Some Googling Stackoverflow provided me with the following approach:
- create a (temporary) virtual environment (VE) linking against Blender's python executable
- within that VE, pip install the packages you need, but into a folder in Blender's Python path (e.g. the one in ~/.config)
- I'd keep the VE, but Blender doesn't need it to be active to run.
In code (I keep Blender in ~/.local/bin, adapt to your setup), for matplotlib (You might have to run blender once at first to create the file structure in .config):
virtualenv --python=~/.local/bin/blender-2.81a/2.81/python/bin/python3.7m ve-blender
source ve-blender/bin/activate
mkdir -p ~/.config/blender/2.81/scripts/modules/
pip install --upgrade -t ~/.config/blender/2.81/scripts/modules/ matplotlib
deactivate
Run Blender.
Update: When I tried to do this with pickle5, gcc failed via "Python.h: No such file or directory".
Fix: within the active VE, determine the Blender Python version (python -V).
Download the respective sources (e.g. 3.7.7) from www.python.org. and unpack.
Copy the contents of the Include directory to ~/.local/bin/blender-2.81/2.81/python/include/python3.7m/ (adapt versions and paths).
Next update:
Broken pip after initializing the virtual environment. Fixable via pip's bootstrap installer:
curl -sS https://bootstrap.pypa.io/get-pip.py | python3
Sources:
https://stackoverflow.com/questions/1534210/use-different-python-version-with-virtualenv
https://blender.stackexchange.com/questions/132278/how-to-make-use-of-custom-external-python-modules-in-blender-or-an-add-on-on-lin
https://blender.stackexchange.com/questions/81740/python-h-missing-in-blender-python
