No module named 'PIL'

I'm running into an error where when I try

from PIL import Image, ImageFilter

in a Python file I get an error stating ModuleNotFoundError: No module named 'PIL'.

So far I've tried uninstalling/reinstalling both PIL and Pillow, along with just doing import Image, but the error keeps on occurring and I have no idea why. All the solutions I've found so far have had no effect on my issue.

I'm running Python 3.5 on Ubuntu 16.04