From 956d7ee0dc4b8f3f9a9a13d7310dfba0d17a6fdb Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Mon, 18 May 2020 20:43:21 -0700
Subject: [PATCH 1/2] REF: make BusinessMixin a cdef class

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 17ea389611b84..3d0f1e55cb8de 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -973,13 +973,17 @@ def delta_to_tick(delta: timedelta) -> Tick:
 # --------------------------------------------------------------------
 
 
-class BusinessMixin(BaseOffset):
+cdef class BusinessMixin(BaseOffset):
     """
     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):

From 5bd9e0a86da648937369ef7badfb3c426525d3a2 Mon Sep 17 00:00:00 2001
From: jbrockmendel <jbrockmendel@gmail.com>
Date: Wed, 20 May 2020 20:22:46 -0700
Subject: [PATCH 2/2] REF: Make BusinessMixin a cdef class

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++++++
 pandas/tseries/offsets.py       | 7 +++++++
 2 files changed, 15 insertions(+)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 1c57b00de2690..8b00b6edba66b 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1011,6 +1011,11 @@ cdef class BusinessMixin(BaseOffset):
             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
@@ -1064,6 +1069,9 @@ 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(
diff --git a/pandas/tseries/offsets.py b/pandas/tseries/offsets.py
index 8aced50b78ae2..cbc707d4440a0 100644
--- a/pandas/tseries/offsets.py
+++ b/pandas/tseries/offsets.py
@@ -919,6 +919,13 @@ 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):
         """