BUG: iloc fails with non lex-sorted MultiIndex #13797

pandas/core/indexing.py

@@ -903,7 +903,9 @@ def _getitem_lowerdim(self, tup):
 
         # we maybe be using a tuple to represent multiple dimensions here
         ax0 = self.obj._get_axis(0)
-        if isinstance(ax0, MultiIndex):
+        # ...but iloc should handle the tuple as simple integer-location
+        # instead of checking it as multiindex representation (GH 13797)
+        if isinstance(ax0, MultiIndex) and self.name != 'iloc':
             result = self._handle_lowerdim_multi_index_axis0(tup)
             if result is not None:
                 return result

pandas/tests/test_multilevel.py

@@ -2420,6 +2420,34 @@ def test_repeat(self):
         m_df = pd.Series(data, index=m_idx)
         assert m_df.repeat(3).shape == (3 * len(data), )
 
+    def test_iloc_mi(self):
+        # GH 13797
+        # Test if iloc can handle integer locations in MultiIndexed DataFrame
+
+        data = [
+            ['str00', 'str01'],
+            ['str10', 'str11'],
+            ['str20', 'srt21'],
+            ['str30', 'str31'],
+            ['str40', 'str41']
+        ]
+
+        mi = pd.MultiIndex.from_tuples(
+            [('CC', 'A'),
+             ('CC', 'B'),
+             ('CC', 'B'),
+             ('BB', 'a'),
+             ('BB', 'b')
+             ])
+
+        ans = pd.DataFrame(data)
+        df_mi = pd.DataFrame(data, index=mi)
+
+        res = pd.DataFrame([[df_mi.iloc[r, c] for c in range(2)]
+                            for r in range(5)])
+
+        assert_frame_equal(res, ans)
+
 
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],