MVC model structure in Python
I think you have one issue that should be straightened.  Circular references often result from a failure to achieve separation of concerns.  In my opinion, the database and model modules shouldn't know much about each other, working against an API instead.  In this case the database shouldn't directly reference any specific model classes but instead provide the functionality the model classes will need to function.  The model in turn, should get a database reference (injected or requested) that it would use to query and persist itself.
I'm having problems structuring classes in the Model part of an MVC pattern in my Python app. No matter how I turn things, I keep running into circular imports. Here's what I have:
Model/__init__p.y

should hold all Model class names so
I can do a "from Model import User"
e.g. from a Controller or a unit
test case

Model/Database.py 

holds Database class
needs to import all Model classes to do ORM
initialization should be performed on first module import, i.e. no extra init calls or instantiations (all methods on Database class are @classmethods)

Model/User.py

contains User model class
needs access to Database class to do queries
should inherit from base class common to all Model classes to share functionality (database persistency methods, parameter validation code etc.)

I have yet to see a real world Python app employing MVC, so my approach is probably un-Pythonic (and possibly a language-agnostic mess on top of that...) - any suggestions on how to solve this?
Thanks, Simon