Moved caching in AbstractHolidayCalendar to the instance level

doc/source/whatsnew/v0.16.1.txt

@@ -154,3 +154,4 @@ Bug Fixes
 
 - Bug where dividing a dataframe containing values of type ``Decimal`` by another ``Decimal`` would raise. (:issue:`9787`)
 - Bug where using DataFrames asfreq would remove the name of the index. (:issue:`9885`)
+- Changed caching in ``AbstractHolidayCalendar`` to be at the instance level rather than at the class level as the latter can result in unexpected behaviour. (:issue:`9552`)

pandas/tseries/holiday.py

@@ -279,7 +279,7 @@ class AbstractHolidayCalendar(object):
     rules = []
     start_date = Timestamp(datetime(1970, 1, 1))
     end_date = Timestamp(datetime(2030, 12, 31))
-    _holiday_cache = None
+    _cache = None
 
     def __init__(self, name=None, rules=None):
         """
@@ -351,14 +351,6 @@ def holidays(self, start=None, end=None, return_name=False):
         else:
             return holidays.index
 
-    @property
-    def _cache(self):
-        return self.__class__._holiday_cache
-
-    @_cache.setter
-    def _cache(self, values):
-        self.__class__._holiday_cache = values
-
     @staticmethod
     def merge_class(base, other):
         """

pandas/tseries/tests/test_holiday.py

@@ -1,6 +1,7 @@
 
 from datetime import datetime
 import pandas.util.testing as tm
+from pandas import DatetimeIndex
 from pandas.tseries.holiday import (
     USFederalHolidayCalendar, USMemorialDay, USThanksgivingDay,
     nearest_workday, next_monday_or_tuesday, next_monday,
@@ -50,6 +51,29 @@ def test_calendar(self):
         self.assertEqual(list(holidays_2.to_pydatetime()),
                          self.holiday_list)
 
+    def test_calendar_caching(self):
+        # Test for issue #9552
+
+        class TestCalendar(AbstractHolidayCalendar):
+            def __init__(self, name=None, rules=None):
+                super(TestCalendar, self).__init__(
+                    name=name,
+                    rules=rules
+                )
+
+        jan1 = TestCalendar(rules=[Holiday('jan1', year=2015, month=1, day=1)])
+        jan2 = TestCalendar(rules=[Holiday('jan2', year=2015, month=1, day=2)])
+
+        tm.assert_index_equal(
+            jan1.holidays(),
+            DatetimeIndex(['01-Jan-2015'])
+        )
+        tm.assert_index_equal(
+            jan2.holidays(),
+            DatetimeIndex(['02-Jan-2015'])
+        )
+
+
 class TestHoliday(tm.TestCase):
 
     def setUp(self):