In addition to the Framework Overview and Best Practices documents which will inform you as to the way the separation of concerns is achieved here, you can also check out the Python demos at: http://trac.puremvc.org/PureMVC_Python/
The documents above are written with examples of Flex and AS3 but don't let that put you off. The framework eschews platform- and language- specific features in order to be broadly portable. So, although you may not be a Flex/AS3 person, you should be able to get the idea easily. In fact I don't know Python but I understand the demos perfectly because they follow the same methodology.