菜单实现功能
输入一层显示下一层菜单
不论在哪层输入b返回上一层
不论在哪层输入q退出菜单

此代码通过利用字典的知识可以实现
_Author_ = 'jc'
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':{}
    }
}
exit_flag = False
while not exit_flag:
    for i in data:
        print(i)
    choice = input('please input your choice:')
    if choice in data:
        while not exit_flag:
            for i2 in data[choice]:
                print(i2)
            choice2 = input('please input your choice2:')
            if choice2 in data[choice]:
                while not exit_flag:
                    for i3 in data[choice][choice2]:
                        print(i3)
                    choice3 = input('please input your choice3:')
                    if choice3 in data[choice][choice2]:
                        for i4 in data[choice][choice2][choice3]:
                            print(i4)
                        choice4 = input('please input b to exit:')
                        if choice4 == 'b':
                            pass
                        elif choice4 == 'q':
                            exit_flag = True
                    if choice3 == 'b':
                        break
                    elif choice3 =='q':
                        exit_flag = True
            if choice2 == 'b':
                break
            elif choice2 == 'q':
                exit_flag = True
    elif choice == 'q':
        exit_flag = True