BUG: Series.align resets name when fill_value is specified

Author: sinhrks

doc/source/whatsnew/v0.16.1.txt

@@ -308,7 +308,7 @@ Bug Fixes
 - Fixed latex output for multi-indexed dataframes (:issue:`9778`)
 - Bug causing an exception when setting an empty range using ``DataFrame.loc`` (:issue:`9596`)
 
-
+- Bug in ``Series.align`` resets ``name`` when ``fill_value`` is specified (:issue:`10067`)
 
 
 - Bug in hiding ticklabels with subplots and shared axes when adding a new plot to an existing grid of axes (:issue:`9158`)

pandas/core/generic.py

@@ -3406,6 +3406,9 @@ def _align_series(self, other, join='outer', axis=None, level=None,
             else:
                 right_result = other.reindex(join_index, level=level)
 
+        left_result = left_result.__finalize__(self)
+        right_result = right_result.__finalize__(other)
+
         # fill
         fill_na = notnull(fill_value) or (method is not None)
         if fill_na:
@@ -3414,8 +3417,7 @@ def _align_series(self, other, join='outer', axis=None, level=None,
                     right_result.fillna(fill_value, method=method,
                                         limit=limit))
         else:
-            return (left_result.__finalize__(self),
-                    right_result.__finalize__(other))
+            return left_result, right_result
 
     _shared_docs['where'] = ("""
         Return an object of same shape as self and whose corresponding

pandas/tests/test_series.py

@@ -5921,19 +5921,26 @@ def _check_align(a, b, how='left', fill=None):
 
             assert_series_equal(aa, ea)
             assert_series_equal(ab, eb)
+            self.assertEqual(aa.name, 'ts')
+            self.assertEqual(ea.name, 'ts')
+            self.assertEqual(ab.name, 'ts')
+            self.assertEqual(eb.name, 'ts')
 
         for kind in JOIN_TYPES:
             _check_align(self.ts[2:], self.ts[:-5], how=kind)
             _check_align(self.ts[2:], self.ts[:-5], how=kind, fill=-1)
 
             # empty left
             _check_align(self.ts[:0], self.ts[:-5], how=kind)
+            _check_align(self.ts[:0], self.ts[:-5], how=kind, fill=-1)
 
             # empty right
             _check_align(self.ts[:-5], self.ts[:0], how=kind)
+            _check_align(self.ts[:-5], self.ts[:0], how=kind, fill=-1)
 
             # both empty
             _check_align(self.ts[:0], self.ts[:0], how=kind)
+            _check_align(self.ts[:0], self.ts[:0], how=kind, fill=-1)
 
     def test_align_fill_method(self):
         def _check_align(a, b, how='left', method='pad', limit=None):