add some index/range checks

py-polars/polars/dataframe/frame.py

@@ -4575,8 +4575,14 @@ def insert_column(self, index: int, column: IntoExprColumn) -> DataFrame:
         │ 4   ┆ 13.0 ┆ true  ┆ 0.0  │
         └─────┴──────┴───────┴──────┘
         """
-        if index < 0:
+        if (original_index := index) < 0:
             index = len(self.columns) + index
+            if index < 0:
+                msg = f"column index {original_index} is out of range (frame has {len(self.columns)} columns)"
+                raise IndexError(msg)
+        elif index > len(self.columns):
+            msg = f"column index {original_index} is out of range (frame has {len(self.columns)} columns)"
+            raise IndexError(msg)
 
         if isinstance(column, pl.Series):
             self._df.insert_column(index, column._s)

py-polars/tests/unit/dataframe/test_df.py

@@ -489,6 +489,17 @@ def test_insert_column() -> None:
     )
     assert_frame_equal(df, expected)
 
+    # check that we raise suitable index errors
+    for idx, column in (
+        (10, pl.col("v1").sqrt().alias("v1_sqrt")),
+        (-10, pl.Series("foo", [1, 2, 3])),
+    ):
+        with pytest.raises(
+            IndexError,
+            match=rf"column index {idx} is out of range \(frame has 5 columns\)",
+        ):
+            df.insert_column(idx, column)
+
 
 def test_replace_column() -> None:
     df = (