BUG: Correct length_of_indexer for range objects

pandas/core/indexers/utils.py

@@ -325,7 +325,7 @@ def length_of_indexer(indexer, target=None) -> int:
             return indexer.sum()
         return len(indexer)
     elif isinstance(indexer, range):
-        return (indexer.stop - indexer.start) // indexer.step
+        return len(indexer)
     elif not is_list_like_indexer(indexer):
         return 1
     raise AssertionError("cannot find the length of the indexer")

pandas/tests/indexing/test_indexers.py

@@ -16,6 +16,11 @@ def test_length_of_indexer():
     assert result == 1
 
 
+def test_length_of_indexer_range():
+    indexer = range(0, 5, 2)
+    assert length_of_indexer(indexer) == len(indexer)
+
+
 def test_is_scalar_indexer():
     indexer = (0, 1)
     assert is_scalar_indexer(indexer, 2)