Do any Python ORMs (SQLAlchemy?) work with Google App Engine?

Question

I'd like to use the Python version of App Engine but rather than write my code specifically for the Google Data Store, I'd like to create my models with a generic Python ORM that could be attached to Big Table, or, if I prefer, a regular database at some later time. Is there any Python ORM such as SQLAlchemy that would allow this?

Answer 1

Technically this wouldn't be called an ORM (Object Relational Mapper) but a DAL (Database Abstraction Layer). The ORM part is not really interesting for AppEngine as the API already takes care of the object mapping and does some simple relational mapping (see RelationProperty).

Also realize that a DAL will never let you switch between AppEngine's datastore and a "normal" sql database like mysql because they work very differently. It might let you switch between different key value stores, like reddis, mongo or tokyo cabinet. But as they all have such very different characteristics I would really think twice before using one.

Lastly, the DAL traditionally sits on top of the DB interface, but with AppEngine's api you can implement your own "stubs" that basically let you use other storage backends on their api. The people at Mongo wrote one for MongoDB which is very nice. And the dev_appserver comes with a filesystem-based one.

And now to the answer: yes there is one! It's part of web.py. I haven't really tried if for the reasons above, so I can't really say if it's good.

PS. I know Ruby has a nice DAL project for keyvalue stores in the works too, but I can't find it now... Maybe nice to port to Python at some point.

Answer 2

Nowadays they do since Google has launched Cloud SQL