Transform a Dict (or any python data structure) to Struct or Cell Array in Matlab.

Hi,

I'd like to create a structure or a cell array from Matlab given a Python dictionary. I'm using the built-in Python API to call from Matlab a user-defined function I wrote in Python.

The function I wrote (saved in a file called 'py2mat.py') is like this:

def test(w,j,l):
    array1 = np.array([w,j,l])
    array2 = np.array(['a','b','c'])
    array3 = np.array([1.01,2.02,3.03])
    df = pd.DataFrame({'array1':array1, 'array2':array2,'array3':array3})
    return df.to_dict()

To call in Matlab, I do this:

N=py.py2mat.test(2,4,5);
s=struct(N);

And everything's great, but... when I look into the struct, all I got is this data structure with nested dictionaries. So, how do I do to display the values of the dictionaries into struct fields or cell arrays for further manipulation?

I'd like to know.

Thanks a lot for your time!

Answer 1

[Ajpaezm]

I wrote a small function that transforms the dictionary into a cell array and then that cell array is used to populate a structure. Same principle can be applied to other python dictionaries. Hope this somehow works for anyone else working with Matlab and Python.

function new_s=my_py2mat(a,b,c)
n=py.py2mat.test(a,b,c);
s=struct(n);
field_list=fieldnames(s);
rows=double(py.len(s.(field_list{1}))); %size and numel can't acquire the dimension of a python dictionary, that's why we call py.len()
new_array=cell(rows,numel(field_list));
for i=1:numel(field_list)
    temp=s.(field_list{i});
    for j=1:rows
        if isa(temp{j-1},'py.str')
            new_array{j,i}=char(temp{j-1});
        elseif isa(temp{j-1},'py.int')
            new_array{j,i}=double(temp{j-1});
        else 
            new_array{j,i}=temp{j-1};
        end
    end
     s.(field_list{i})=new_array(:,i);
end
new_s=s;