BUG: fix indexing ambiguity with MultiIndex close pandas-dev#1678

Author: wesm

RELEASE.rst

@@ -87,6 +87,7 @@ pandas 0.8.2
   - Allow MultiIndex setops with length-0 other type indexes (#1727)
   - Fix handling of DatetimeIndex in DataFrame.to_records (#1720)
   - Fix handling of general objects in isnull on which bool(...) fails (#1749)
+  - Fix .ix indexing with MultiIndex ambiguity (#1678)
 
 pandas 0.8.1
 ============

pandas/core/indexing.py

@@ -35,6 +35,12 @@ def __getitem__(self, key):
             return self._getitem_axis(key, axis=0)
 
     def _get_label(self, label, axis=0):
+        # ueber-hack
+        if (isinstance(label, tuple) and
+            isinstance(label[axis], slice)):
+
+            raise IndexingError('no slices here')
+
         try:
             return self.obj.xs(label, axis=axis, copy=False)
         except Exception:

pandas/tests/test_multilevel.py

@@ -1443,6 +1443,18 @@ def test_frame_dict_constructor_empty_series(self):
         df = DataFrame({'foo':s1, 'bar':s2, 'baz':s3})
         df = DataFrame.from_dict({'foo':s1, 'baz':s3, 'bar':s2})
 
+    def test_indexing_ambiguity_bug_1678(self):
+        columns = MultiIndex.from_tuples([('Ohio', 'Green'), ('Ohio', 'Red'),
+                                          ('Colorado', 'Green')])
+        index = MultiIndex.from_tuples([('a', 1), ('a', 2), ('b', 1), ('b', 2)])
+
+        frame = DataFrame(np.arange(12).reshape((4, 3)), index=index,
+                          columns=columns)
+
+        result = frame.ix[:, 1]
+        exp = frame.icol(1)
+        self.assert_(isinstance(result, Series))
+        assert_series_equal(result, exp)
 
 if __name__ == '__main__':
 

pandas/tests/test_panel.py

@@ -1087,7 +1087,7 @@ def test_from_frame_level1_unsorted(self):
         midx = MultiIndex.from_tuples(tuples)
         df = DataFrame(np.random.rand(5,4), index=midx)
         p = df.to_panel()
-        assert_frame_equal(p.minor_xs(2), df.ix[:,2].sort_index())
+        assert_frame_equal(p.minor_xs(2), df.xs(2, level=1).sort_index())
 
     def test_to_excel(self):
         try: