BUG: MultiIndex.sortlevel did not preserve names GH #202

Author: wesm

RELEASE.rst

@@ -5,6 +5,21 @@ Release Notes
 This is the list of changes to pandas between each release. For full details,
 see the commit logs at http://github.com/wesm/pandas
 
+pandas 0.4.3
+============
+
+**Release date:** not yet released
+
+**Improvements to existing features**
+
+  - Skip xlrd-related unit tests if not installed
+
+**Bug fixes**
+
+  - Fix broken interaction between `Index` and `Int64Index` when calling
+    intersection. Implement `Int64Index.intersection`
+  - `MultiIndex.sortlevel` discarded the level names (GH #202)
+
 pandas 0.4.2
 ============
 

pandas/core/index.py

@@ -1120,7 +1120,7 @@ def sortlevel(self, level=0, ascending=True):
 
         new_labels = [lab.take(indexer) for lab in self.labels]
         new_index = MultiIndex(levels=self.levels, labels=new_labels,
-                               sortorder=level)
+                               names=self.names, sortorder=level)
 
         return new_index, indexer
 

pandas/tests/test_multilevel.py

@@ -24,7 +24,8 @@ def setUp(self):
         index = MultiIndex(levels=[['foo', 'bar', 'baz', 'qux'],
                                    ['one', 'two', 'three']],
                            labels=[[0, 0, 0, 1, 1, 2, 2, 3, 3, 3],
-                                   [0, 1, 2, 0, 1, 1, 2, 0, 1, 2]])
+                                   [0, 1, 2, 0, 1, 1, 2, 0, 1, 2]],
+                           names=['first', 'second'])
         self.frame = DataFrame(np.random.randn(10, 3), index=index,
                                columns=['A', 'B', 'C'])
 
@@ -220,6 +221,9 @@ def test_sortlevel(self):
         self.assertRaises(Exception,
                           self.frame.delevel()['A'].sortlevel)
 
+        # preserve names
+        self.assertEquals(a_sorted.index.names, self.frame.index.names)
+
     def test_sortlevel_by_name(self):
         self.frame.index.names = ['first', 'second']
         result = self.frame.sortlevel(level='second')