Integration with mongodb?
I think you'll find that its better to use an existing library. Or be prepared to do a really close reading of the source code!
 Basically you're going to be dealing with replacing the database classes and the query compiler. The model and field semantics are probably different as well. Please comment if you'd like to discuss more, but frankly I think you're barking up the wrong tree.

I'm using Peewee in more and more projects now, but I'm currently working on a project in which we need to use MongoDB. Is there a way that I can make Peewee work with MongoDB? All tips are welcome!
