add support for PyArrow: multi-element __getitem__ (#949)

narwhals/_arrow/series.py

@@ -321,6 +321,8 @@ def __getitem__(self, idx: slice | Sequence[int]) -> Self: ...
     def __getitem__(self, idx: int | slice | Sequence[int]) -> Any | Self:
         if isinstance(idx, int):
             return self._native_series[idx]
+        if isinstance(idx, Sequence):
+            return self._from_native_series(self._native_series.take(idx))
         return self._from_native_series(self._native_series[idx])
 
     def scatter(self, indices: int | Sequence[int], values: Any) -> Self:

tests/series_only/slice_test.py

@@ -0,0 +1,15 @@
+from typing import Any
+
+import narwhals.stable.v1 as nw
+from tests.utils import compare_dicts
+
+
+def test_slice(constructor_eager: Any) -> None:
+    data = {"a": [1, 2, 3], "b": [4, 5, 6], "c": [7, 8, 9], "d": [1, 4, 2]}
+    df = nw.from_native(constructor_eager(data), eager_only=True)
+    result = {"a": df["a"][[0, 1]]}
+    expected = {"a": [1, 2]}
+    compare_dicts(result, expected)
+    result = {"a": df["a"][1:]}
+    expected = {"a": [2, 3]}
+    compare_dicts(result, expected)