fix(python): Raise if pass a negative n into clear (#15432)

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

py-polars/polars/dataframe/frame.py

@@ -6912,17 +6912,18 @@ def clear(self, n: int = 0) -> Self:
         │ null ┆ null ┆ null │
         └──────┴──────┴──────┘
         """
+        if n < 0:
+            msg = f"`n` should be greater than or equal to 0, got {n}"
+            raise ValueError(msg)
         # faster path
         if n == 0:
             return self._from_pydf(self._df.clear())
-        if n > 0 or len(self) > 0:
-            return self.__class__(
-                {
-                    nm: pl.Series(name=nm, dtype=tp).extend_constant(None, n)
-                    for nm, tp in self.schema.items()
-                }
-            )
-        return self.clone()
+        return self.__class__(
+            {
+                nm: pl.Series(name=nm, dtype=tp).extend_constant(None, n)
+                for nm, tp in self.schema.items()
+            }
+        )
 
     def clone(self) -> Self:
         """

py-polars/polars/series/series.py

@@ -4759,6 +4759,10 @@ def clear(self, n: int = 0) -> Series:
             null
         ]
         """
+        if n < 0:
+            msg = f"`n` should be greater than or equal to 0, got {n}"
+            raise ValueError(msg)
+        # faster path
         if n == 0:
             return self._from_pyseries(self._s.clear())
         s = (

py-polars/tests/unit/operations/test_clear.py

@@ -73,3 +73,13 @@ def test_clear_series_object_starting_with_null() -> None:
     assert result.dtype == s.dtype
     assert result.name == s.name
     assert result.is_empty()
+
+
+def test_clear_raise_negative_n() -> None:
+    s = pl.Series([1, 2, 3])
+
+    msg = "`n` should be greater than or equal to 0, got -1"
+    with pytest.raises(ValueError, match=msg):
+        s.clear(-1)
+    with pytest.raises(ValueError, match=msg):
+        s.to_frame().clear(-1)