How to call MATLAB library from Python virtual environment on Mac

Question

I am trying to call a MATLAB package packaged for Python on macOS from a virtual environment.

In order to use the MATLAB runtime on macOS, the DYLD_LIBRARY_PATH must be updated to point to the MATLAB Runtime as well as libpython3.6.dylib.

export DYLD_LIBRARY_PATH="/Applications/MATLAB/MATLAB_Runtime/v95/runtime/maci64:/Applications/MATLAB/MATLAB_Runtime/v95/sys/os/maci64:/Applications/MATLAB/MATLAB_Runtime/v95/bin/maci64:/Library/Frameworks/Python.framework/Versions/3.6/lib:${DYLD_LIBRARY_PATH}"

Then create and activate a Python virtual environment:

$ python3.6 -m venv py36
$ source py36/bin/activate

Next install the MATLAB packaged for Python application into the virtual environment:

(py36) $ cd /Applications/my_matlab_app/application
(py36) $ python setup.py install
(py36) $ pip list
Package                Version
---------------------- -------
matlabruntimeforpython R2018b 
pip                    18.1   
setuptools             40.6.2 

Now attempt to run a script that imports your MATLAB library within the virtual environment:

(py36) $ python matlab_test.py 
Exception caught during initialization of Python interface. Details: On the Mac, use 'mwpython' rather than 'python' to start a script or session that will call deployed MATLAB code from Python.
Traceback (most recent call last):
  File "matlab_test.py", line 26, in <module>
    import my_matlab_app
  File "/Users/user/venv/py36/lib/python3.6/site-packages/my_matlab_app/__init__.py", line 283, in <module>
    _pir.import_cppext()
  File "/Users/user/venv/py36/lib/python3.6/site-packages/my_matlab_app/__init__.py", line 276, in import_cppext
    self.cppext_handle = importlib.import_module("matlabruntimeforpython" + self.interpreter_version)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
RuntimeError: On the Mac, use 'mwpython' rather than 'python' to start a script or session that will call deployed MATLAB code from Python.

The problem is that as far as I can tell, mwpython can't be used within virtual environments. Is there a way to work around this? We're currently struggling making repeatable environments because mwpython seems to hard code everything to be globally installed.

Tested on:

• macOS 10.14.2
• Python 3.6.8 installed from python.org
• MATLAB Runtime 2018b

Answer 1

The activate script unsets PYTHONHOME and sets VIRTUAL_ENV, which is the folder path to your virtual environment. mwpython will use the python interpreter pointed to by PYTHONHOME (assuming it is a supported version, of course). So, you merely need to set and export PYTHONHOME to VIRTUAL_ENV before calling mwpython, e.g.

python3.6 -m venv py36
source py36/bin/activate

export PYTHONHOME=$VIRTUAL_ENV
mwpython matlab_test.py