How do I permanently add an entry to sys.path in Python

Because Microsoft will be removing vbScript in the next version of Windows, I have been busy converting my utility vbScripts into Python. Part of this is a library of functions that I keep in D:\include. I'd like to maintain this system in Python, but the import process is rather clumsy. I have to

import sys
sys.path.insert(0,r'D:\include')

Only after that can I import a file. The documentation is somewhat obtuse but I gather my best option is to add the file D:\include__init__.py. As long as that folder is known to Python I could then do

from include import myfile1

to include the file D:\include\myfile1.py. The only problem is that I have yet to find a way to permanently add the include folder to the list of folders that Python searches. I'm sure there is a simple way. Anyone know what it is?