REF: make BusinessMixin a cdef class

pandas/_libs/tslibs/offsets.pyx

@@ -988,13 +988,17 @@ def delta_to_tick(delta: timedelta) -> Tick:
 # --------------------------------------------------------------------
 
 
-class BusinessMixin(SingleConstructorOffset):
+cdef class BusinessMixin(SingleConstructorOffset):
     """
     Mixin to business types to provide related functions.
     """
+
+    cdef readonly:
+        timedelta _offset
+
     def __init__(self, n=1, normalize=False, offset=timedelta(0)):
         BaseOffset.__init__(self, n, normalize)
-        object.__setattr__(self, "_offset", offset)
+        self._offset = offset
 
     @property
     def offset(self):
@@ -1014,6 +1018,11 @@ class BusinessMixin(SingleConstructorOffset):
             out += ": " + ", ".join(attrs)
         return out
 
+    cpdef __setstate__(self, state):
+        # We need to use a cdef/cpdef method to set the readonly _offset attribute
+        BaseOffset.__setstate__(self, state)
+        self._offset = state["_offset"]
+
 
 class BusinessHourMixin(BusinessMixin):
     _adjust_dst = False
@@ -1067,6 +1076,9 @@ class BusinessHourMixin(BusinessMixin):
         object.__setattr__(self, "start", start)
         object.__setattr__(self, "end", end)
 
+    def __reduce__(self):
+        return type(self), (self.n, self.normalize, self.start, self.end, self.offset)
+
     def _repr_attrs(self) -> str:
         out = super()._repr_attrs()
         hours = ",".join(
@@ -1299,7 +1311,7 @@ cdef class QuarterOffset(SingleConstructorOffset):
         return type(dtindex)._simple_new(shifted, dtype=dtindex.dtype)
 
 
-cdef class MonthOffset(BaseOffset):
+cdef class MonthOffset(SingleConstructorOffset):
     def is_on_offset(self, dt) -> bool:
         if self.normalize and not is_normalized(dt):
             return False
@@ -1316,13 +1328,6 @@ cdef class MonthOffset(BaseOffset):
         shifted = shift_months(dtindex.asi8, self.n, self._day_opt)
         return type(dtindex)._simple_new(shifted, dtype=dtindex.dtype)
 
-    @classmethod
-    def _from_name(cls, suffix=None):
-        # default _from_name calls cls with no args
-        if suffix:
-            raise ValueError(f"Bad freq suffix {suffix}")
-        return cls()
-
 
 # ----------------------------------------------------------------------
 # RelativeDelta Arithmetic

pandas/tseries/offsets.py

@@ -790,7 +790,7 @@ def __init__(
 # Month-Based Offset Classes
 
 
-class MonthEnd(SingleConstructorMixin, liboffsets.MonthOffset):
+class MonthEnd(liboffsets.MonthOffset):
     """
     DateOffset of one month end.
     """
@@ -799,7 +799,7 @@ class MonthEnd(SingleConstructorMixin, liboffsets.MonthOffset):
     _day_opt = "end"
 
 
-class MonthBegin(SingleConstructorMixin, liboffsets.MonthOffset):
+class MonthBegin(liboffsets.MonthOffset):
     """
     DateOffset of one month at beginning.
     """
@@ -808,7 +808,7 @@ class MonthBegin(SingleConstructorMixin, liboffsets.MonthOffset):
     _day_opt = "start"
 
 
-class BusinessMonthEnd(SingleConstructorMixin, liboffsets.MonthOffset):
+class BusinessMonthEnd(liboffsets.MonthOffset):
     """
     DateOffset increments between business EOM dates.
     """
@@ -817,7 +817,7 @@ class BusinessMonthEnd(SingleConstructorMixin, liboffsets.MonthOffset):
     _day_opt = "business_end"
 
 
-class BusinessMonthBegin(SingleConstructorMixin, liboffsets.MonthOffset):
+class BusinessMonthBegin(liboffsets.MonthOffset):
     """
     DateOffset of one business month at beginning.
     """
@@ -827,9 +827,7 @@ class BusinessMonthBegin(SingleConstructorMixin, liboffsets.MonthOffset):
 
 
 @doc(bound="bound")
-class _CustomBusinessMonth(
-    CustomMixin, BusinessMixin, SingleConstructorMixin, liboffsets.MonthOffset
-):
+class _CustomBusinessMonth(CustomMixin, BusinessMixin, liboffsets.MonthOffset):
     """
     DateOffset subclass representing custom business month(s).
 
@@ -871,6 +869,13 @@ def __init__(
         BusinessMixin.__init__(self, n, normalize, offset)
         CustomMixin.__init__(self, weekmask, holidays, calendar)
 
+    def __reduce__(self):
+        # None for self.calendar bc np.busdaycalendar doesnt pickle nicely
+        return (
+            type(self),
+            (self.n, self.normalize, self.weekmask, self.holidays, None, self.offset),
+        )
+
     @cache_readonly
     def cbday_roll(self):
         """