Python system with exemplary organization/coding style

[TomF]

I'm looking for a medium-sized Python system with very good coding 
style and good code organization, so I can learn from it.  I'm reading 
various books on Python with advice on such things but I'd prefer to 
see a real system.

By medium-sized I mean 5-20 classes, 5-20 files, etc; a code base that 
has some complexity but isn't overwhelming.

Thanks,
-Tom