Calling MATLAB class functions from Python with matlab.engine

I have a MATLAB MPC (PU_SMPC) class that I can properly initialize within Python with the matlab.engine API by running:

import matlab.engine
eng = matlab.engine.start_matlab()
smpc = eng.PU_SMPC(params, nargout=1)

which returns a matlab.object. However, I cannot figure out how to run the PU_SMPC method simulation, which takes an integer as an input. Here's a summary of what I have tried and the errors I get:

smpc.simulation(60)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
AttributeError: 'matlab.object' object has no attribute 'simulation'

,

eng.simulation(smpc, 60)
Error using PU_SMPC/simulation
Too many output arguments.
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\matlabengine.py", line 70, in __call__
    return FutureResult(self._engine(), future, nargs, _stdout,
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\futureresult.py", line 67, in result
    return self.__future.result(timeout)
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: Too many output arguments.

,

eng.simulation(60)
Undefined function 'simulation' for input arguments of type 'int64'.
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\matlabengine.py", line 70, in __call__
    return FutureResult(self._engine(), future, nargs, _stdout,
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\futureresult.py", line 67, in result
    return self.__future.result(timeout)
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: Undefined function 'simulation' for input arguments of type 'int64'.
end

,

eng.PU_SMPC.simulation(60)
Unrecognized function or variable 'PU_SMPC.simulation'.
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\matlabengine.py", line 70, in __call__
    return FutureResult(self._engine(), future, nargs, _stdout,
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\futureresult.py", line 67, in result
    return self.__future.result(timeout)
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: Undefined function 'PU_SMPC.simulation' for input arguments of type 'int64'.
end

,

eng.PU_SMPC.simulation(smpc, 60)
Unrecognized function or variable 'PU_SMPC.simulation'.
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\matlabengine.py", line 70, in __call__
    return FutureResult(self._engine(), future, nargs, _stdout,
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\futureresult.py", line 67, in result
    return self.__future.result(timeout)
  File "C:\Users\Usuario\PycharmProjects\Adaptive_SMPC\matlab\engine\fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: Undefined function 'PU_SMPC.simulation' for input arguments of type 'PU_SMPC'.
end

I cannot access any of the class member from Python.

Here's a sample of what the class looks like:

classdef PU_SMPC < handle
    properties
        A;
        B;
        C;
    end
    methods
        function obj = PU_SMPC(A,B,C)
            A = A;
            B = B;
            C = C;
        end
        function simulation(obj, simulation_time)
            %code to run simulation
        end
    end

Any suggestions?

Answer 1

[Sean de Wolski]

MWE works for me. Specify nargout, and make sure your directories are on the path (strongly recommend using Projects for this, i.e. openProject() being the first thing you do in python engine so that the entire MATLAB is setup for what you're working on)

Answer 2

[Yongjian Feng]

You first need to instantiate a PU_SMPC object in python, right? You are calling the member method simulation as a static method.

[Javier Perez Tobia]

Isn't smpc the PU_SMPC object?

[Yongjian Feng]

I see. It seems like the second way is close to success. The only thing missing is that pythonengine expects simulation to return something.

Can you modify your simulation method to return an integer. And then repeate second way:

eng.simulation(smpc, 60);

[Indhu Priyadharshini Govindasamy]

Hello @Yongjian Feng,

I am trying to call matlab workspace variable in python using matlab engine API

method one

eng.eval('a = simout;',nargout=0)

eng.eval('b = tout;',nargout=0)

mpi = eng.workspace['a']

ki=eng.workspace['b']

method two

mpi = eng.workspace['simout']

ki=eng.workspace['tout']

i used these lines of code

i can get simout values in python but for tout i am getting this error

matlab.engine.MatlabExecutionError: Unrecognized function or variable 'tout'.

could you please help me to fix this?