python 三级菜单操作

address_info = {
    "中国":{
            "山西":{
                "太原":["小店","迎泽"],
                "长治":["长子","长治县"]
            },
            "陕西":["汉中","咸阳"],
            "河北":["石家庄","邯郸"]
            },
    "美国":{
            "纽约":["a","b"],
            "迈阿密":["c","d"],
            "休斯顿":["e","f"]
            }
    }
exit_flag = True

while  exit_flag:
    for i in address_info:
        print (i)
    choice = input ("选择进入1>>:")
    if choice in address_info:
        while exit_flag:
            for i2 in address_info[choice]:
                print ("\t",i2)
            choice2 = input("选择进入2>>:")
            if choice2 in address_info[choice]:
                while exit_flag:
                    for i2 in address_info[choice][choice2]:
                        print ("\t",i2)
                    choice3 = input("选择进入3>>:")
                    if choice3 in address_info[choice][choice2]:
                        while exit_flag:
                            for i3 in address_info[choice][choice2][choice3]:
                                print("\t", i3)
                            choice4 = input ("按b返回：")
                            if choice4 == "b":
                                break
                            elif choice4 == "q":
                                exit_flag = False
                    if choice3 == "b":
                        break
                    elif choice3 == "q":
                        exit_flag = False
            if choice2 == "b":
                 break
            elif choice2 == "q":
                 exit_flag = False
    if choice == "b":
        pass
    elif choice == "q":
         exit_flag = False