Backport PR #45087: BUG: Timestamp.to_pydatetime losing 'fold' (#45330)

Co-authored-by: jbrockmendel <[email protected]>

Author: meeseeksmachine

doc/source/whatsnew/v1.4.0.rst

@@ -724,6 +724,7 @@ Datetimelike
 - ``np.maximum.reduce`` and ``np.minimum.reduce`` now correctly return :class:`Timestamp` and :class:`Timedelta` objects when operating on :class:`Series`, :class:`DataFrame`, or :class:`Index` with ``datetime64[ns]`` or ``timedelta64[ns]`` dtype (:issue:`43923`)
 - Bug in adding a ``np.timedelta64`` object to a :class:`BusinessDay` or :class:`CustomBusinessDay` object incorrectly raising (:issue:`44532`)
 - Bug in :meth:`Index.insert` for inserting ``np.datetime64``, ``np.timedelta64`` or ``tuple`` into :class:`Index` with ``dtype='object'`` with negative loc adding ``None`` and replacing existing value (:issue:`44509`)
+- Bug in :meth:`Timestamp.to_pydatetime` failing to retain the ``fold`` attribute (:issue:`45087`)
 - Bug in :meth:`Series.mode` with ``DatetimeTZDtype`` incorrectly returning timezone-naive and ``PeriodDtype`` incorrectly raising (:issue:`41927`)
 - Bug in :class:`DateOffset`` addition with :class:`Timestamp` where ``offset.nanoseconds`` would not be included in the result (:issue:`43968`, :issue:`36589`)
 - Bug in :meth:`Timestamp.fromtimestamp` not supporting the ``tz`` argument (:issue:`45083`)

pandas/_libs/tslibs/timestamps.pyx

@@ -898,7 +898,7 @@ cdef class _Timestamp(ABCTimestamp):
 
         return datetime(self.year, self.month, self.day,
                         self.hour, self.minute, self.second,
-                        self.microsecond, self.tzinfo)
+                        self.microsecond, self.tzinfo, fold=self.fold)
 
     cpdef to_datetime64(self):
         """

pandas/tests/scalar/timestamp/test_timestamp.py

@@ -592,6 +592,13 @@ def test_conversion(self):
         assert type(result) == type(expected)
         assert result.dtype == expected.dtype
 
+    def test_to_pydatetime_fold(self):
+        # GH#45087
+        tzstr = "dateutil/usr/share/zoneinfo/America/Chicago"
+        ts = Timestamp(year=2013, month=11, day=3, hour=1, minute=0, fold=1, tz=tzstr)
+        dt = ts.to_pydatetime()
+        assert dt.fold == 1
+
     def test_to_pydatetime_nonzero_nano(self):
         ts = Timestamp("2011-01-01 9:00:00.123456789")
 

pandas/tests/scalar/timestamp/test_timezones.py

@@ -166,9 +166,9 @@ def test_tz_localize_ambiguous_compat(self):
         assert result_pytz.value == 1382835600000000000
 
         # fixed ambiguous behavior
-        # see gh-14621
+        # see gh-14621, GH#45087
         assert result_pytz.to_pydatetime().tzname() == "GMT"
-        assert result_dateutil.to_pydatetime().tzname() == "BST"
+        assert result_dateutil.to_pydatetime().tzname() == "GMT"
         assert str(result_pytz) == str(result_dateutil)
 
         # 1 hour difference