三级菜单

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

'''
{
    '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":{},
    },
    '山东':{
        "德州":{},
        "青岛":{},
        "济南":{}
    },
    '广东':{
        "东莞":{},
        "常熟":{},
        "佛山":{},
    },
}
'''

#!/usr/bin/env python
# coding: utf-8
# Author: Yerban


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": {},
    },
    '山东': {
        "德州": {},
        "青岛": {},
        "济南": {}
    },
    '广东': {
        "东莞": {},
        "常熟": {},
        "佛山": {},
    },
}

# 标志位，只要不为True，就会一直循环
exit_flag = False
while not exit_flag:
    for a in data:
        print(a)
    user_choice1 = input("选择省份>>>:")

    if user_choice1 in data:
        while not exit_flag:
            for b in data[user_choice1]:
                print("\t", b)
            user_choice2 = input("选择地区>>>:")

            if user_choice2 in data[user_choice1]:
                while not exit_flag:
                    for c in data[user_choice1][user_choice2]:
                        print("\t\t", c)
                    user_choice3 = input("选择地标>>>:")

                    if user_choice3 in data[user_choice1][user_choice2]:
                        # 方法一
                        # while True:
                        #     for d in data[user_choice1][user_choice2][user_choice3]:
                        #         print("\t\t\t", d)
                        #     user_choice4 = input("已经到底了，请输入'q'返回!>>>:")
                        #     if user_choice4 == "q":
                        #         break
                        # 方法二
                        for d in data[user_choice1][user_choice2][user_choice3]:
                            print("\t\t\t", d)
                        user_choice4 = input("已经到底了，请输入'b'返回!>>>:")
                        if user_choice4 == "b":
                            pass  # 占位跳过
                        elif user_choice4 == "q":
                            exit_flag = True
                    if user_choice3 == "b":
                        break
                    elif user_choice3 == "q":
                        exit_flag = True
            if user_choice2 == "b":
                break
            elif user_choice2 == "q":
                exit_flag = True
    if user_choice1 == "b":
        break
    elif user_choice1 == "q":
        exit_flag = True