To be able to import python libraries, it seems to work to add a path to where the python libraries are on disk in the
Project Settings> General> Filesystem> Python Script> Path using the Godot editor.
I'm using conda, and I've added
which seems to make packages such as math, numpy, etc importable in Godot. The file references are on Ubuntu linux.
To find where your python libraries are, open a python shell and do:
which should give you the paths that your python installation uses to locate python libraries for import.
You can also import your own python modules by adding them to the project folder. Just make sure that
res:// or any other local Godot file reference exists in the
Project Settings> General> Filesystem> Python Script> Path in the Godot Editor.