python學習：跳出while循環的用法 exit_flag = False while not exit_flag:

三級菜單：
此處不足 沒有考慮是否在data里面

# -*- coding:utf-8 -*-
# Author :deng
data = {
    '北京':{
        "昌平":{
            "沙河":["oldboy","test"],
            "天通苑":["鏈家地產","我愛我家"]
        },
        "朝陽":{
            "望京":["奔馳","陌陌"],
            "國貿":{"CICC","HP"},
            "東直門":{"Advent","飛信"},
        },
        "海淀":{},
    },
    '山東':{
        "德州":{},
        "青島":{},
        "濟南":{}
    }
}
exit_flag = False
while not exit_flag:
    for i in data:
        print(i)
    choice = input('請選擇進入》》1:')
    if choice in data:
        while not exit_flag:
            for i2 in data[choice]:
                print('\t',i2)
            choice2 = input('請選擇進入》》2:')
            if choice2 in data[choice]:
                while not exit_flag:
                    for i3 in data[choice][choice2]:
                        print('\t\t',i3)
                    choice3 = input('請選擇進入》》3:')
                    if choice3 in data[choice][choice2]:
                        for i4 in data[choice][choice2][choice3]:
                                print('\t\t\t',i4)
                        choice4 =input('最后一層，輸入b返回,退出選擇q：')
                        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