feat: add isocalendar() for dt accessor

bigframes/core/compile/scalar_op_compiler.py

@@ -667,6 +667,22 @@ def date_op_impl(x: ibis_types.Value):
     return typing.cast(ibis_types.TimestampValue, x).date()
 
 
+@scalar_op_compiler.register_unary_op(ops.iso_day_op)
+def iso_day_op_impl(x: ibis_types.Value):
+    # Plus 1 because iso day of week uses 1-based indexing
+    return dayofweek_op_impl(x) + 1
+
+
+@scalar_op_compiler.register_unary_op(ops.iso_week_op)
+def iso_week_op_impl(x: ibis_types.Value):
+    return typing.cast(ibis_types.TimestampValue, x).week_of_year()
+
+
+@scalar_op_compiler.register_unary_op(ops.iso_year_op)
+def iso_year_op_impl(x: ibis_types.Value):
+    return typing.cast(ibis_types.TimestampValue, x).iso_year()
+
+
 @scalar_op_compiler.register_unary_op(ops.dayofweek_op)
 def dayofweek_op_impl(x: ibis_types.Value):
     return (

bigframes/operations/__init__.py

@@ -43,6 +43,9 @@
     day_op,
     dayofweek_op,
     dayofyear_op,
+    iso_day_op,
+    iso_week_op,
+    iso_year_op,
     month_op,
     quarter_op,
     year_op,
@@ -260,11 +263,14 @@
     # Date ops
     "date_diff_op",
     "day_op",
-    "month_op",
-    "year_op",
     "dayofweek_op",
     "dayofyear_op",
+    "iso_day_op",
+    "iso_week_op",
+    "iso_year_op",
+    "month_op",
     "quarter_op",
+    "year_op",
     # Time ops
     "hour_op",
     "minute_op",

bigframes/operations/date_ops.py

@@ -34,6 +34,20 @@
     type_signature=op_typing.DATELIKE_ACCESSOR,
 )
 
+iso_day_op = base_ops.create_unary_op(
+    name="iso_day", type_signature=op_typing.DATELIKE_ACCESSOR
+)
+
+iso_week_op = base_ops.create_unary_op(
+    name="iso_weeek",
+    type_signature=op_typing.DATELIKE_ACCESSOR,
+)
+
+iso_year_op = base_ops.create_unary_op(
+    name="iso_year",
+    type_signature=op_typing.DATELIKE_ACCESSOR,
+)
+
 dayofweek_op = base_ops.create_unary_op(
     name="dayofweek",
     type_signature=op_typing.DATELIKE_ACCESSOR,

bigframes/operations/datetimes.py

@@ -21,11 +21,11 @@
 import bigframes_vendored.pandas.core.indexes.accessor as vendordt
 import pandas
 
-from bigframes import dtypes
+from bigframes import dataframe, dtypes, series
 from bigframes.core import log_adapter
+from bigframes.core.reshape import concat
 import bigframes.operations as ops
 import bigframes.operations.base
-import bigframes.series as series
 
 _ONE_DAY = pandas.Timedelta("1d")
 _ONE_SECOND = pandas.Timedelta("1s")
@@ -69,6 +69,15 @@ def year(self) -> series.Series:
     def month(self) -> series.Series:
         return self._apply_unary_op(ops.month_op)
 
+    def isocalendar(self) -> dataframe.DataFrame:
+        years = self._apply_unary_op(ops.iso_year_op)
+        weeks = self._apply_unary_op(ops.iso_week_op)
+        days = self._apply_unary_op(ops.iso_day_op)
+
+        result = concat.concat([years, weeks, days], axis=1)
+        result.columns = pandas.Index(["year", "week", "day"])
+        return result
+
     # Time accessors
     @property
     def hour(self) -> series.Series:

tests/system/small/operations/test_datetimes.py

@@ -229,6 +229,21 @@ def test_dt_year(scalars_dfs, col_name):
     )
 
 
+def test_dt_isocalendar(session):
+    # We don't re-use the exisintg scalars_dfs fixture because iso calendar
+    # get tricky when a new year starts, but the dataset `scalars_dfs` does not cover
+    # this case.
+    pd_s = pd.Series(pd.date_range("2009-12-25", "2010-01-07", freq="d"))
+    bf_s = session.read_pandas(pd_s)
+
+    actual_result = bf_s.dt.isocalendar().to_pandas()
+
+    expected_result = pd_s.dt.isocalendar()
+    testing.assert_frame_equal(
+        actual_result, expected_result, check_dtype=False, check_index_type=False
+    )
+
+
 @pytest.mark.parametrize(
     ("col_name",),
     DATETIME_COL_NAMES,

third_party/bigframes_vendored/pandas/core/indexes/accessor.py

@@ -199,6 +199,38 @@ def month(self):
 
         raise NotImplementedError(constants.ABSTRACT_METHOD_ERROR_MESSAGE)
 
+    def isocalendar(self):
+        """
+        Calculate year, week, and day according to the ISO 8601 standard.
+
+        **Examples:**
+            >>> import pandas as pd
+            >>> import bigframes.pandas as bpd
+            >>> bpd.options.display.progress_bar = None
+            >>> s = bpd.Series(
+            ...     pd.date_range('2009-12-27', '2010-01-04', freq='d').to_series()
+            ... )
+            >>> s.dt.isocalendar()
+                                 year  week  day
+            2009-12-27 00:00:00  2009    52    7
+            2009-12-28 00:00:00  2009    53    1
+            2009-12-29 00:00:00  2009    53    2
+            2009-12-30 00:00:00  2009    53    3
+            2009-12-31 00:00:00  2009    53    4
+            2010-01-01 00:00:00  2009    53    5
+            2010-01-02 00:00:00  2009    53    6
+            2010-01-03 00:00:00  2009    53    7
+            2010-01-04 00:00:00  2010     1    1
+            <BLANKLINE>
+            [9 rows x 3 columns]
+
+
+        Returns: DataFrame
+            With columns year, week and day.
+
+
+        """
+
     @property
     def second(self):
         """The seconds of the datetime.