Support cudf-polars str.reverse

python/cudf_polars/cudf_polars/dsl/expressions/string.py

@@ -127,6 +127,7 @@ def _validate_input(self) -> None:
             StringFunction.Name.StripCharsStart,
             StringFunction.Name.StripCharsEnd,
             StringFunction.Name.Uppercase,
+            StringFunction.Name.Reverse,
             StringFunction.Name.Tail,
             StringFunction.Name.Titlecase,
         ):
@@ -450,6 +451,9 @@ def do_evaluate(
                 plc.strings.replace.replace_multiple(column.obj, target.obj, repl.obj),
                 dtype=self.dtype,
             )
+        elif self.name is StringFunction.Name.Reverse:
+            (column,) = columns
+            return Column(plc.strings.reverse.reverse(column.obj), dtype=self.dtype)
         elif self.name is StringFunction.Name.Titlecase:
             (column,) = columns
             return Column(plc.strings.capitalize.title(column.obj))

python/cudf_polars/tests/expressions/test_stringfunction.py

@@ -472,6 +472,11 @@ def test_string_join(ldf, ignore_nulls, delimiter):
     assert_gpu_result_equal(q)
 
 
+def test_string_reverse(ldf):
+    q = ldf.select(pl.col("a").str.reverse())
+    assert_gpu_result_equal(q)
+
+
 def test_string_to_titlecase():
     df = pl.LazyFrame(
         {

python/pylibcudf/pylibcudf/libcudf/strings/reverse.pxd

@@ -0,0 +1,10 @@
+# Copyright (c) 2025, NVIDIA CORPORATION.
+from libcpp.memory cimport unique_ptr
+from pylibcudf.exception_handler cimport libcudf_exception_handler
+from pylibcudf.libcudf.column.column cimport column
+from pylibcudf.libcudf.column.column_view cimport column_view
+
+cdef extern from "cudf/strings/reverse.hpp" namespace "cudf::strings" nogil:
+    cdef unique_ptr[column] reverse(
+        column_view source_strings
+    ) except +libcudf_exception_handler

python/pylibcudf/pylibcudf/strings/CMakeLists.txt

@@ -1,5 +1,5 @@
 # =============================================================================
-# Copyright (c) 2024, NVIDIA CORPORATION.
+# Copyright (c) 2024-2025, NVIDIA CORPORATION.
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 # in compliance with the License. You may obtain a copy of the License at
@@ -29,6 +29,7 @@ set(cython_sources
     repeat.pyx
     replace.pyx
     replace_re.pyx
+    reverse.pyx
     side_type.pyx
     slice.pyx
     strip.pyx

python/pylibcudf/pylibcudf/strings/__init__.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2024, NVIDIA CORPORATION.
+# Copyright (c) 2024-2025, NVIDIA CORPORATION.
 
 from . import (
     attributes,
@@ -18,6 +18,7 @@
     repeat,
     replace,
     replace_re,
+    reverse,
     side_type,
     slice,
     split,
@@ -46,6 +47,7 @@
     "repeat",
     "replace",
     "replace_re",
+    "reverse",
     "slice",
     "split",
     "strip",

python/pylibcudf/pylibcudf/strings/reverse.pyx

@@ -0,0 +1,32 @@
+# Copyright (c) 2024-2025, NVIDIA CORPORATION.
+
+from libcpp.memory cimport unique_ptr
+from libcpp.utility cimport move
+from pylibcudf.column cimport Column
+from pylibcudf.libcudf.column.column cimport column
+from pylibcudf.libcudf.strings cimport reverse as cpp_reverse
+
+__all__ = ["reverse"]
+
+cpdef Column reverse(Column input):
+    """Reverses the characters within each string.
+
+    Any null string entries return corresponding null output column entries.
+
+    For details, see :cpp:func:`reverse`.
+
+    Parameters
+    ----------
+    input : Column
+        Strings column for this operation
+
+    Returns
+    -------
+    pylibcudf.Column
+        New strings column
+    """
+    cdef unique_ptr[column] c_result
+    with nogil:
+        c_result = cpp_reverse.reverse(input.view())
+
+    return Column.from_libcudf(move(c_result))

python/pylibcudf/pylibcudf/tests/test_string_reverse.py

@@ -0,0 +1,29 @@
+# Copyright (c) 2025, NVIDIA CORPORATION.
+
+import pyarrow as pa
+from utils import assert_column_eq
+
+import pylibcudf as plc
+
+
+def test_reverse():
+    arr = pa.array(
+        [
+            "bunny",
+            "rabbit",
+            "hare",
+            "dog",
+            "",
+            "a",
+            "  leading",
+            "trailing  ",
+            " mid dle ",
+            "123!@#",
+            None,
+        ]
+    )
+    got = plc.strings.reverse.reverse(
+        plc.Column.from_arrow(arr),
+    )
+    expect = pa.compute.utf8_reverse(arr)
+    assert_column_eq(expect, got)