BUG: Bug in multi-index slice setting, related GH3738

pandas/core/index.py

@@ -523,6 +523,10 @@ def _convert_slice_indexer_getitem(self, key, is_index_slice=False):
     def _convert_slice_indexer(self, key, typ=None):
         """ convert a slice indexer. disallow floats in the start/stop/step """
 
+        # if we are not a slice, then we are done
+        if not isinstance(key, slice):
+            return key
+
         # validate iloc
         if typ == 'iloc':
 
@@ -2008,6 +2012,11 @@ def _convert_scalar_indexer(self, key, typ=None):
     def _convert_slice_indexer(self, key, typ=None):
         """ convert a slice indexer, by definition these are labels
             unless we are iloc """
+
+        # if we are not a slice, then we are done
+        if not isinstance(key, slice):
+            return key
+
         if typ == 'iloc':
             return super(Float64Index, self)._convert_slice_indexer(key,
                                                                     typ=typ)

pandas/tests/test_indexing.py

@@ -1883,6 +1883,29 @@ def f():
             df.loc['bar'] *= 2
         self.assertRaises(TypeError, f)
 
+        # from SO
+        #http://stackoverflow.com/questions/24572040/pandas-access-the-level-of-multiindex-for-inplace-operation
+        df_orig = DataFrame.from_dict({'price': {
+            ('DE', 'Coal', 'Stock'): 2,
+            ('DE', 'Gas', 'Stock'): 4,
+            ('DE', 'Elec', 'Demand'): 1,
+            ('FR', 'Gas', 'Stock'): 5,
+            ('FR', 'Solar', 'SupIm'): 0,
+            ('FR', 'Wind', 'SupIm'): 0}})
+        df_orig.index = MultiIndex.from_tuples(df_orig.index, names=['Sit', 'Com', 'Type'])
+
+        expected = df_orig.copy()
+        expected.iloc[[0,2,3]] *= 2
+
+        idx = pd.IndexSlice
+        df = df_orig.copy()
+        df.loc[idx[:,:,'Stock'],:] *= 2
+        assert_frame_equal(df, expected)
+
+        df = df_orig.copy()
+        df.loc[idx[:,:,'Stock'],'price'] *= 2
+        assert_frame_equal(df, expected)
+
     def test_getitem_multiindex(self):
 
         # GH 5725