From 9373fbfb94244e0dae3f0dab799ae900d5aa7fc0 Mon Sep 17 00:00:00 2001
From: ritchie <ritchie46@gmail.com>
Date: Mon, 25 Nov 2024 07:57:36 +0100
Subject: [PATCH] fix: Fix `gather_every` for `Scalar`

---
 crates/polars-core/src/frame/column/mod.rs |  5 ++++-
 py-polars/tests/unit/test_scalar.py        | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/crates/polars-core/src/frame/column/mod.rs b/crates/polars-core/src/frame/column/mod.rs
index 70ce9b8855c7..585350c7627c 100644
--- a/crates/polars-core/src/frame/column/mod.rs
+++ b/crates/polars-core/src/frame/column/mod.rs
@@ -1101,7 +1101,10 @@ impl Column {
         match self {
             Column::Series(s) => s.gather_every(n, offset).into(),
             Column::Partitioned(s) => s.as_materialized_series().gather_every(n, offset).into(),
-            Column::Scalar(s) => s.resize(s.len() - offset / n).into(),
+            Column::Scalar(s) => {
+                let total = s.len() - offset;
+                s.resize(1 + (total - 1) / n).into()
+            },
         }
     }
 
diff --git a/py-polars/tests/unit/test_scalar.py b/py-polars/tests/unit/test_scalar.py
index 6fa59a6c323d..4b1e9c135d5c 100644
--- a/py-polars/tests/unit/test_scalar.py
+++ b/py-polars/tests/unit/test_scalar.py
@@ -36,3 +36,14 @@ def test_null_literals(dtype: pl.DataType) -> None:
         .collect_schema()
         .dtypes()
     ) == [pl.Int64, dtype]
+
+
+def test_scalar_19957() -> None:
+    value = 1
+    values = [value] * 5
+    foo = pl.DataFrame({"foo": values})
+    foo_with_bar_from_literal = foo.with_columns(pl.lit(value).alias("bar"))
+    assert foo_with_bar_from_literal.gather_every(2).to_dict(as_series=False) == {
+        "foo": [1, 1, 1],
+        "bar": [1, 1, 1],
+    }