fix(rust, python): fix top_k on empty (#5865)

pola-rs · Dec 20, 2022 · 3860fb2 · 3860fb2
1 parent 0fd735b
commit 3860fb2
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diff --git a/polars/polars-ops/src/chunked_array/top_k.rs b/polars/polars-ops/src/chunked_array/top_k.rs
@@ -60,6 +60,9 @@ where
 }
 
 pub fn top_k(s: &Series, k: usize, reverse: bool) -> PolarsResult<Series> {
+    if s.is_empty() {
+        return Ok(s.clone());
+    }
     let dtype = s.dtype();
 
     let s = s.to_physical_repr();

diff --git a/py-polars/tests/unit/test_empty.py b/py-polars/tests/unit/test_empty.py
@@ -8,3 +8,9 @@ def test_empty_str_concat_lit() -> None:
         "b": pl.Utf8,
         "literal": pl.Utf8,
     }
+
+
+def test_top_k_empty() -> None:
+    df = pl.DataFrame({"test": []})
+
+    assert df.select([pl.col("test").top_k(2)]).frame_equal(df)