Fix remainder logic for subset splitting (#1222)

datumaro/datumaro/plugins/transforms.py

@@ -325,8 +325,12 @@ class RandomSplit(Transform, CliPlugin):
     def __init__(self, extractor, splits, seed=None):
         super().__init__(extractor)
 
-        total_ratio = sum((s[1] for s in splits), 0)
-        if not total_ratio == 1:
+        assert 0 < len(splits), "Expected at least one split"
+        assert all(0.0 <= r and r <= 1.0 for _, r in splits), \
+            "Ratios are expected to be in the range [0; 1], but got %s" % splits
+
+        total_ratio = sum(s[1] for s in splits)
+        if not abs(total_ratio - 1.0) <= 1e-7:
             raise Exception(
                 "Sum of ratios is expected to be 1, got %s, which is %s" %
                 (splits, total_ratio))
@@ -336,7 +340,6 @@ class RandomSplit(Transform, CliPlugin):
 
         random.seed(seed)
         random.shuffle(indices)
-
         parts = []
         s = 0
         for subset, ratio in splits:
@@ -350,7 +353,7 @@ class RandomSplit(Transform, CliPlugin):
         for boundary, subset in self._parts:
             if index < boundary:
                 return subset
-        return subset
+        return subset # all the possible remainder goes to the last split
 
     def __iter__(self):
         for i, item in enumerate(self._extractor):

datumaro/tests/test_project.py

@@ -534,15 +534,10 @@ class DatasetTest(TestCase):
 
 class DatasetItemTest(TestCase):
     def test_ctor_requires_id(self):
-        has_error = False
-        try:
+        with self.assertRaises(Exception):
             # pylint: disable=no-value-for-parameter
             DatasetItem()
             # pylint: enable=no-value-for-parameter
-        except AssertionError:
-            has_error = True
-
-        self.assertTrue(has_error)
 
     @staticmethod
     def test_ctors_with_image():

datumaro/tests/test_transforms.py

@@ -342,18 +342,22 @@ class TransformsTest(TestCase):
         self.assertEqual(4, len(actual.get_subset('train')))
         self.assertEqual(3, len(actual.get_subset('test')))
 
-    def test_random_split_gives_error_on_non1_ratios(self):
+    def test_random_split_gives_error_on_wrong_ratios(self):
         class SrcExtractor(Extractor):
             def __iter__(self):
                 return iter([DatasetItem(id=1)])
 
-        has_error = False
-        try:
+        with self.assertRaises(Exception):
             transforms.RandomSplit(SrcExtractor(), splits=[
                 ('train', 0.5),
                 ('test', 0.7),
             ])
-        except Exception:
-            has_error = True
 
-        self.assertTrue(has_error)
+        with self.assertRaises(Exception):
+            transforms.RandomSplit(SrcExtractor(), splits=[])
+
+        with self.assertRaises(Exception):
+            transforms.RandomSplit(SrcExtractor(), splits=[
+                ('train', -0.5),
+                ('test', 1.5),
+            ])