三级菜单案例

#Author:donghuiyadata={    '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":["Avent","飞信"],        },        "海淀":{},    },    '山东':{        "德州":{},        "青岛":{},        "济南":{}    },    '广东':{        "东莞":{},        "常熟":{},        "佛山":{},    },}exit_flag=Falsewhile not exit_flag:    for i in data:        print(i)    choice=input("选择进入1>>")#北京    if choice in data:        while not exit_flag:            for i2 in data[choice]:                print(i2)            choice2=input("选择进入2>>")#昌平            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:>>")#沙河                    if choice3 in data[choice][choice2]:                        for i4 in data[choice][choice2][choice3]:#【】                            print("\t\t",i4)                        choice4=input("最后一层，按b返回>>:")                        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