https://github.com/marshmallow-code/marshmallow-oneofschema

Marshmallow library extension that allows schema (de)multiplexing
https://github.com/marshmallow-code/marshmallow-oneofschema

hacktoberfest marshmallow polymorphic

Last synced: 10 months ago
JSON representation

Marshmallow library extension that allows schema (de)multiplexing

• Host: GitHub
• URL: https://github.com/marshmallow-code/marshmallow-oneofschema
• Owner: marshmallow-code
• License: mit
• Created: 2016-03-15T04:46:28.000Z (almost 10 years ago)
• Default Branch: main
• Last Pushed: 2025-04-07T18:39:00.000Z (10 months ago)
• Last Synced: 2025-04-13T03:59:57.376Z (10 months ago)
• Topics: hacktoberfest, marshmallow, polymorphic
• Language: Python
• Homepage:
• Size: 147 KB
• Stars: 139
• Watchers: 7
• Forks: 43
• Open Issues: 27
• Metadata Files:
  • Readme: README.rst
  • Changelog: CHANGELOG.rst
  • Funding: .github/FUNDING.yml
  • License: LICENSE
  • Security: SECURITY.md

Awesome Lists containing this project

README

          
=======================

marshmallow-oneofschema

=======================

|pypi| |build-status| |marshmallow3|

.. |pypi| image:: https://badgen.net/pypi/v/marshmallow-oneofschema

    :target: https://pypi.org/project/marshmallow-oneofschema/

    :alt: PyPI package

.. |build-status| image:: https://github.com/marshmallow-code/marshmallow-oneofschema/actions/workflows/build-release.yml/badge.svg

    :target: https://github.com/marshmallow-code/flask-marshmallow/actions/workflows/build-release.yml

    :alt: Build status

.. |marshmallow-support| image:: https://badgen.net/badge/marshmallow/3,4?list=1

    :target: https://marshmallow.readthedocs.io/en/latest/upgrading.html

    :alt: marshmallow 3|4 compatible

An extension to marshmallow to support schema (de)multiplexing.

marshmallow is a fantastic library for serialization and deserialization of data.

For more on that project see its `GitHub `_

page or its `Documentation `_.

This library adds a special kind of schema that actually multiplexes other schemas

based on object type. When serializing values, it uses get_obj_type() method

to get object type name. Then it uses ``type_schemas`` name-to-Schema mapping

to get schema for that particular object type, serializes object using that

schema and adds an extra field with name of object type. Deserialization is reverse.

Installing

----------

::

    $ pip install marshmallow-oneofschema

Example

-------

The code below demonstrates how to set up a polymorphic schema. For the full context check out the tests.

Once setup the schema should act like any other schema. If it does not then please file an Issue.

.. code:: python

    import marshmallow

    import marshmallow.fields

    from marshmallow_oneofschema import OneOfSchema

    class Foo:

        def __init__(self, foo):

            self.foo = foo

    class Bar:

        def __init__(self, bar):

            self.bar = bar

    class FooSchema(marshmallow.Schema):

        foo = marshmallow.fields.String(required=True)

        @marshmallow.post_load

        def make_foo(self, data, **kwargs):

            return Foo(**data)

    class BarSchema(marshmallow.Schema):

        bar = marshmallow.fields.Integer(required=True)

        @marshmallow.post_load

        def make_bar(self, data, **kwargs):

            return Bar(**data)

    class MyUberSchema(OneOfSchema):

        type_schemas = {"foo": FooSchema, "bar": BarSchema}

        def get_obj_type(self, obj):

            if isinstance(obj, Foo):

                return "foo"

            elif isinstance(obj, Bar):

                return "bar"

            else:

                raise Exception("Unknown object type: {}".format(obj.__class__.__name__))

    MyUberSchema().dump([Foo(foo="hello"), Bar(bar=123)], many=True)

    # => [{'type': 'foo', 'foo': 'hello'}, {'type': 'bar', 'bar': 123}]

    MyUberSchema().load(

        [{"type": "foo", "foo": "hello"}, {"type": "bar", "bar": 123}], many=True

    )

    # => [Foo('hello'), Bar(123)]

By default get_obj_type() returns obj.__class__.__name__, so you can just reuse that

to save some typing:

.. code:: python

    class MyUberSchema(OneOfSchema):

        type_schemas = {"Foo": FooSchema, "Bar": BarSchema}

You can customize type field with `type_field` class property:

.. code:: python

    class MyUberSchema(OneOfSchema):

        type_field = "object_type"

        type_schemas = {"Foo": FooSchema, "Bar": BarSchema}

    MyUberSchema().dump([Foo(foo="hello"), Bar(bar=123)], many=True)

    # => [{'object_type': 'Foo', 'foo': 'hello'}, {'object_type': 'Bar', 'bar': 123}]

You can use resulting schema everywhere marshmallow.Schema can be used, e.g.

.. code:: python

    import marshmallow as m

    import marshmallow.fields as f

    class MyOtherSchema(m.Schema):

        items = f.List(f.Nested(MyUberSchema))

License

-------

MIT licensed. See the bundled `LICENSE `_ file for more details.