县三级菜单
2. 可返回上一级
3. 可随时退出程序

#-*- coding:utf8 -*-
data = {
    '北京':{
        "昌平":{
            "沙河":["oldboy","test"],
            "天通苑":["链家地产","我爱我家"]
        },
        "朝阳":{
            "望京":["奔驰","陌陌"],
            "国贸":{"CICC","HP"},
            "东直门":{"Advent","飞信"},
        },
        "海淀":{},
    },

    '广东':{
        "东莞":{},
        "常熟":{},
        "佛山":{},
    },
}

exit_flag=True
while exit_flag:
    for i in data:
        print(i)
    choice=input("请选择入口：")
    if choice in data:
        while exit_flag:
            for i2 in data[choice]:
                print("		",i2)
            choice2=input("请选择入口2：")
            if choice2 in data[choice]:
                while exit_flag:
                    for i3 in data[choice][choice2]:
                        print("		",i3)
                    choice3=input("请选择入口3：")
                    if choice3 in data[choice][choice2]:
                            for i4 in data[choice][choice2][choice3]:
                                print("		", i4)
                            choice4=input("最后一层按b返回：")
                            if choice4=='b':
                                pass
                            if choice4=='q':
                                exit_flag=False
                    if choice3=="b":
                        break
                    elif choice3=="q":
                        exit_flag=False
            if choice2=="b":
                break
            elif choice2=="q":
                exit_flag=False