Kim is a Serialization and Marshaling framework. Arrested provides out of the box integration with Kim, providing you with the ability to serialize and deserialize complex object types.

You can read more about Kim at Read the docs. or check out the source code on GitHub.

Let’s refactor the Characters resource from the quickstart example application to integrate with Kim.


from arrested.contrib.kim_arrested import KimEndpoint
from kim import Mapper, field, role

class CharacterMapper(Mapper):
    __type__ = Character

    id = field.Integer(read_only=True)
    name = field.String()
    created_at = field.Datetime(read_only=True)

class CharactersIndexEndpoint(KimEndpoint, GetListMixin, CreateMixin):

    name = 'list'
    many = True
    mapper_class = CharacterMapper

    def get_objects(self):

        characters = db.session.query(Character).all()
        return characters

    def save_object(self, obj):

        return obj

class CharacterObjectEndpoint(KimEndpoint, GetObjectMixin,
                              PutObjectMixin, DeleteObjectMixin):

    name = 'object'
    url = '/<string:obj_id>'
    mapper_class = CharacterMapper

    def get_object(self):

        obj_id = self.kwargs['obj_id']
        obj = db.session.query(Character).filter( == obj_id).one_or_none()
        if not obj:
            payload = {
                "message": "Character object not found.",
            self.return_error(404, payload=payload)

        return obj

    def update_object(self, obj):


        return obj

    def delete_object(self, obj):


So what’s changed? Firstly we are now using the KimEndpoint class when defining our Endpoints. This Custom base Endpoint does the grunt work for us. It defines the custome Kim Response and Request handlers and the get_response_handler_params and get_request_handler_params methods to set them up.

This has had some impact on our CharactersIndexEndpoint and CharacterObjectEndpoint too. We no longer need to manually instantiate the Character model ourselves and we’ve thankfully removed that really basic validation from the update_object method. Kim now provides robust validation of the data coming into our API ensuring data is present and of the correct type.