fix(python): Raise if invalid strategy is passed to map_elements (#…

…14397)

Co-authored-by: Stijn de Gooijer <[email protected]>

py-polars/polars/expr/expr.py

@@ -4411,7 +4411,8 @@ def get_lazy_promise(df: DataFrame) -> LazyFrame:
                 wrap_threading, agg_list=True, return_dtype=return_dtype
             )
         else:
-            ValueError(f"Strategy {strategy} is not supported.")
+            msg = f"strategy {strategy!r} is not supported"
+            raise ValueError(msg)
 
     def flatten(self) -> Self:
         """

py-polars/tests/unit/operations/map/test_map_elements.py

@@ -300,3 +300,11 @@ def test_apply_deprecated() -> None:
         pl.col("a").apply(np.abs)
     with pytest.deprecated_call():
         pl.Series([1, 2, 3]).apply(np.abs)
+
+
+def test_cabbage_strategy_14396() -> None:
+    df = pl.DataFrame({"x": [1, 2, 3]})
+    with pytest.raises(
+        ValueError, match="strategy 'cabbage' is not supported"
+    ), pytest.warns(PolarsInefficientMapWarning):
+        df.select(pl.col("x").map_elements(lambda x: 2 * x, strategy="cabbage"))  # type: ignore[arg-type]