Understanding other people's code

[L O'Shea]

Hi all,
I've been asked to take over a project from someone else and to extend the functionality of this. The project is written in Python which I haven't had any real experience with (although I do really like it) so I've spent the last week or two settling in, trying to get my head around Python and the way in which this code works.

The problem is the code was clearly written by someone who is exceptionally good and seems to inherit everything from everywhere else. It all seems very dynamic, nothing is written statically except in some configuration files. 
Basically the problem is I am new to the language and this was clearly written by someone who at the moment is far better at it than I am!

I'm starting to get pretty worried about my lack of overall progress and so I wondered if anyone out there had some tips and techniques for understanding other peoples code. There has to be 10/15 different scripts with at least 10 functions in each file I would say.

Literally any idea will help, pen and paper, printing off all the code and doing some sort of highlighting session - anything! I keep reading bits of code and thinking "well where the hell has that been defined and what does it mean" to find it was inherited from 3 modules up the chain. I really need to get a handle on how exactly all this slots together! Any techniques,tricks or methodologies that people find useful would be much appreciated.