Hi there!
I have 2 solutions for this which might work:
1) Define PYTHONPATH in an /etc/profile.d script and then export it so you don't have to worry about it (at runtime either).
2) Since sys.path is just a list (in the python sense), you can simply append the respective directory with
Code:
sys.path.append("/path/to/whereever")
# Or perhaps you'd like to check first: if "/path/to/whereever" not in sys.path: sys.path.append("/path/to/whereever")
I believe both solutions should work for both python2 and python3.