fix where

Author: jreback

pandas/core/internals.py

@@ -476,6 +476,8 @@ def _maybe_downcast(self, blocks, downcast=None):
         elif downcast is None and (self.is_timedelta or self.is_datetime):
             return blocks
 
+        if not isinstance(blocks, list):
+            blocks = [blocks]
         return _extend_blocks([b.downcast(downcast) for b in blocks])
 
     def downcast(self, dtypes=None, mgr=None):
@@ -1437,13 +1439,15 @@ def func(cond, values, other):
         try:
             result = func(cond, values, other)
         except TypeError:
+
             # we cannot coerce, return a compat dtype
             # we are explicity ignoring raise_on_error here
             block = self.coerce_to_target_dtype(other)
-            return block.where(orig_other, cond, align=align,
-                               raise_on_error=raise_on_error,
-                               try_cast=try_cast, axis=axis,
-                               transpose=transpose)
+            blocks = block.where(orig_other, cond, align=align,
+                                 raise_on_error=raise_on_error,
+                                 try_cast=try_cast, axis=axis,
+                                 transpose=transpose)
+            return self._maybe_downcast(blocks, 'infer')
 
         if self._can_hold_na or self.ndim == 1:
 

pandas/tests/frame/test_indexing.py

@@ -2712,7 +2712,7 @@ def test_where_axis(self):
         result.where(mask, s, axis='index', inplace=True)
         assert_frame_equal(result, expected)
 
-        expected = DataFrame([[0, np.nan], [0, np.nan]], dtype='float64')
+        expected = DataFrame([[0, np.nan], [0, np.nan]])
         result = df.where(mask, s, axis='columns')
         assert_frame_equal(result, expected)
 

pandas/tests/series/test_indexing.py

@@ -1377,7 +1377,7 @@ def test_where_dups(self):
 
     def test_where_datetime_conversion(self):
         s = Series(date_range('20130102', periods=2))
-        expected = Series([10, 10], dtype='object')
+        expected = Series([10, 10])
         mask = np.array([False, False])
 
         rs = s.where(mask, [10, 10])
@@ -1406,7 +1406,7 @@ def test_where_datetime_conversion(self):
 
     def test_where_timedelta_coerce(self):
         s = Series([1, 2], dtype='timedelta64[ns]')
-        expected = Series([10, 10], dtype='object')
+        expected = Series([10, 10])
         mask = np.array([False, False])
 
         rs = s.where(mask, [10, 10])