Why am I getting 'MatlabExecutionError: Too many output arguments.' when using the Matlab engine in Python?

Here is the code I am running on each side:

Python

>>> m1 = matlab.engine.start_matlab()
>>> testpath = 'Path/to/file/containing-testfunc.m'
>>> m1.addpath(testpath)
*lots of path gibberish*
>>> m1.testfunc()
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "/Library/Python/2.7/site-packages/matlab/engine/matlabengine.py"
, line 79, in __call__
    _stderr).result()
  File "/Library/Python/2.7/site-packages/matlab/engine/futureresult.py"
, line 107, in result
    self._future,self._nargout, None, out=self._out, err=self._err)
MatlabExecutionError: Too many output arguments.

I have double checked the path to testfunc.m, and I suspect that Matlab is able to find it because otherwise it would say it could not find it.

Here are the contents of testfunc.m:

function [] = testfunc()
    a = 2
end

As indicated by the name, this function is only a test because I found this error using a more complicated function. I created the testfunc() just to try to narrow down the reasons for which I might be getting this error. I am able to run testfunc() (and my more complicated function) from the Matlab gui if I use

Python

>>> m1.desktop(nargout=0)

Matlab

>> testfunc()

a =

     2

This leads me to believe there is an issue with the Matlab engine or the way I am using it.

It might be important to point out that built in Matlab functions seem to be working fine in the engine for example:

m1.workspace['testvar'] = 10

I am only having trouble using functions that I include myself.

Any help would be greatly appreciated.

[Richard McEver]

I have found the issue after a little reading; however, I'll go ahead and post it here in case anyone has similar troubles. It was necessary to specify nargout=0 as an argument to testfunc() i.e.

testfunc(nargout=0)

[Yehonatan Peleg]

Thanks...

[rui gao]

Thanks, it works.

We can also put some input parameters before the 'nargout=0' for the situation that the function need some input.

For example:

eng = matlab.engine.start_matlab()

eng.MatlabFunctionName(1, 2, 3, nargout=0)

eng.quit()

[Nagabhushan SN]

Thanks! very useful. Is it possible to upvote a comment here? Like in SO

Answer 1

[Bo Li]

Try this:

 >>>m1.testfunc(nargout=0)

By default, the nargout is set to 1 in Python Engine:

<http://www.mathworks.com/help/matlab/apiref/matlab.engine.matlabengine-class.html?searchHighlight=python%20engine>

Since testfunc.m does not return any result, you need to specify nargout to be 0 like what you did to launch the MATLAB Desktop:

 >>>m1.desktop(nargout=0)

[Richard McEver]

Thanks so much that solved it!

[Bogdan -Ervin]

How can I use disp method of a Matlab class in Python?

Answer 2

[Khaoula Mosbahi]

hello everyone , i need your help , when i run matlab code en matlab i found this result

but when i try this code:

eng = matlab.engine.start_matlab()

kh=eng.Main(7, nargout=0)

print(kh)

the result always NONE

help please