root.py

class Root(Resource):

    __name__ = ''
    __parent__ = None

    def __init__(self, request):
        self.request = request

    def __getitem__(self, path):
        # /123
        if path.isdigit():
            entity = self.request.dbsession.query(Content).get(path)
            if not entity:
                raise KeyError
            elif isinstance(entity, Folder):
                return FolderResource(entity, self.request)
            elif isinstance(entity, Document):
                return DocumentResource(entity, self.request)
            elif isinstance(entity, Event):
                return EventResource(entity, self.request)
            else:
                raise KeyError