Why is my system using my old PYTHONPATH after explicitly setting?

Question

I am running a script that explicitly sets the PYTHONPATH to avoid naming collisions. However, even if I say os.environ['PYTHONPATH'] = '', it looks as though the system is still able to find my old path that "lives" outside the script.

How is my system able to see the old PYTHONPATH even after I explicitly set it to a new one?

Answer 1

The PYTHONPATH environment variable is parsed at startup and inserted into sys.path. If you need to adjust the path from within your Python code, manipulate sys.path, not PYTHONPATH.