From 7fa8a3ebe2ebc1009d877000cb40d7afd8821997 Mon Sep 17 00:00:00 2001
From: Weijie Guo <reswqa@163.com>
Date: Wed, 3 Apr 2024 17:24:47 +0800
Subject: [PATCH] fix(python): Raise if pass a negative `n` into `clear`
 (#15432)

Co-authored-by: Stijn de Gooijer <stijndegooijer@gmail.com>
---
 py-polars/polars/dataframe/frame.py           | 17 +++++++++--------
 py-polars/polars/series/series.py             |  4 ++++
 py-polars/tests/unit/operations/test_clear.py | 10 ++++++++++
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/py-polars/polars/dataframe/frame.py b/py-polars/polars/dataframe/frame.py
index a34c4aae5b84..8b9caf5a3a85 100644
--- a/py-polars/polars/dataframe/frame.py
+++ b/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:
         """
diff --git a/py-polars/polars/series/series.py b/py-polars/polars/series/series.py
index a651f8f77508..74834ecde8c8 100644
--- a/py-polars/polars/series/series.py
+++ b/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 = (
diff --git a/py-polars/tests/unit/operations/test_clear.py b/py-polars/tests/unit/operations/test_clear.py
index 0ac3c1d27ba0..c9a2d29c1492 100644
--- a/py-polars/tests/unit/operations/test_clear.py
+++ b/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)