三级菜单

menu = {
    ‘北京‘: {
        ‘海淀‘: {
            ‘五道口‘: {
                ‘soho‘: {},
                ‘网易‘: {},
                ‘google‘: {}
            },
            ‘中关村‘: {
                ‘爱奇艺‘: {},
                ‘汽车之家‘: {},
                ‘youku‘: {},
            },
            ‘上地‘: {
                ‘百度‘: {},
            },
        },
        ‘昌平‘: {
            ‘沙河‘: {
                ‘老男孩‘: {},
                ‘北航‘: {},
            },
            ‘天通苑‘: {},
            ‘回龙观‘: {},
        },
        ‘朝阳‘: {},
        ‘东城‘: {},
    },
    ‘上海‘: {
        ‘闵行‘: {
            "人民广场": {
                ‘炸鸡店‘: {}
            }
        },
        ‘闸北‘: {
            ‘火车战‘: {
                ‘携程‘: {}
            }
        },
        ‘浦东‘: {},
    },
    ‘山东‘: {},
}

def threeLM(dic):
     while True:
        for k in dic:print(k)
        key = input(‘input>>‘).strip()
        if key == ‘b‘ or key == ‘q‘:return key # 输入b会return b本身，直接结束当前循环，返回上一级，不断输入b，直至结束
        elif key in dic.keys() and dic[key]: # 判断key在列表中，并且有内容不为空，则进行递归执行下一步
            ret = threeLM(dic[key])
            if ret == ‘q‘: return ‘q‘ #如果输入q，则直接退出


threeLM(menu)