REF: Make WeekOfMonthMixin a cdef class (#34265)

Author: jbrockmendel

doc/source/reference/offset_frequency.rst

@@ -549,6 +549,7 @@ Methods
     WeekOfMonth.is_anchored
     WeekOfMonth.is_on_offset
     WeekOfMonth.__call__
+    WeekOfMonth.weekday
 
 LastWeekOfMonth
 ---------------
@@ -569,6 +570,7 @@ Properties
     LastWeekOfMonth.normalize
     LastWeekOfMonth.rule_code
     LastWeekOfMonth.n
+    LastWeekOfMonth.weekday
 
 Methods
 ~~~~~~~

pandas/_libs/tslibs/offsets.pyx

@@ -562,6 +562,7 @@ cdef class BaseOffset:
         exclude = {"n", "inc", "normalize"}
         attrs = []
         for attr in sorted(self._attributes):
+            # _attributes instead of __dict__ because cython attrs are not in __dict__
             if attr.startswith("_") or attr == "kwds" or not hasattr(self, attr):
                 # DateOffset may not have some of these attributes
                 continue
@@ -1164,13 +1165,17 @@ class CustomMixin:
         object.__setattr__(self, "calendar", calendar)
 
 
-class WeekOfMonthMixin(SingleConstructorOffset):
+cdef class WeekOfMonthMixin(SingleConstructorOffset):
     """
     Mixin for methods common to WeekOfMonth and LastWeekOfMonth.
     """
+
+    cdef readonly:
+        int weekday
+
     def __init__(self, n=1, normalize=False, weekday=0):
         BaseOffset.__init__(self, n, normalize)
-        object.__setattr__(self, "weekday", weekday)
+        self.weekday = weekday
 
         if weekday < 0 or weekday > 6:
             raise ValueError(f"Day must be 0<=day<=6, got {weekday}")

pandas/tests/tseries/offsets/test_offsets.py

@@ -655,6 +655,19 @@ def test_pickle_v0_15_2(self, datapath):
         #
         tm.assert_dict_equal(offsets, read_pickle(pickle_path))
 
+    def test_pickle_roundtrip(self, offset_types):
+        off = self._get_offset(offset_types)
+        res = tm.round_trip_pickle(off)
+        assert off == res
+        if type(off) is not DateOffset:
+            for attr in off._attributes:
+                if attr == "calendar":
+                    # np.busdaycalendar __eq__ will return False;
+                    #  we check holidays and weekmask attrs so are OK
+                    continue
+                # Make sure nothings got lost from _params (which __eq__) is based on
+                assert getattr(off, attr) == getattr(res, attr)
+
     def test_onOffset_deprecated(self, offset_types):
         # GH#30340 use idiomatic naming
         off = self._get_offset(offset_types)
@@ -3463,6 +3476,11 @@ def test_is_on_offset(self, case):
         offset = LastWeekOfMonth(weekday=weekday)
         assert offset.is_on_offset(dt) == expected
 
+    def test_repr(self):
+        assert (
+            repr(LastWeekOfMonth(n=2, weekday=1)) == "<2 * LastWeekOfMonths: weekday=1>"
+        )
+
 
 class TestSemiMonthEnd(Base):
     _offset = SemiMonthEnd

pandas/tseries/offsets.py

@@ -310,8 +310,53 @@ def is_on_offset(self, dt):
         # TODO, see #1395
         return True
 
+    def _repr_attrs(self) -> str:
+        # The DateOffset class differs from other classes in that members
+        #  of self._attributes may not be defined, so we have to use __dict__
+        #  instead.
+        exclude = {"n", "inc", "normalize"}
+        attrs = []
+        for attr in sorted(self.__dict__):
+            if attr.startswith("_") or attr == "kwds":
+                continue
+            elif attr not in exclude:
+                value = getattr(self, attr)
+                attrs.append(f"{attr}={value}")
+
+        out = ""
+        if attrs:
+            out += ": " + ", ".join(attrs)
+        return out
 
-class BusinessDay(BusinessMixin, SingleConstructorOffset):
+    @cache_readonly
+    def _params(self):
+        """
+        Returns a tuple containing all of the attributes needed to evaluate
+        equality between two DateOffset objects.
+        """
+        # The DateOffset class differs from other classes in that members
+        #  of self._attributes may not be defined, so we have to use __dict__
+        #  instead.
+        all_paras = self.__dict__.copy()
+        all_paras["n"] = self.n
+        all_paras["normalize"] = self.normalize
+        for key in self.__dict__:
+            if key not in all_paras:
+                # cython attributes are not in __dict__
+                all_paras[key] = getattr(self, key)
+
+        if "holidays" in all_paras and not all_paras["holidays"]:
+            all_paras.pop("holidays")
+        exclude = ["kwds", "name", "calendar"]
+        attrs = [
+            (k, v) for k, v in all_paras.items() if (k not in exclude) and (k[0] != "_")
+        ]
+        attrs = sorted(set(attrs))
+        params = tuple([str(type(self))] + attrs)
+        return params
+
+
+class BusinessDay(BusinessMixin):
     """
     DateOffset subclass representing possibly n business days.
     """
@@ -796,6 +841,22 @@ def __init__(
         BusinessHour.__init__(self, n, normalize, start=start, end=end, offset=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.start,
+                self.end,
+                self.offset,
+            ),
+        )
+
 
 # ---------------------------------------------------------------------
 # Month-Based Offset Classes
@@ -1286,6 +1347,9 @@ def __init__(self, n=1, normalize=False, week=0, weekday=0):
         if self.week < 0 or self.week > 3:
             raise ValueError(f"Week must be 0<=week<=3, got {self.week}")
 
+    def __reduce__(self):
+        return type(self), (self.n, self.normalize, self.week, self.weekday)
+
     def _get_offset_day(self, other: datetime) -> int:
         """
         Find the day in the same month as other that has the same
@@ -1345,6 +1409,9 @@ def __init__(self, n=1, normalize=False, weekday=0):
             raise ValueError("N cannot be 0")
         object.__setattr__(self, "week", -1)
 
+    def __reduce__(self):
+        return type(self), (self.n, self.normalize, self.weekday)
+
     def _get_offset_day(self, other: datetime) -> int:
         """
         Find the day in the same month as other that has the same