added another test and error handling for passing empty lists into ch…

…oice functions.

concept_formation/tests/test_utils.py

@@ -21,6 +21,9 @@ def test_most_likely_choice():
     with pytest.raises(ValueError):
         utils.most_likely_choice([('a', -1)])
 
+    with pytest.raises(ValueError):
+        utils.most_likely_choice([])
+
 
 def test_weighted_choice():
     n = 1000
@@ -34,6 +37,9 @@ def test_weighted_choice():
     with pytest.raises(ValueError):
         utils.weighted_choice([('a', -1)])
 
+    with pytest.raises(ValueError):
+        utils.weighted_choice([])
+
 
 def test_cv_mean():
     for i in range(10):

concept_formation/utils.py

@@ -147,6 +147,7 @@ def weighted_choice(choices):
         if upto + w > r:
             return c
         upto += w
+    raise ValueError("Choices cannot be an empty list")
 
 
 def most_likely_choice(choices):
@@ -167,8 +168,12 @@ def most_likely_choice(choices):
     :return: the val with the hightest weight
     :rtype: val
     """
+    if len(choices) == 0:
+        raise ValueError("Choices cannot be an empty list")
+
     vals = [w for _, w in choices if w < 0]
     if len(vals) > 0:
         raise ValueError('All weights must be greater than or equal to 0')
+
     updated_choices = [(prob, random(), val) for val, prob in choices]
     return sorted(updated_choices, reverse=True)[0][2]