Using Python with the MATLAB engine, how can I supress the warning

I'm using Python to fetch some block's mask parameter. Those parameter are string with no evaluation of value needed.

Every time I try to load the model, I receive those warning:

Warning: Error evaluating 'PreLoadFcn' callback of block_diagram 'LibraryTest'.

Callback string is 'LibraryTest_init;'

> In load_system>i_load_system (line 44)

In load_system (line 20)

Warning: Unrecognized function or variable 'LibraryTest_init'.

> In load_system>i_load_system (line 44)

The Python script is not in the model folder, as such, those warning are expected as the init file is with the model.

Is there a way to just supress those warning in python so that they don't print?

Answer from Broy

[Ram Prasanth]

Hello @Eric Laurendeau

If the warnings are in the Matlab Command Window. You can use this below warnings off command to supress it.

Suppress Warnings - MATLAB & Simulink

[Eric Laurendeau]

The warning are in the python script console. When I try to turn off the warning, I have an error:

only a scalar struct can be returned from MATLAB

When trying to turn off all warning.

My code look like this:

eng = matlab.engine.start_matlab()
try:
    WarningStatus = eng.warning             # <matlab.engine.matlabengine.MatlabFunc object>
    eng.warning('off', 'all')               # To turn off all warning
    eng.load_system(ModelPath, nargout=0)   # Open the wanted model. That's where I want to suppress the warning
    
    [ DO STUFF ]
    
finally:
    eng.warning(WarningStatus)              # Restore warning
    eng.quit()                              # Close the engine

[Broy]

Use nargout = 0 to explicitly tell Python not to expect a return value.

eng = matlab.engine.start_matlab()

try:
    % 1. Save the current warning state directly into the MATLAB workspace.    
    eng.eval("previousState = warning;", nargout=0) 
    % 2. Turn off warnings.    
    eng.warning('off', 'all', nargout=0)
    
    % Rest of the Code
finally:
    % 3. Restore the warning state
    if eng.workspace.get('previousState'):
        eng.eval("warning(previousState);", nargout=0)
        
    % Rest of the Code

[Eric Laurendeau]

Thanks you! That fixed the problem. The only problem left is that the line

if eng.workspace.get('previousState'):

give the error: 'MatlabWorkSpace' object has no attribute 'get'

I tried:

if eng.workspace.get('previousState'): % Give the error: 'MatlabWorkSpace' object has no attribute 'get'

if "previousState" in eng.worspace: % Give the error: Variable name must be string, not int

if eng.exist('previousState', 'var'): % Still print some information. If set with nargout = 0, return nothing so not usefull

if eng.workspace["previousState"] != []: % Give the error: only a scalar struct can be returned from MATLAB

So I simply used the basic try/except:

try:

eng.eval("warning(previousState);", nargout=0)

except e:

warnings.warn(f"Error while restoring the previous warning state: \n{e}")

Considering that it is in the same script and same function, if the variable does not exist, there is another problem.