Python Matlab engine - Cannot read simulink output

I'm trying to read the output of a Simulink simulation through Python with Matlab Engine but I'm having trouble as I am not able to get the output data.

I've seen this post : https://www.mathworks.com/matlabcentral/answers/725147-data-from-simulink-to-python-with-to-workspace-block?s_tid=answers_rc1-1_p1_Topic

But it doesn't work for me.

calling sim() does not add the output to the workspace and the object it returns has no usable properties (except size)

Python 3.6.4. Matlab 2020b

Thank you

import matlab
import matlab.engine as matlabEngine
import math
import numpy as np
import time


class LogTime:
   def __init__(self, action):
      self.action = action

   def __enter__(self):
      print('%s...' % self.action, end='', flush=True)
      self.time_start = time.time()

   def __exit__(self, *args, **kwargs):
      print('Done in %0.3f seconds' % (time.time()-self.time_start))

# Params
modelname = 'simpleModel'
stopTime = 1;
nbPoints = 10000;
simstep = 0.0001;


with LogTime('Starting Matlab Engine'):
   m = matlabEngine.start_matlab();

t = np.linspace(0,stopTime,nbPoints)
voltage = 120*math.sqrt(2)*np.sin(2*math.pi*60*t)
current = 120*math.sqrt(2)*np.sin(2*math.pi*60*t + math.pi/8)

# Numpy to matlab conversion
t = matlab.double(t.tolist())
voltage = matlab.double(voltage.tolist())
current = matlab.double(current.tolist())

# Write to workspace for model
m.workspace['input_voltage'] = m.timeseries(voltage, t)
m.workspace['input_current'] = m.timeseries(current, t)

with LogTime('Loading Model'):
   m.load_system(modelname, nargout=0)

m.set_param(modelname, 'StopTime', str(stopTime), 'FixedStep', str(simstep), nargout=0)

with LogTime('Running simulation'):
   out = m.sim(modelname)  # Empty object. don't know what to do with it.

Answer 1

[Pier-Yves Lessard]

I finally made it work.

the object return by sim() is a SimulationOutput object and it can be access by calling its method and passing the object as first parameter.

m.get(out, '<signalName>')

This worked

ts = m.get(out, 'power')
out_data = m.transpose(m.get(ts, 'Data')[0])
out_time = m.get(ts, 'Time')

t2 = np.array(out_time)
power = np.array(out_data)

from matplotlib import pyplot as plt
plt.plot(t2, power)
plt.show()

input('Press any key...')

Answer 2

[Sean de Wolski]

Extract the simout to a timetable, then pass the timetable back to python either via writing to disk as a CSV, or converting to a struct (timetable2table(table2struct()) directly back to python.