MVC model structure in Python
Generally, we put it all in one file. This isn't Java or C++.
Start with a single file until you get some more experience with Python.  Unless your files are gargantuan, it will work fine.  
For example, Django encourages this style, so copy their formula for success.  One module for the model.  A module for each application; each application imports a common model.
Your Database and superclass stuff can be in your __init__.py file, since it applies to the entire package.  That may reduce some of the circularity.
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