Find the directory that Python searchers for path additions:
python -c 'import site; site._script()' --user-site
In my case, it was:
~/Library/Python/2.7/lib/python/site-packages
Create a text file there with an extension “.pth” and add directories. My file looks something like:
~/Library/Python/2.7/lib/python/site-packages/mc_custom.pth:
# Custom additions on 5/27/16
/Users/mclaffey/Documents/my_modules