EDIT: I'm going to run through the process step by step:
Preparing the sources:
exhuberant ctags, has an option: -x
Alternatively, ctags can generate a cross reference file which lists,
in human readable form, information about the various source objects
found in a set of language files.
This is the key to the problem:
ctags -x $(ls **/*.py); # replace with find if no zsh
will give you your database of source objects in a known, format, described under
man ctags; # make sure you use exuberant ctags!
Gnu Global is not limited to only the "out of the box" type of files. Any regular file format will serve.
Also, you can use gtags-cscope, which comes with global as mentioned in section 3.7 of the manual, for a possible shortcut using gtags. You'll end up with an input of a ctags tabular file which Global/gtags can parse to get your objects, or you can use the source for pycscope together with your ctags file of known format to get an input for the vim cscope commands in
if_cscope.txt.
Either way it's quite doable.
Perhaps you'd prefer idutils?
Definintely possible since
z3c.recipe.tags
on pypi makes use of both ctags and idutils to create tag files for a buildout, which is a method I shall investigate in short while.
Of course, you could always use the greputils script below, it has support for idutils , we know idutils works with python, and if that fails, there is also something called vimentry from this year that also uses python, idutils and vim.
Reference links ( not complete list ):
http://www.vim.org/scripts/script.php?script_id=893 ( Gnu global, updated 2008 )
http://www.vim.org/scripts/script.php?script_id=1062 ( greputils, contains support for the *id idutils, 2005 )
http://www.vim.org/scripts/script.php?script_id=251 ( Ancient, but this guy is pretty good, his tag and buffer howtos are amazing 2002 )
http://code.google.com/p/python-on-a-chip/source/browse/trunk/src/tools/pycscope.py?r=503 ( 2009, seems to be updates to pycscope)
Hopefully this helps you with your problem, I certainly helped me. I would have been quite sad tonight with a maggoty pycscope.