BUG: fix scalar setting via ix with MultiIndex, GH #551

RELEASE.rst

@@ -110,6 +110,11 @@ pandas 0.6.2
   - Handle all NA case in Series.corr, was raising exception (GH #548)
   - Aggregating by multiple levels with ``level`` argument to DataFrame, Series
     stat method, was broken (GH #545)
+  - Fix Cython buf when converter passed to read_csv produced a numeric array
+    (buffer dtype mismatch when passed to Cython type inference function) (GH
+    #546)
+  - Fix exception when setting scalar value using .ix on a DataFrame with a
+    MultiIndex (GH #551)
 
 Thanks
 ------

pandas/core/indexing.py

@@ -211,6 +211,12 @@ def _convert_to_indexer(self, obj, axis=0):
         - No, prefer label-based indexing
         """
         index = self.obj._get_axis(axis)
+
+        try:
+            return index.get_loc(obj)
+        except (KeyError, TypeError):
+            pass
+
         is_int_index = _is_integer_index(index)
         if isinstance(obj, slice):
             if _is_label_slice(index, obj):

pandas/tests/test_multilevel.py

@@ -290,6 +290,16 @@ def test_setitem_change_dtype(self):
         reindexed = dft.reindex(columns=[('foo', 'two')])
         assert_series_equal(reindexed['foo', 'two'], s > s.median())
 
+    def test_frame_setitem_ix(self):
+        self.frame.ix[('bar', 'two'), 'B'] = 5
+        self.assertEquals(self.frame.ix[('bar', 'two'), 'B'], 5)
+
+        # with integer labels
+        df = self.frame.copy()
+        df.columns = range(3)
+        df.ix[('bar', 'two'), 1] = 7
+        self.assertEquals(df.ix[('bar', 'two'), 1], 7)
+
     def test_fancy_slice_partial(self):
         result = self.frame.ix['bar':'baz']
         expected = self.frame[3:7]