BUG: Bug in resample with a timezone and certain offsets (GH6397)

Author: jreback

doc/source/release.rst

@@ -176,6 +176,7 @@ Bug Fixes
 - Bug in ``str.split`` when passed ``pat=None`` and ``n=1`` (:issue:`6466`)
 - Bug in ``io.data.DataReader`` when passed ``"F-F_Momentum_Factor"`` and ``data_source="famafrench"`` (:issue:`6460`)
 - Bug in ``sum`` of a ``timedelta64[ns]`` series (:issue:`6462`)
+- Bug in ``resample`` with a timezone and certain offsets (:issue:`6397`)
 
 pandas 0.13.1
 -------------

pandas/tseries/index.py

@@ -1067,7 +1067,13 @@ def _can_fast_union(self, other):
         left_end = left[-1]
 
         # Only need to "adjoin", not overlap
-        return (right_start == left_end + offset) or right_start in left
+        try:
+            return (right_start == left_end + offset) or right_start in left
+        except (ValueError):
+
+            # if we are comparing an offset that does not propogate timezones
+            # this will raise
+            return False
 
     def _fast_union(self, other):
         if len(other) == 0:

pandas/tseries/tests/test_resample.py

@@ -973,6 +973,18 @@ def test_resample_tz_localized(self):
         expected = Series([1.5], index=ex_index)
         assert_series_equal(result, expected)
 
+        # GH 6397
+        # comparing an offset that doesn't propogate tz's
+        rng = date_range('1/1/2011', periods=20000, freq='H')
+        rng = rng.tz_localize('EST')
+        ts = DataFrame(index=rng)
+        ts['first']=np.random.randn(len(rng))
+        ts['second']=np.cumsum(np.random.randn(len(rng)))
+        expected = DataFrame({ 'first' : ts.resample('A',how=np.sum)['first'],
+                               'second' : ts.resample('A',how=np.mean)['second'] },columns=['first','second'])
+        result = ts.resample('A', how={'first':np.sum, 'second':np.mean}).reindex(columns=['first','second'])
+        assert_frame_equal(result,expected)
+
     def test_closed_left_corner(self):
         # #1465
         s = Series(np.random.randn(21),