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

added comments and modified test code

Author: ygriku

pandas/core/indexing.py

@@ -903,6 +903,8 @@ def _getitem_lowerdim(self, tup):
 
         # we maybe be using a tuple to represent multiple dimensions here
         ax0 = self.obj._get_axis(0)
+        # ...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:

pandas/tests/test_multilevel.py

@@ -2422,22 +2422,30 @@ def test_repeat(self):
 
     def test_iloc_mi(self):
         # GH 13797
-
-        ind_nonLex = [
-            ['CC', 'CC', 'CC', 'BB', 'BB'],
-            ['A', 'B', 'B', 'a', 'b']
-        ]
-
-        strCol = pd.DataFrame(
-            ['fooA', 'fooB', 'fooC', 'fooD', 'fooE'])
-
-        dat = np.arange(1, 26).reshape(5, 5)
-        df = pd.concat([strCol, pd.DataFrame(dat)], axis=1)
-        df1 = pd.DataFrame(df.values, index=ind_nonLex)
-
-        assert df1.iloc[0, 0] == 'fooA'
-        assert df1.iloc[4, 0] == 'fooE'
-        assert df1.iloc[4, 5] == 25
+        # 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__':