Thanks to both of you for the response . I try to insert pdb breakpoint at some point in the code files and start the service. Then I issue a nova command to check how the flow works. From then on I use the pdb commands to check the function calls. This to me gives a very convenient way of learning the code connections, since I don't have an idea of how these functions and modules r related.  U people as developers have a design to start with and work on from there. So u may know the purpose of each function, class, etc.

Since nova api doesn't support pdb becos of eventlet design, I learned to print those objects and find their information.

But with pdb, it's a smooth flow to inspect the class attributes, their functions, arguments, types etc. I can even test those objects the python way since pdb supports python prompt as well. Of course I do all this on dev systems though...