MATLAB: Call poly2trellis in Python

Question

Hi!

I want to call 'poly2trellis' from Python:

my_trellis = eng.poly2trellis(7, [133, 171])

This results in the following error:

Error using commstr2poly (line 180) Input must be a character vector or a cell of character vectors.

Error in poly2trellis (line 42) cellOutput = commstr2poly(codeGenerator, 'octal');

Thus, I did

function [ trellis ] = get_trellis( )
trellis = poly2trellis(7, [133 171]);
end

It works with all I want to do, but obviously I lost the ability to parameterize it. This is my next approach:

    function [ trellis ] = get_trellis( L_C )
    trellis = poly2trellis(L_C, [133 171]);
    end

This is called in Python with:

eng.get_trellis(7)

And it stops working with:

Error using poly2trellis_mex Input arguments must be nonempty real matrices.

Error in poly2trellis (line 51) trellis = poly2trellis_mex(varargin{:});

Error in get_trellis (line 4) trellis = poly2trellis(L_C, [133 171]);

The same function works if I call it in Matlab directly, but here I need MEfP, so this is not an option. Furthermore, I want to call 'poly2trellis' directly.

Any ideas how to make this work?

Thanks!

Answer 1

You need to use mlArray in order to pass an array to MATLAB from Python. A Python list is converted into a MATLAB Cell array which is not accepted by "poly2trellis". Try this:

 >>> eng.poly2trellis(7.0, matlab.double([133,171]))

Reference:

http://www.mathworks.com/help/matlab/matlab_external/use-matlab-arrays-in-python.html