ENH: more helpful error message when nothing passed to reindex, close #1267

Author: wesm

RELEASE.rst

@@ -74,6 +74,7 @@ pandas 0.8.0
   - Add histogram / kde plot options for scatter_matrix diagonals (#1237)
   - Add inplace option to Series/DataFrame.rename and sort_index,
     DataFrame.drop_duplicates (#805, #207)
+  - More helpful error message when nothing passed to Series.reindex (#1267)
 
 **API Changes**
 

pandas/core/series.py

@@ -1983,6 +1983,9 @@ def reindex(self, index=None, method=None, level=None, fill_value=np.nan,
         -------
         reindexed : Series
         """
+        if index is None:
+            raise ValueError('Must pass Index or sequence, not None')
+
         index = _ensure_index(index)
         if self.index.equals(index):
             if copy:

pandas/tests/test_series.py

@@ -2236,6 +2236,8 @@ def test_reindex(self):
         for idx, val in subNonContig.iteritems():
             self.assertEqual(val, self.ts[idx])
 
+        self.assertRaises(ValueError, self.ts.reindex)
+
     def test_reindex_corner(self):
         # (don't forget to fix this) I think it's fixed
         reindexed_dep = self.empty.reindex(self.ts.index, method='pad')