Support pl.Expr.drop_nans in cudf_polars

Author: mroeschke

python/cudf_polars/cudf_polars/dsl/expressions/unary.py

@@ -104,6 +104,7 @@ class UnaryFunction(Expr):
     _supported_misc_fns = frozenset(
         {
             "as_struct",
+            "drop_nans",
             "drop_nulls",
             "fill_null",
             "fill_null_with_strategy",
@@ -329,6 +330,16 @@ def do_evaluate(
                 [keys_col, counts_col],
             )
             return Column(plc_column, dtype=self.dtype)
+        elif self.name == "drop_nans":
+            (column,) = (child.evaluate(df, context=context) for child in self.children)
+            if not plc.traits.is_floating_point(column.obj.type()):
+                return column
+            return Column(
+                plc.stream_compaction.drop_nans(
+                    plc.Table([column.obj]), [0], 1, stream=df.stream
+                ).columns()[0],
+                dtype=self.dtype,
+            )
         elif self.name == "drop_nulls":
             (column,) = (child.evaluate(df, context=context) for child in self.children)
             if column.null_count == 0:

python/cudf_polars/tests/expressions/test_drop_nans.py

@@ -0,0 +1,26 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+import pytest
+
+import polars as pl
+
+from cudf_polars.testing.asserts import assert_gpu_result_equal
+
+
+@pytest.mark.parametrize(
+    "series",
+    [
+        pl.Series("a", [1.0, float("nan"), 3.0, None, float("nan")]),
+        pl.Series("a", [1.0, 2.0, 3.0]),
+        pl.Series("a", [float("nan"), float("nan")]),
+        pl.Series("a", [None, None], dtype=pl.Float64),
+        pl.Series("a", [1, 2, None, 3], dtype=pl.Int64),
+        pl.Series("a", [], dtype=pl.Float64),
+    ],
+)
+def test_drop_nans(engine: pl.GPUEngine, series: pl.Series) -> None:
+    lf = pl.LazyFrame({"a": series})
+    q = lf.select(pl.col("a").drop_nans())
+    assert_gpu_result_equal(q, engine=engine)