Enable 3rd-party packages in Blender using virtualenv

blender_venv.org

Install external python packages + virtualenv with Blender

Requirements: Blender 2.80+ (2.79 should also work with pip method, not tested thoroughly)

Step 1: Install virtualenv on the system

In order not to mix the packages installed for Blender (such as scipy, matplotlib) with those system-wide packages, we need to create a virtual environment for the Blender alone.

Best practice is to use a single virtualenv for each version of Blender. See the following steps:

• Find the python binary bundled with Blender, for example (/Applications/Blender/blender.app/Contents/Resources/2.79/python/bin/python3.5m, for version 2.79 on macOS)
• Create a virtual environment under the desired location, like:

  # Need the following if Blender < 2.80
  /path/to/blender/bin/python -m ensurepip
  # Replace the path according to your system
  /path/to/blender/bin/python -m pip /path/to/virtualenv
      

• Activate the virtual environment and install 3rd packages using pip

  # Replace the path and package name according to your system
  # For Windows system the path is under \path\to\virtualenv\Scripts\activate
  source /path/to/virtualenv/bin/activate
  python -m pip install 3rd-party-packages
      

Step 2: Modify the init script of virtual environment

The packages installed under the virtual environment needs to be found by the Blender-bundled python, which is done by modifying the PYTHONPATH environment variable.

Add the following line at the end of the activate script (/path/to/virtualenv/bin/activate):

export PYTHONPATH=$VIRTUAL_ENV/lib/pythonX.Y/site-packages/

Note the actual path may be different if you are using Windows. See comments below.

Reactivate the python vitrualenv will make the Blender-bundled python detect the 3rd-party package. Test this with a short script (for example named as test.py and the package is ase):

import sys
import bpy
print("Path to search python libraries", sys.path)
print("Python path is: ", bpy.__path__)

try:
    import ase
    print("ASE library in ", ase.__path__)
except ImportError:
    print("ASE not installed!")

Test this script with:

/path/to/blender -b -p test.py

Actually, another way to do it without modifying the activate script is to add this to your top-level python code:

# Activate current virtualenv -- needed to get additional modules
# This updates sys.path, sys.prefix and maybe other things.
activate_this = os.path.join(os.environ['VIRTUAL_ENV'], 'Scripts/activate_this.py')
if not os.path.exists(activate_this):
    activate_this = os.path.join(os.environ['VIRTUAL_ENV'], 'bin/activate_this.py')
if os.path.exists(activate_this):
    logger.info(f'Activating virtualenv: {os.path.basename(os.environ["VIRTUAL_ENV"])}')
    exec(open(activate_this).read(), {'__file__': activate_this})
else:
    logger.warn(f'WARNING: no activate_this: {activate_this}')
    sys.exit(1)

You still have to run blender -b --python from an activated virtualenv (i.e. VIRTUAL_ENV must be set), but at least it's one less step per virtualenv.

A couple of notes for others using this method:

I'm using blender 2.81 prerelease (bundles python 3.7.4) on Windows 10, and had to do this to create a working virtualenv:

$BLENDERTOP/2.81/python/bin/python -mpip install virtualenv
$BLENDERTOP/2.81/python/bin/python -mvirtualenv /path/to/virtualenv

Also, I'm on Windows, so my activate is in $VIRTUAL_ENV/Scripts/activate

And one more thing: I had to set PYTHONPATH to export PYTHONPATH=$VIRTUAL_ENV/Lib/site-packages.

But once I have that straightened out and activate the virtualenv, I can do pip install and blender -b --python foo.py and it finds my modules. Now if only python foo.py would work in the virtualenv! But this is workable.

Thanks for the comments and suggestion. I haven't used virtualenv on Windows yet so I'll just add your solutions to the gist.

Concerning the python scripts, your solution is nice!

For those coming across this, you might find that the answer https://blender.stackexchange.com/a/132279 gives you what you want (even if it isn't a proper virtualenv).

Hey,
I am trying to get this to work for Blender 2.93 on a windows machine with anaconda and tried the following steps:

1. activate virtual_env
2. cd /path/to/blender/bin/
3. python -mpip install virtualenv
4. python -mvirtualenv /path/to/virtualenv
5. editing activate script of virtual environment - inserting export PYTHONPATH=$VIRTUAL_ENV/Lib/site-packages

but when I now try to activate the virtual env and pip install something it throws me an error: No python at /path/to/blender/python.exe.
Does anyone else have the same problem?