python学习：跳出while循环的用法 exit_flag = False while not exit_flag:

三级菜单：此处不足 没有考虑是否在data里面# -*- coding:utf-8 -*-# Author :dengdata = {    '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":{}    }}exit_flag = Falsewhile not exit_flag:    for i in data:        print(i)    choice = input('请选择进入》》1:')    if choice in data:        while not exit_flag:            for i2 in data[choice]:                print('\t',i2)            choice2 = input('请选择进入》》2:')            if choice2 in data[choice]:                while not exit_flag:                    for i3 in data[choice][choice2]:                        print('\t\t',i3)                    choice3 = input('请选择进入》》3:')                    if choice3 in data[choice][choice2]:                        for i4 in data[choice][choice2][choice3]:                                print('\t\t\t',i4)                        choice4 =input('最后一层，输入b返回,退出选择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