文件操作_菜单<代码>

info文件中的内容为：

{
    "河北省": {"石家庄": {"无极县":"", "高邑县":"", "灵寿县":"", "行唐县":"", "元氏县":""},
             "唐山市": {"乐亭县":"", "迁西县":"", "滦南县":"", "丰润区":"", "古冶区":""},
             "邯郸市": {"大名县":"", "临漳县":"", "邯郸县":"", "肥乡县":"", "永年县":""},
             "保定市": {"高阳县":"", "容城县":"", "望都县":"", "安新县":"", "顺平县":""}
             },
    "河南省": {"郑州市": {"中原区":"", "二七区":"", "金水区":"", "惠济区":"", "管城区":""},
             "开封市": {"龙亭区":"", "鼓楼区":"", "顺河区":"", "祥符区":"", "通许县":""},
             "安阳市": {"安阳县":"", "汤阴县":"", "内黄县":"", "文峰区":"", "北关区":""},
             "新乡市": {"红旗区":"", "卫滨区":"", "牧野区":"", "凤泉区":"", "卫辉市":""}
             },
    "湖北省": {"武汉市": {"武昌区":"", "汉阳区":"", "江岸区":"", "江夏区":"", "洪山区":""},
             "襄阳市": {"宜城市":"", "枣阳市":"", "樊城区":"", "襄州区":"", "南漳县":""},
             "宜昌市": {"当阳市":"", "点军区":"", "西陵区":"", "猇亭区":"", "伍家岗":""},
             "黄冈市": {"黄州区":"", "麻城市":"", "武穴市":"", "罗田县":"", "团风县":""},
             },
     }

 f = open("info","r+",encoding="utf8")
 a = eval(f.read())    # a点没用
 menu = dict(a)
 current_layer = menu                           # 为了动态循环，初始值为menu
 f.close()
 parent_layer = []  # 记录下父层，若是用一个变量来保存则back时，会原地返回

 while True:
     a = list(sorted(current_layer))                     # 排序key保证每次都一样的排序
     for i,key in enumerate(a,1):
         print(i,">>>",key)                             # 循环打印当前层的key
     chioce = input("输入序号 [q]退出 [b]返回（[more]进入管理选项：）").strip()
     if len(chioce) == 0:continue             # 什么都没输入的时候，在打印当前层的信息
     if chioce.isdigit():
         chioce = int(chioce)
         if 0 < chioce <= len(a):
             parent_layer.append(current_layer)      # *  在当前层还是子层时记录下来 因为马上它要变成父亲了
             current_layer = current_layer[a[chioce-1]]  # 为了下一次的循环将当前层换成用户输入的下一层
             if not current_layer:                    # 此时当前层为空
                 print("已经是最后一级菜单")
     elif chioce == "b":                       # 这一段的代码是防止回到最上一层时发生错误
         if parent_layer:                        # 判断父层记录器是空（False）时，表示回到第一层了，回到while继续打印第一层
             current_layer = parent_layer.pop()  # 若是有东西时（Ture）时，原先记录的本层删除了，然后上面执行上一次记录的父层。
     elif chioce == "more":
         chioce_m = input("[a]添加当前信息 [d]删除当前信息 [q]退出")
         if chioce_m =="a":
             a_add = input("输入想添加的信息：")
             current_layer.update({a_add:{}})           # 添加的是字典的嵌套，这样下次添加时仍旧是字典嵌套
         elif chioce_m == "d":
             a_del = int(input("输入序号"))
             del current_layer[a[a_del-1]]
         else:
             print("无此项")
         save_m = input("是否保存当前修改的信息？y or n:")  # 加在这个if语句中的好处是只有more的操作后才会提示保存
         if save_m == "y":
             menu_str = str(menu)
             f_m = open("info", "w", encoding="utf8")
             f_m.write(menu_str)                               # 保存的方式是以写的模式打开，类似于刷新。
         elif save_m == "n":
             pass
         else:
             print("无此项")
     elif chioce == "q":
         break
     else:
         print("无此项")