Permanently add a directory to PYTHONPATH?

Question

Whenever I use sys.path.append, the new directory will be added. However, once I close python, the list will revert to the previous (default?) values. How do I

Answer 1

Shortest path between A <-> B is a straight line;

import sys
if not 'NEW_PATH' in sys.path:
  sys.path += ['NEW_PATH']