[matlab-to-python binding] How to pass a dictionary from matlab to python ? And loop over keys/values in python ?

Hi,

I am using the matlab-to-python binding (python setup.py install in <matlabroot>/extern/engines/python).

How to pass a dictionary from matlab to python ? And loop over keys/values in python ?

In matlab I have a doStuff.m file which looks like:

function dict = doStuff()
  k = strings(2, 1);
  v = zeros(2, 1);

  for i = 1:2
      v(i) = i;
      k(i) = ['key', num2str(i)];
  end

  dict = containers.Map(k, v);
end

In python I have a doStuff.py file which looks like:

import matlab.engine
eng = matlab.engine.start_matlab()
dict = eng.doStuff()
for k in dict:
    print(k, dict[k])

And finally get error of this kind in python (after matlab ran OK):

    $ python doStuff.py
    Traceback (most recent call last):
      File "doStuff.py", line 5, in <module>
        print(k, dict[k])
    TypeError: sequence index must be integer, not 'matlab.object'

If this way to go could hit a limitation: is there any workaround ?

FH

Answer 1

[Franck HOUSSEN]

Found a workaround: convert dict to string, and, pass string from matlab to python. For people who want to know:

$ cat doThing.m
function kv = doThing()
  k = strings(2, 1);
  v = zeros(2, 1);

  for i = 1:2
      v(i) = i;
      k(i) = ['key', num2str(i)];
  end

  dict = containers.Map(k, v);

  kv = [keys(dict); values(dict)];
  kv = sprintf('%s=%.1f ', kv{:});
end

$ cat doThing.py
import matlab.engine
eng = matlab.engine.start_matlab()
kv = eng.doThing()
for token in kv.split():
    k = token.split('=')[0]
    v = token.split('=')[1]
    print(k, v)

$ python doThing.py
key1 1.0
key2 2.0