REF: implement general case DateOffset methods on BaseOffset (#34099)

Author: jbrockmendel

pandas/_libs/tslibs/offsets.pyx

@@ -408,7 +408,7 @@ class _BaseOffset:
     _day_opt = None
     _attributes = frozenset(['n', 'normalize'])
     _use_relativedelta = False
-    _adjust_dst = False
+    _adjust_dst = True
     _deprecations = frozenset(["isAnchored", "onOffset"])
     normalize = False  # default for prior pickles
 
@@ -566,6 +566,26 @@ class _BaseOffset:
 
     # ------------------------------------------------------------------
 
+    @apply_index_wraps
+    def apply_index(self, index):
+        """
+        Vectorized apply of DateOffset to DatetimeIndex,
+        raises NotImplementedError for offsets without a
+        vectorized implementation.
+
+        Parameters
+        ----------
+        index : DatetimeIndex
+
+        Returns
+        -------
+        DatetimeIndex
+        """
+        raise NotImplementedError(
+            f"DateOffset subclass {type(self).__name__} "
+            "does not have a vectorized implementation"
+        )
+
     def rollback(self, dt):
         """
         Roll provided date backward to next offset only if not on offset.
@@ -599,6 +619,17 @@ class _BaseOffset:
         # will raise NotImplementedError.
         return get_day_of_month(other, self._day_opt)
 
+    def is_on_offset(self, dt) -> bool:
+        if self.normalize and not is_normalized(dt):
+            return False
+
+        # Default (slow) method for determining if some date is a member of the
+        # date range generated by this offset. Subclasses may have this
+        # re-implemented in a nicer way.
+        a = dt
+        b = (dt + self) - self
+        return a == b
+
     # ------------------------------------------------------------------
 
     def _validate_n(self, n):
@@ -712,6 +743,7 @@ cdef class _Tick(ABCTick):
 
     # ensure that reversed-ops with numpy scalars return NotImplemented
     __array_priority__ = 1000
+    _adjust_dst = False
 
     def is_on_offset(self, dt) -> bool:
         return True

pandas/tseries/offsets.py

@@ -176,6 +176,7 @@ def __add__(date):
     _params = cache_readonly(BaseOffset._params.fget)
     freqstr = cache_readonly(BaseOffset.freqstr.fget)
     _attributes = frozenset(["n", "normalize"] + list(liboffsets.relativedelta_kwds))
+    _adjust_dst = False
 
     def __init__(self, n=1, normalize=False, **kwds):
         BaseOffset.__init__(self, n, normalize)
@@ -228,11 +229,6 @@ def apply_index(self, i):
         -------
         y : DatetimeIndex
         """
-        if type(self) is not DateOffset:
-            raise NotImplementedError(
-                f"DateOffset subclass {type(self).__name__} "
-                "does not have a vectorized implementation"
-            )
         kwds = self.kwds
         relativedelta_fast = {
             "years",
@@ -308,18 +304,17 @@ def is_on_offset(self, dt):
         if self.normalize and not is_normalized(dt):
             return False
         # TODO, see #1395
-        if type(self) is DateOffset:
-            return True
-
-        # Default (slow) method for determining if some date is a member of the
-        # date range generated by this offset. Subclasses may have this
-        # re-implemented in a nicer way.
-        a = dt
-        b = (dt + self) - self
-        return a == b
+        return True
 
 
 class SingleConstructorOffset(DateOffset):
+    # All DateOffset subclasses (other than Tick) subclass SingleConstructorOffset
+    __init__ = BaseOffset.__init__
+    _attributes = BaseOffset._attributes
+    apply_index = BaseOffset.apply_index
+    is_on_offset = BaseOffset.is_on_offset
+    _adjust_dst = True
+
     @classmethod
     def _from_name(cls, suffix=None):
         # default _from_name calls cls with no args
@@ -334,7 +329,6 @@ class BusinessDay(BusinessMixin, SingleConstructorOffset):
     """
 
     _prefix = "B"
-    _adjust_dst = True
     _attributes = frozenset(["n", "normalize", "offset"])
 
     def __init__(self, n=1, normalize=False, offset=timedelta(0)):
@@ -441,6 +435,8 @@ def is_on_offset(self, dt: datetime) -> bool:
 
 
 class BusinessHourMixin(BusinessMixin):
+    _adjust_dst = False
+
     def __init__(self, start="09:00", end="17:00", offset=timedelta(0)):
         # must be validated here to equality check
         if not is_list_like(start):
@@ -912,11 +908,6 @@ def __init__(
 
 
 class MonthOffset(SingleConstructorOffset):
-    _adjust_dst = True
-    _attributes = frozenset(["n", "normalize"])
-
-    __init__ = BaseOffset.__init__
-
     def is_on_offset(self, dt: datetime) -> bool:
         if self.normalize and not is_normalized(dt):
             return False
@@ -997,8 +988,8 @@ class _CustomBusinessMonth(CustomMixin, BusinessMixin, MonthOffset):
         ["n", "normalize", "weekmask", "holidays", "calendar", "offset"]
     )
 
-    is_on_offset = DateOffset.is_on_offset  # override MonthOffset method
-    apply_index = DateOffset.apply_index  # override MonthOffset method
+    is_on_offset = BaseOffset.is_on_offset  # override MonthOffset method
+    apply_index = BaseOffset.apply_index  # override MonthOffset method
 
     def __init__(
         self,
@@ -1082,8 +1073,7 @@ class CustomBusinessMonthBegin(_CustomBusinessMonth):
 # Semi-Month Based Offset Classes
 
 
-class SemiMonthOffset(DateOffset):
-    _adjust_dst = True
+class SemiMonthOffset(SingleConstructorOffset):
     _default_day_of_month = 15
     _min_day_of_month = 2
     _attributes = frozenset(["n", "normalize", "day_of_month"])
@@ -1304,7 +1294,7 @@ def _apply_index_days(self, i, roll):
 # Week-Based Offset Classes
 
 
-class Week(DateOffset):
+class Week(SingleConstructorOffset):
     """
     Weekly offset.
 
@@ -1314,7 +1304,6 @@ class Week(DateOffset):
         Always generate specific day of week. 0 for Monday.
     """
 
-    _adjust_dst = True
     _inc = timedelta(weeks=1)
     _prefix = "W"
     _attributes = frozenset(["n", "normalize", "weekday"])
@@ -1446,7 +1435,7 @@ def is_on_offset(self, dt):
         return dt.day == self._get_offset_day(dt)
 
 
-class WeekOfMonth(_WeekOfMonthMixin, DateOffset):
+class WeekOfMonth(_WeekOfMonthMixin, SingleConstructorOffset):
     """
     Describes monthly dates like "the Tuesday of the 2nd week of each month".
 
@@ -1469,7 +1458,6 @@ class WeekOfMonth(_WeekOfMonthMixin, DateOffset):
     """
 
     _prefix = "WOM"
-    _adjust_dst = True
     _attributes = frozenset(["n", "normalize", "week", "weekday"])
 
     def __init__(self, n=1, normalize=False, week=0, weekday=0):
@@ -1516,7 +1504,7 @@ def _from_name(cls, suffix=None):
         return cls(week=week, weekday=weekday)
 
 
-class LastWeekOfMonth(_WeekOfMonthMixin, DateOffset):
+class LastWeekOfMonth(_WeekOfMonthMixin, SingleConstructorOffset):
     """
     Describes monthly dates in last week of month like "the last Tuesday of
     each month".
@@ -1537,7 +1525,6 @@ class LastWeekOfMonth(_WeekOfMonthMixin, DateOffset):
     """
 
     _prefix = "LWOM"
-    _adjust_dst = True
     _attributes = frozenset(["n", "normalize", "weekday"])
 
     def __init__(self, n=1, normalize=False, weekday=0):
@@ -1587,14 +1574,13 @@ def _from_name(cls, suffix=None):
 # Quarter-Based Offset Classes
 
 
-class QuarterOffset(DateOffset):
+class QuarterOffset(SingleConstructorOffset):
     """
     Quarter representation - doesn't call super.
     """
 
     _default_startingMonth: Optional[int] = None
     _from_name_startingMonth: Optional[int] = None
-    _adjust_dst = True
     _attributes = frozenset(["n", "normalize", "startingMonth"])
     # TODO: Consider combining QuarterOffset and YearOffset __init__ at some
     #       point.  Also apply_index, is_on_offset, rule_code if
@@ -1706,12 +1692,11 @@ class QuarterBegin(QuarterOffset):
 # Year-Based Offset Classes
 
 
-class YearOffset(DateOffset):
+class YearOffset(SingleConstructorOffset):
     """
     DateOffset that just needs a month.
     """
 
-    _adjust_dst = True
     _attributes = frozenset(["n", "normalize", "month"])
 
     def _get_offset_day(self, other: datetime) -> int:
@@ -1807,7 +1792,7 @@ class YearBegin(YearOffset):
 # Special Offset Classes
 
 
-class FY5253(DateOffset):
+class FY5253(SingleConstructorOffset):
     """
     Describes 52-53 week fiscal year. This is also known as a 4-4-5 calendar.
 
@@ -1856,7 +1841,6 @@ class FY5253(DateOffset):
     """
 
     _prefix = "RE"
-    _adjust_dst = True
     _attributes = frozenset(["weekday", "startingMonth", "variation"])
 
     def __init__(
@@ -2014,7 +1998,7 @@ def _from_name(cls, *args):
         return cls(**cls._parse_suffix(*args))
 
 
-class FY5253Quarter(DateOffset):
+class FY5253Quarter(SingleConstructorOffset):
     """
     DateOffset increments between business quarter dates
     for 52-53 week fiscal year (also known as a 4-4-5 calendar).
@@ -2071,7 +2055,6 @@ class FY5253Quarter(DateOffset):
     """
 
     _prefix = "REQ"
-    _adjust_dst = True
     _attributes = frozenset(
         ["weekday", "startingMonth", "qtr_with_extra_week", "variation"]
     )
@@ -2232,18 +2215,13 @@ def _from_name(cls, *args):
         )
 
 
-class Easter(DateOffset):
+class Easter(SingleConstructorOffset):
     """
     DateOffset for the Easter holiday using logic defined in dateutil.
 
     Right now uses the revised method which is valid in years 1583-4099.
     """
 
-    _adjust_dst = True
-    _attributes = frozenset(["n", "normalize"])
-
-    __init__ = BaseOffset.__init__
-
     @apply_wraps
     def apply(self, other):
         current_easter = easter(other.year)