How do I call a MATLAB function in Python with the function output being a structure that contains a structure-array field?

I have written a MATLAB function which outputs a structure containing a field that is a structure array of more than 1 element. How can I call this function in Python using MATLAB Engine API?

Answer 1

[MathWorks Support Team]

You cannot call this type of MATLAB function in Python using Engine API because of the structure array in the function output. This is a known limitation as of R2019a.

Please run the below command in the command window of installed MATLAB R2019a version to get release specific documentation:

>> web(fullfile(docroot, 'matlab/matlab_external/handle-data-returned-from-matlab-to-python.html'))

As a workaround, you may consider converting the structure array to a row or column cell arrays of structures. Here is an example MATLAB function that works with Engine API:

function out = demo(x)
% create a scalar structure: 'st'
st.a = ones(2);
st.b = x;
out.st = st; % THIS WILL WORK with MATLAB Engine API

% % create a structure array: 'sta'
% sta(1).c = ones(2);
% sta(1).d = '1';
% sta(2).c = ones(3);
% sta(2).d = '2';
% out.sta = sta; % THIS WILL NOT WORK with MATLAB Engine API

% create a row cell array of scalar structures : 'sta'
st1.c = ones(2);
st1.d = '1';
st2.c = ones(3);
st2.d = '2';
sta = { st1, st2 };
out.sta = sta; % THIS WILL WORK with MATLAB Engine API

end

Please follow the below link to search for the required information regarding the current release:

https://www.mathworks.com/help/