DAY 2 三级菜单

dic = {
    '山西':{
        '太原':
            {'小店':['锦都苑'],
            '迎泽':['铁路局']
             },
        '朔州':
            {
             '应县':['北河种'],
            '怀仁':['任村']
            }
          },
    '北京':
        ['丰台','海淀']
}
flag = True
while True:
    for i in dic:
        print(i)
    user_choice = input('请选择进入1（q返回上级菜单，按e回到根菜单）>>')
    while flag:
        if user_choice in dic:
            for i2 in dic[user_choice]:
                print(i2)
            while flag:
                user_choice1 = input('请选择进入2（q返回上级菜单，按e回到根菜单）>>')
                if user_choice1 in dic[user_choice]:
                    for i3 in dic[user_choice][user_choice1]:
                        print(i3)
                    while flag:
                        user_choice2 = input('请选择进入3（q返回上级菜单，按e回到根菜单）>>')
                        if user_choice2 in dic[user_choice][user_choice1]:
                            for i4 in dic[user_choice][user_choice1][user_choice2]:
                                print(i4)
                        elif user_choice2 == 'q':
                            for i3 in dic[user_choice][user_choice1]:
                                print(i3)
                            break
                        elif user_choice == 'e':
                            flag = False
                        else:
                            print('输入无效，请重新选择！')
                elif user_choice1 == 'q':
                    for i2 in dic[user_choice]:
                        print(i2)
                    break
                elif user_choice1 == 'e':
                    flag = False
        elif user_choice in 'qe':
            exit()
        else:
            print('输入无效，请重新选择')
            continue