Passing path as input argument in matlab.engine

I'm using the following lines of code to run main.m (I:/xxx/simcode/xxx/main) with path as input argument, using matlabe engine

import matlab.engine
eng = matlab.engine.start_matlab()
eng.run("I:/xxx/simcode/xxx/main, ['I:/xxx/xxxx/xxx/task5'])
eng.quit()

But I get an error,

self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)

matlab.engine.MatlabExecutionError: Too many input arguments.

Could someone please suggest how to fix this?

I would like to run the main.m from python by passing an input argument which is a path.

[Deepa Maheshvare]

Any suggestions?

Answer 1

[Steven Lord]

The run function in MATLAB accepts only one input, the name of a script file. Is your main.m a script file or a function file? If the former it cannot accept input arguments; that's one of the defining characteristics of a script! If it's a function file, I think you can run it directly with something like (untested)

import matlab.engine
eng = matlab.engine.start_matlab()
eng.main("['I:/xxx/xxxx/xxx/task5']")
eng.quit()

Or if you need to change directories before calling your function, call cd then call feval in your MATLAB Engine session.

Note that I haven't used this functionality directly, I'm just going by what I see in the documentation.

[Deepa Maheshvare]

Thanks a lot.

I tried,

import matlab.engine
eng = matlab.engine.start_matlab()
eng.main("['I:/xxx/xxxx/xxx/task5']")
eng.quit()

and unfortunately, I get the following error.

File "C:\Users\xxx\anaconda3\envs\xxxx\lib\site-packages\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.

I tried,

r =

eng.main("['I:/xxx/xxxx/xxx/task5']")

and I still get the same error.

main.m is a function which takes input argument TASK_DIR (path to a excel file) and it doesn't return any value.

function main(TASK_DIR)

To change to the directory in which main.m is saved, I was using

os.chdir(SIMULATOR_DIR)

Now, I have changed to

eng = matlab.engine.start_matlab()
eng.cd("I:/xxx/xxxx/factory", nargout=0)
eng.main(["I:/xxx/xxxx/xxx/task5"])
eng.quit()

for some reason I get the same error as reported above ( Too many output arguments).

I am not sure if nargot=0 is passed in the right place.

Could you please have a look? And could you also show an small example on how to use

`feval ` or `eval`? Can we use `nargout` in feval/eval?

[Steven Lord]

Try:

eng = matlab.engine.start_matlab()
eng.cd("I:/xxx/xxxx/factory", nargout=0)
eng.main(["I:/xxx/xxxx/xxx/task5"], nargout=0)
eng.quit()

[Deepa Maheshvare]

Thanks so much!

I don't get the error now.

If I may ask one last question,

There is minor issue :

main.m is present in I:/xxx/xxxx/factory

and main.m accesses a method in class io_utils which is in I:/xxx/xxxx/utils.

When running main.m in gui, I include all the subfolders in I:/xxx/xxxx/ to path.

However, I am not sure how to do the same while running from python.

I get the following error, I think the path to io_utils class is not recognized.

File I:\xxx\xxxx\factory\main.m, line 16, in main
Unable to resolve the name 'io_utils.get_task'.

Could you please suggest how the subfolders can be added to path?

Thanks a lot

[Deepa Maheshvare]

I think I should be using eng.addpath('/path/to/subfolder').