Add support for __round__ in Series and DataFrame (#14099)

Fixes: #14083 

This PR fixes builtin function `round` call on `DataFrame` & `Series` to work by implementing `__round__` method.

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Bradley Dice (https://github.com/bdice)

URL: #14099

python/cudf/cudf/core/indexed_frame.py

@@ -358,6 +358,12 @@ def _from_columns_like_self(
             override_dtypes=override_dtypes,
         )
 
+    def __round__(self, digits=0):
+        # Shouldn't be added to BinaryOperand
+        # because pandas Index doesn't implement
+        # this method.
+        return self.round(decimals=digits)
+
     def _mimic_inplace(
         self, result: Self, inplace: bool = False
     ) -> Optional[Self]:

python/cudf/cudf/tests/test_dataframe.py

@@ -10326,3 +10326,26 @@ def test_dataframe_nlargest_nsmallest_str_error(attr):
         ([], {"n": 1, "columns": ["a", "b"]}),
         ([], {"n": 1, "columns": ["a", "b"]}),
     )
+
+
+@pytest.mark.parametrize("digits", [0, 1, 3, 4, 10])
+def test_dataframe_round_builtin(digits):
+    pdf = pd.DataFrame(
+        {
+            "a": [1.2234242333234, 323432.3243423, np.nan],
+            "b": ["a", "b", "c"],
+            "c": pd.Series([34224, 324324, 324342], dtype="datetime64[ns]"),
+            "d": pd.Series([224.242, None, 2424.234324], dtype="category"),
+            "e": [
+                decimal.Decimal("342.3243234234242"),
+                decimal.Decimal("89.32432497687622"),
+                None,
+            ],
+        }
+    )
+    gdf = cudf.from_pandas(pdf, nan_as_null=False)
+
+    expected = round(pdf, digits)
+    actual = round(gdf, digits)
+
+    assert_eq(expected, actual)

python/cudf/cudf/tests/test_series.py

@@ -1,5 +1,6 @@
 # Copyright (c) 2020-2023, NVIDIA CORPORATION.
 
+import decimal
 import hashlib
 import operator
 import re
@@ -2282,3 +2283,31 @@ def test_series_rename(initial_name, name):
     expected = psr.rename(name)
 
     assert_eq(actual, expected)
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        [1.2234242333234, 323432.3243423, np.nan],
+        pd.Series([34224, 324324, 324342], dtype="datetime64[ns]"),
+        pd.Series([224.242, None, 2424.234324], dtype="category"),
+        [
+            decimal.Decimal("342.3243234234242"),
+            decimal.Decimal("89.32432497687622"),
+            None,
+        ],
+    ],
+)
+@pytest.mark.parametrize("digits", [0, 1, 3, 4, 10])
+def test_series_round_builtin(data, digits):
+    ps = pd.Series(data)
+    gs = cudf.from_pandas(ps, nan_as_null=False)
+
+    # TODO: Remove `to_frame` workaround
+    # after following issue is fixed:
+    # https://github.com/pandas-dev/pandas/issues/55114
+    expected = round(ps.to_frame(), digits)[0]
+    expected.name = None
+    actual = round(gs, digits)
+
+    assert_eq(expected, actual)