[Datasets] Raise error message if user calls Dataset.__iter__ (ray-…

…project#30575) New users might try for item in dataset and get confused when they receive the default error message. This PR adds a more descriptive error that points users towards Dataset.take or Dataset.map_batches. Signed-off-by: tmynn <[email protected]>
ju2ez · Jan 25, 2023 · 133e4d1 · 133e4d1
1 parent 81a1032
commit 133e4d1
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/python/ray/data/dataset.py b/python/ray/data/dataset.py
@@ -4206,6 +4206,13 @@ def __len__(self) -> int:
             "This may be an expensive operation."
         )
 
+    def __iter__(self):
+        raise TypeError(
+            "`Dataset` objects aren't iterable. To iterate records, call "
+            "`ds.iter_rows()` or `ds.iter_batches()`. For more information, read "
+            "https://docs.ray.io/en/latest/data/consuming-datasets.html."
+        )
+
     def _block_num_rows(self) -> List[int]:
         get_num_rows = cached_remote_fn(_get_num_rows)
         return ray.get([get_num_rows.remote(b) for b in self.get_internal_block_refs()])