fix: Series.is_in

Author: dangotbanned

narwhals/series.py

@@ -14,6 +14,7 @@
     is_compliant_series,
     is_eager_allowed,
     is_index_selector,
+    iterable_to_sequence,
     qualified_type_name,
     supports_arrow_c_stream,
 )
@@ -25,7 +26,6 @@
 from narwhals.series_list import SeriesListNamespace
 from narwhals.series_str import SeriesStringNamespace
 from narwhals.series_struct import SeriesStructNamespace
-from narwhals.translate import to_native
 from narwhals.typing import IntoSeriesT
 
 if TYPE_CHECKING:
@@ -948,9 +948,12 @@ def is_in(self, other: Any) -> Self:
               ]
             ]
         """
-        return self._with_compliant(
-            self._compliant_series.is_in(to_native(other, pass_through=True))
+        other = (
+            other.to_native()
+            if isinstance(other, Series)
+            else iterable_to_sequence(other, backend=self.implementation)
         )
+        return self._with_compliant(self._compliant_series.is_in(other))
 
     def arg_true(self) -> Self:
         """Find elements where boolean Series is True.

tests/expr_and_series/is_in_test.py

@@ -67,10 +67,21 @@ def test_filter_is_in_with_series(constructor_eager: ConstructorEager) -> None:
 
 
 def test_ser_is_in_iterable(
-    constructor_eager: ConstructorEager, into_iter_16: IntoIterable
+    constructor_eager: ConstructorEager,
+    into_iter_16: IntoIterable,
+    request: pytest.FixtureRequest,
 ) -> None:
-    ser = nw.from_native(constructor_eager(data)).get_column("a")
+    test_name = request.node.name
+    # NOTE: This *could* be supported by using `ExtensionArray.tolist` (same path as numpy)
+    request.applymarker(
+        pytest.mark.xfail(
+            ("polars" in test_name and "pandas" in test_name and "array" in test_name),
+            raises=TypeError,
+            reason="Polars doesn't support `pd.array`.\nhttps://github.com/pola-rs/polars/issues/22757",
+        )
+    )
     iterable = into_iter_16((4, 2))
+    ser = nw.from_native(constructor_eager(data)).get_column("a")
     result = ser.is_in(iterable)
     expected = [False, True, True, False]
     assert_equal_series(result, expected, "a")