core: cast result to TimeDeltaBlock if needed

Author: holymonson

pandas/core/internals/__init__.py

@@ -63,7 +63,9 @@
     ABCSeries,
     ABCDatetimeIndex,
     ABCExtensionArray,
-    ABCIndexClass)
+    ABCIndexClass,
+    ABCDateOffset,
+)
 import pandas.core.common as com
 import pandas.core.algorithms as algos
 
@@ -2785,11 +2787,16 @@ def set(self, locs, values, check=False):
 
         self.values[locs] = values
 
-    def eval(self, try_cast=False, *args, **kwargs):
-        blocks = super().eval(try_cast=try_cast, *args, **kwargs)
+    def eval(self, func, other, try_cast=False, **kwargs):
+        block = super().eval(func, other, try_cast=try_cast, **kwargs)[0]
         if try_cast:
-            blocks = [self._try_coerce_result(block) for block in blocks]
-        return blocks
+            if isinstance(other,
+                          (tslibs.Timestamp, np.datetime64, datetime, date)):
+                block = TimeDeltaBlock(block.values, block.mgr_locs,
+                                       ndim=block.ndim)
+            elif isinstance(other, ABCDateOffset):
+                block = self._try_coerce_result(block)
+        return [block]
 
 
 class DatetimeTZBlock(NonConsolidatableMixIn, DatetimeBlock):

pandas/tests/frame/test_arithmetic.py

@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import datetime
 import pytest
 import numpy as np
 
@@ -221,6 +222,17 @@ def test_timestamp_df_add_dateoffset(self):
                   + pd.DateOffset(years=1))
         tm.assert_frame_equal(expected, result)
 
+    @pytest.mark.parametrize('other', [
+        pd.Timestamp('2017'),
+        np.datetime64('2017'),
+        datetime.datetime(2017, 1, 1),
+        datetime.date(2017, 1, 1),
+    ])
+    def test_timestamp_df_sub_timestamp(self, other):
+        expected = pd.DataFrame([pd.Timedelta('365d')])
+        result = pd.DataFrame([pd.Timestamp('2018')]) - other
+        tm.assert_frame_equal(expected, result)
+
     @pytest.mark.parametrize('data', [
         [1, 2, 3],
         [1.1, 2.2, 3.3],