fix: Fix mode panicking for String dtype (#20458)

Co-authored-by: Ritchie Vink <[email protected]>
pola-rs · Dec 26, 2024 · 53cda2a · 53cda2a
1 parent 0d4f8e7
commit 53cda2a
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diff --git a/crates/polars-ops/src/chunked_array/mode.rs b/crates/polars-ops/src/chunked_array/mode.rs
@@ -61,7 +61,10 @@ pub fn mode(s: &Series) -> PolarsResult<Series> {
         DataType::Boolean => mode_primitive(s_phys.bool().unwrap())?.into_series(),
         DataType::Float32 => mode_f32(s_phys.f32().unwrap())?.into_series(),
         DataType::Float64 => mode_64(s_phys.f64().unwrap())?.into_series(),
-        DataType::String => mode_primitive(&s_phys.str().unwrap().as_binary())?.into_series(),
+        DataType::String => {
+            let ca = mode_primitive(&s_phys.str().unwrap().as_binary())?;
+            unsafe { ca.to_string_unchecked() }.into_series()
+        },
         dt if dt.is_integer() => {
             with_match_physical_integer_polars_type!(dt, |$T| {
                 let ca: &ChunkedArray<$T> = s_phys.as_ref().as_ref().as_ref();

diff --git a/py-polars/tests/unit/series/test_series.py b/py-polars/tests/unit/series/test_series.py
@@ -994,6 +994,7 @@ def test_mode() -> None:
         == "bar"
     )
     assert pl.Series([1.0, 2.0, 3.0, 2.0]).mode().item() == 2.0
+    assert pl.Series(["a", "b", "c", "b"]).mode().item() == "b"
 
     # sorted data
     assert set(pl.int_range(0, 3, eager=True).mode().to_list()) == {0, 1, 2}