It’s also worth noting that we enabled python site-packages/ in Ignition 8. (Ignition/user-lib/pylib/site-packages)
What this means is that you can drop libraries in there to make them available in Ignition.
You can also use pypi / pip by doing the following:
Follow the Using pip section in the linked document here. Python, Jython, CPython, Libraries, Pip, and Python 2.7 vs 3 - A quick primer
As others have mentioned, this doesn’t work for CPython specific packages that have native dependencies, but it does work for a whole slew of utility, parsing, and web libraries (things like AWS client libraries).
[Edited to reference the guidance doc with updated instructions.]