三级菜单练习

data = {
    '北京':{
        '昌平':{
            '沙河':{'old_boy','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':[],
        '福州':[],
        '佛山':[]
    }
}
exit_flag = False
while not exit_flag:
    for i in data:
        print(i)
    choice = input("选择进入1>>:")
    if choice in data:
        while not exit_flag:
            for i2 in data[choice]:
                print("\t",i2)
            choice2 = input("选择进入2>>:")
            if choice2 in data[choice]:
                while not exit_flag:
                    for i3 in data[choice][choice2]:
                        print("\t\t",i3)
                    choice3 = input("选择进入3>>:")
                    if choice3 in data[choice][choice2]:
                        while not exit_flag:
                            for i4 in data[choice][choice2][choice3]:
                                print("\t\t\t",i4)
                            choice4 = input("选择进入4>>:")
                            if choice4 == "b":
                                break
                            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
    if choice == "q":
        exit_flag = True