diff --git a/Python/ml_metrics/average_precision.py b/Python/ml_metrics/average_precision.py
index e18297d..c735735 100644
--- a/Python/ml_metrics/average_precision.py
+++ b/Python/ml_metrics/average_precision.py
@@ -22,6 +22,12 @@ def apk(actual, predicted, k=10):
             The average precision at k over the input lists
 
     """
+    if actual is None or len(actual) == 0:
+        return 0.0
+
+    if predicted is None or len(predicted) == 0:
+        return 0.0
+
     if len(predicted)>k:
         predicted = predicted[:k]
 
@@ -33,9 +39,6 @@ def apk(actual, predicted, k=10):
             num_hits += 1.0
             score += num_hits / (i+1.0)
 
-    if not actual:
-        return 0.0
-
     return score / min(len(actual), k)
 
 def mapk(actual, predicted, k=10):
@@ -48,7 +51,7 @@ def mapk(actual, predicted, k=10):
     Parameters
     ----------
     actual : list
-             A list of lists of elements that are to be predicted 
+             A list of lists of elements that are to be predicted
              (order doesn't matter in the lists)
     predicted : list
                 A list of lists of predicted elements
diff --git a/Python/ml_metrics/test/test_average_precision.py b/Python/ml_metrics/test/test_average_precision.py
index d1cf761..2af7b57 100644
--- a/Python/ml_metrics/test/test_average_precision.py
+++ b/Python/ml_metrics/test/test_average_precision.py
@@ -9,9 +9,20 @@ class TestAveragePrecision(unittest.TestCase):
     def test_apk(self):
         self.assertAlmostEqual(metrics.apk(range(1,6),[6,4,7,1,2], 2), 0.25)
         self.assertAlmostEqual(metrics.apk(range(1,6),[1,1,1,1,1], 5), 0.2)
-        predicted = range(1,21)
+        predicted = list(range(1,21))
         predicted.extend(range(200,600))
         self.assertAlmostEqual(metrics.apk(range(1,100),predicted, 20), 1.0)
+        # numpy array test
+        self.assertAlmostEqual(metrics.apk(np.asarray(range(1,100)),predicted, 20), 1.0)
+        self.assertAlmostEqual(metrics.apk(range(1,100), np.asarray(predicted), 20), 1.0)
+
+
+    def test_apk_empties(self):
+        self.assertAlmostEqual(metrics.apk([], [1, 3], 20), 0.0)
+        self.assertAlmostEqual(metrics.apk(None, [1, 2], 20), 0.0)
+        self.assertAlmostEqual(metrics.apk([1, 3], [], 20), 0.0)
+        self.assertAlmostEqual(metrics.apk([1, 2], None, 20), 0.0)
+
 
     def test_mapk(self):
         self.assertAlmostEqual(metrics.mapk([range(1,5)],[range(1,5)],3), 1.0)