Python2转Python3时wx应用shelve反序列化Rect TypeError问题

• 基于wxPython的绘图应用，支持在画布绘制各类对象、点击编辑参数，关闭时用shelve库保存修改，Python2环境下运行正常。
• 迁移到Python3后，添加一种仅用于图标间连线的特定对象，保存文件正常，但重新打开项目时失败。
• 报错为反序列化shelf对象时的TypeError，提示Rect()参数不匹配，无完整调用栈。
• 特殊现象：Python2生成的文件经转换后可打开，但再次保存关闭后仍会触发该错误。
• 已自定义继承pickle.Unpickler的类，重写find_class方法处理模块重命名（将wx._gdi映射到wx），且代码中未直接调用Rect，问题排查难度大。

报错详情 #

File "\Unpickle.py", line 25, in renamed_load
    return RenameUnpickler(file_obj, encoding=encoding).load()
TypeError: Rect(): arguments did not match any overloaded call:
  overload 1: too many arguments
  overload 2: not enough arguments
  overload 3: argument 1 has unexpected type 'float'
  overload 4: argument 1 has unexpected type 'float'
  overload 5: argument 1 has unexpected type 'float'
  overload 6: argument 1 has unexpected type 'float'

相关读取操作代码 #

class RenameUnpickler(pickle.Unpickler):
    def find_class(self, module, name):
        renamed_module = module
        if module == "wx._gdi":
            renamed_module = "wx"
        return super(RenameUnpickler, self).find_class(renamed_module, name)

def renamed_load(file_obj, encoding):
    return RenameUnpickler(file_obj, encoding=encoding).load()

def renamed_loads(pickled_bytes):
    file_obj = io.BytesIO(pickled_bytes)
    return renamed_load(file_obj)

class ShelfFileVO( shelve.DbfilenameShelf ):

    def __init__(self, *args, **kwds):
        kwds[ 'protocol' ] = 2
        shelve.DbfilenameShelf.__init__( self, *args, **kwds )
        self._semaphore = threading.BoundedSemaphore( 1 )
        self.find_globals = None

    def keys(self):
        return [ k.decode() for k in self.dict.keys() ]

    def has_key(self, key):
        return key.encode() in self.dict

    def __contains__(self, key):
        return key.encode() in self.dict

    def get(self, key, default=None):
        #key = key.encode()
        if key in self.dict:
            return self[ key ]
        else:
            return default

    def __getitem__(self, key):
        #key = key.encode()
        if key in list(self.cache.keys()):
            value = self.cache[ key ]
        else:
            f = BytesIO( self.dict[ key ] )
            value = renamed_load(f, encoding='latin1')

内容的提问来源于stack exchange，提问作者SickNebo