make safe obj_array_from_list to address issue #130 with test

pymdp/utils.py

@@ -259,7 +259,10 @@ def obj_array_from_list(list_input):
     """
     Takes a list of `numpy.ndarray` and converts them to a `numpy.ndarray` of `dtype = object`
     """
-    return np.array(list_input, dtype = object)
+    arr = obj_array(len(list_input))
+    for i, item in enumerate(list_input):
+        arr[i] = item
+    return arr
 
 def process_observation_seq(obs_seq, n_modalities, n_observations):
     """

test/test_utils.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+""" Agent Class
+
+__author__: Conor Heins, Alexander Tschantz, Daphne Demekas, Brennan Klein
+
+"""
+
+import unittest
+
+import numpy as np
+
+from pymdp import utils
+
+class TestUtils(unittest.TestCase):
+    def test_obj_array_from_list(self):
+        """
+        Tests `obj_array_from_list`
+        """
+        # make arrays with same leading dimensions. naive method trigger numpy broadcasting error.
+        arrs = [np.zeros((3, 6)), np.zeros((3, 4, 5))]
+        obs_arrs = utils.obj_array_from_list(arrs)
+
+        self.assertTrue(all([np.all(a == b) for a, b in zip(arrs, obs_arrs)]))
+
+if __name__ == "__main__":
+    unittest.main()