Python is not loaded for an engine mode MATLAB session

I'm starting MATLAB from a Python script by using the following commands:

import matlab.engine
eng = matlab.engine.start_matlab() # get MATLAB
eng.desktop(nargout=0)  # interactive MATLAB session

However, the started MATLAB session doesn't recognize Python commands. For example, pyversion returns

       version: ''
    executable: ''
       library: ''
          home: ''
      isloaded: 0

When MATLAB is started 'normally' (e.g. via its desktop shortcut), pyversion gives a meaningful output and it is possible to run Pythin commands in MATLAB.

The motivation to use Python in the MATLAB session started from Python is to convert the MATLAB output results to Python datatypes via py.list and similar commands. I.e. I don't want to get something like matlab.double back to Python.

While it is possible to circumvent this issue by smartly converting the MATLAB output to cells and then merging the resulting lists in Python, it would be interesting to clarify why Python is not accessible inside MATLAB in this particular case.

I'm trying to pass an n-by-2 matrix from MATLAB as a list of 2-tuples to Python (i.e. each matrix row should become a 2-tuple). Currently I'm doing the following:

col1 = num2cell(uint32(matr(:, 1)), 2);
col2 = num2cell(uint32(matr(:, 2)), 2);

And then in Python (cols is the output of the MATLAB function retrieved in Python):

col1 = cols[0]
col2 = cols[1]
lst = list(zip(col1, col2 ))

[Robert Snoeberger]

"The motivation to use Python in the MATLAB session started from Python is to convert the MATLAB output results to Python datatypes via py.list and similar commands. I.e. I don't want to get something like matlab.double back to Python."

This will not work the way you are expecting. If you look at the table "MATLAB Scalar Type to Python Type Mapping" [1], py.list will behave according to the row "MATLAB handle object," which means that you will get back a matlab.object.

[1] http://www.mathworks.com/help/matlab/matlab_external/handle-data-returned-from-matlab-to-python.html#bui0oph

[Ilya Tyuryukanov]

Thank you very much for this comment, then I'll resort to the second solution that I've mentioned, i.e. to convert the output to cell arrays and assemble them back in Python. I've updated the question to show what I'm currently doing.

Answer 1

[Robert Snoeberger]

Does this help?

import sys
eng.pyversion(sys.executable, nargout=0)

[Ilya Tyuryukanov]

eng.pyversion('C:\\Python34\\pythonw.exe', nargout=0) has helped indeed.