For anyone looking for argument parsing and serialization with Flask, I recommend webargs (http://webargs.readthedocs.org/), marshmallow (http://marshmallow.readthedocs.org), and flask-marshmallow (http://flask-marshmallow.readthedocs.org/).
You can actually use Spyne with Django as well[3] (and Spyne has a "general model serializer" that can be used with a lot less boilerplate than what's shown here).
Spyne supports a lot of protocols as well as persisting to a relational database via SQLAlchemy.
Disclaimer: I'm the author of spyne.
[1]: http://spyne.io
[2]: https://pypi.python.org/pypi/Flask-Spyne
[3]: https://github.com/arskom/spyne/tree/master/examples/django/...