I am trying to add a path to the PYTHONPATH environment variable, that would be only visible from a particular virtualenv environment.
I tried SET PYTHONPATH=
SET PYTHONPATH=
If you are using virtualenvwrapper,
$ cd to the parent folder $ add2virtualenv folder_to_add
console will display
Warning: Converting "folder_to_add" to "/absoutle/path/to/folder_to_add"
That's it, and you should be good to go