[Python] How to set pythonpath in Mac OS X?

Hello Pythonistas,

I am trying to get certain (self-written) libraries imported into my
scripts using statements like

"from library import function.py".

But they are not being found.

I think that the pythonpath-variable must be expanded to the location
to this libraries.

But, I can't find any usable information using Google on how to set up
the pythonpath properly.
I don't even know where to look for the pythonpath-variable?

It would be great if anyone could help me out on this?

Thanks,
Eric