API: all offset operations now return Timestamp types (rather than datetime) (GH4069)

doc/source/release.rst

@@ -150,6 +150,8 @@ API Changes
 
 - ``DataFrame.sort`` now places NaNs at the beginning or end of the sort according to the ``na_position`` parameter. (:issue:`3917`)
 
+- all offset operations now return ``Timestamp`` types (rather than datetime), Business/Week frequencies were incorrect (:issue:`4069`)
+
 Deprecations
 ~~~~~~~~~~~~
 

pandas/tseries/offsets.py

@@ -472,9 +472,9 @@ def _set_busdaycalendar(self):
             kwargs = {'weekmask':self.weekmask,'holidays':self.holidays}
         else:
             kwargs = {'weekmask':self.weekmask}
-        try: 
+        try:
             self.busdaycalendar = np.busdaycalendar(**kwargs)
-        except: 
+        except:
             # Check we have the required numpy version
             from distutils.version import LooseVersion
 
@@ -484,9 +484,9 @@ def _set_busdaycalendar(self):
                                           np.__version__)
             else:
                 raise
-            
+
     def __getstate__(self):
-        """"Return a pickleable state"""
+        """Return a pickleable state"""
         state = self.__dict__.copy()
         del state['busdaycalendar']
         return state
@@ -520,7 +520,7 @@ def apply(self, other):
             if self.offset:
                 result = result + self.offset
 
-            return result
+            return as_timestamp(result)
 
         elif isinstance(other, np.datetime64):
             dtype = other.dtype
@@ -539,7 +539,7 @@ def apply(self, other):
             if self.offset:
                 result = result + self.offset
 
-            return result
+            return as_timestamp(result)
 
         elif isinstance(other, (timedelta, Tick)):
             return BDay(self.n, offset=self.offset + other,
@@ -639,7 +639,7 @@ def apply(self, other):
 
         if other.weekday() > 4:
             other = other - BDay()
-        return other
+        return as_timestamp(other)
 
     _prefix = 'BM'
 
@@ -706,7 +706,7 @@ def isAnchored(self):
 
     def apply(self, other):
         if self.weekday is None:
-            return as_datetime(other) + self.n * self._inc
+            return as_timestamp(as_datetime(other) + self.n * self._inc)
 
         if self.n > 0:
             k = self.n
@@ -998,7 +998,7 @@ def apply(self, other):
         if other.weekday() > 4:
             other = other - BDay()
 
-        return other
+        return as_timestamp(other)
 
     def onOffset(self, dt):
         modMonth = (dt.month - self.startingMonth) % 3
@@ -1188,7 +1188,7 @@ def apply(self, other):
         if result.weekday() > 4:
             result = result - BDay()
 
-        return result
+        return as_timestamp(result)
 
 
 class BYearBegin(YearOffset):

pandas/tseries/tests/test_offsets.py

@@ -99,7 +99,7 @@ class TestBase(tm.TestCase):
 
     def test_apply_out_of_range(self):
         if self._offset is None:
-            raise nose.SkipTest("_offset not defined")
+            raise nose.SkipTest("_offset not defined to test out-of-range")
 
         # try to create an out-of-bounds result timestamp; if we can't create the offset
         # skip
@@ -113,6 +113,17 @@ def test_apply_out_of_range(self):
         except (ValueError, KeyError):
             raise nose.SkipTest("cannot create out_of_range offset")
 
+    def test_return_type(self):
+
+        # make sure that we are returning a Timestamp
+        try:
+            offset = self._offset(1)
+        except:
+            raise nose.SkipTest("_offset not defined to test return_type")
+
+        result = Timestamp('20080101') + offset
+        self.assertIsInstance(result, Timestamp)
+
 class TestDateOffset(TestBase):
     _multiprocess_can_split_ = True