How to get path of a python module ( not sys.executable )

I need to get Path for PyQt library in python program. Program is run as a script from another application, therefore my

sys.executable = 'D:/program files/visum/exe/visum115.exe

and I need my actual python path (and path for PyQt library module)

Path = C:\Python25\Lib\site-packages\PyQt4\plugins

im trying with

os.environ['PYTHONPATH']

but I'm not sure if it can be robust.

Regards!

PS. I need it to be able to plug plugins:

qApp.addLibaryPath('C:\Python25\Lib\site-packages\PyQt4\plugins')