How to add to the PYTHONPATH in Windows, so it finds my modules/packages?
While this question is about the 'real' Python, it did come up in a websearch for 'Iron Python PYTHONPATH'. For Iron Python users as confused as I was: It turns out that Iron Python looks for an environment variable called IRONPYTHONPATH.
Linux/Mac/POSIX users: Don't forget that not only does Windows use \ as path separators, but it also uses ; as path delimiters, not :.
I have a directory which hosts all of my Django apps (C:\My_Projects). I want to add this directory to my PYTHONPATH so I can call the apps directly.
I tried adding C:\My_Projects\; to my Windows Path variable from the Windows GUI (My Computer > Properties > Advanced System Settings > Environment Variables). But it still doesn't read the coltrane module and generates this error:

Error: No module named coltrane