Python-сообщество

 class WidgetHandler:
    def __new__(cls, path, parent=None):
        ext = os.path.splitext(path)[1].replace('.', '')
        for subclass in cls.__subclasses__():
            if subclass.__name__.lower() == ext:
                return super().__new__(subclass)
        raise NotImplementedError
    def __init__(self, parent, path):
        self._path = path
        self._parent = parent
        self._is_modified = False  # Флаг для проверки был ли изменен файл
        self._create()
    def _create(self):
        raise NotImplementedError
    def _save(self):
        raise NotImplementedError
    def _close(self):
        raise NotImplementedError
    def save(self) -> None:
        if self._is_modified:
            self._save()
            self._is_modified = False
    def close(self) -> None:
        if self._is_modified:
            pass  # TODO Запрос сохранения
        self._close()

 class XML(WidgetHandler, QTreeView):
    def _create(self):
        self.setParent(self._parent)
        model = DomModel(self._path)
        # model.dataChanged.connect(lambda: print('Data Changed'))
        self.setModel(model)
        self.expandAll()
        self.setRootIsDecorated(False)
        self.setItemsExpandable(False)
        delegate = XMLDelegate()
        self.setItemDelegate(delegate)
    def _save(self):
        pass
    def _close(self):
        pass