fixup put

src/zarr/core/attributes.py

@@ -37,7 +37,17 @@ def __len__(self) -> int:
         return len(self._obj.metadata.attributes)
 
     def put(self, d: Mapping[str, JSON]) -> None:
-        # Backwards compat for 2.x API.
-        new_attrs = dict(self._obj.metadata.attributes)
-        new_attrs.update(d)
-        self._obj = self._obj.update_attributes(new_attrs)
+        """
+        Overwrite all attributes with the values from `d`.
+
+        Equivalent to the following pseudo-code, but performed atomically.
+
+        .. code-block:: python
+
+           >>> attrs = {"a": 1, "b": 2}
+           >>> attrs.clear()
+           >>> attrs.update({"a": 3", "c": 4})
+           >>> attrs
+           {'a': 3, 'c': 4}
+        """
+        self._obj = self._obj.update_attributes(d)

tests/v3/test_attributes.py

@@ -0,0 +1,13 @@
+import zarr.core
+import zarr.core.attributes
+import zarr.store
+
+
+def test_put():
+    store = zarr.store.MemoryStore({}, mode="w")
+    attrs = zarr.core.attributes.Attributes(
+        zarr.Group.from_store(store, attributes={"a": 1, "b": 2})
+    )
+    attrs.put({"a": 3, "c": 4})
+    expected = {"a": 3, "c": 4}
+    assert dict(attrs) == expected

tests/v3/test_group.py

@@ -155,7 +155,9 @@ def test_group_create(
     Test that `Group.from_store` works as expected.
     """
     attributes = {"foo": 100}
-    group = Group.from_store(store, attributes=attributes, zarr_format=zarr_format, exists_ok=exists_ok)
+    group = Group.from_store(
+        store, attributes=attributes, zarr_format=zarr_format, exists_ok=exists_ok
+    )
 
     assert group.attrs == attributes