BUG: Fix GH15155

Author: watercrossing

pandas/indexes/category.py

@@ -255,6 +255,9 @@ def categories(self):
     def ordered(self):
         return self._data.ordered
 
+    def _reverse_indexer(self):
+        return self._data._reverse_indexer()
+
     def __contains__(self, key):
         hash(key)
         return key in self.values

pandas/tests/groupby/test_categorical.py

@@ -9,8 +9,8 @@
 
 from pandas.core.series import Series
 
-from pandas.util.testing import (assert_frame_equal, assert_series_equal
-                                 )
+from pandas.util.testing import (assert_frame_equal, assert_series_equal,
+                                 assert_numpy_array_equal)
 
 from pandas.compat import (lmap)
 
@@ -48,8 +48,9 @@ def setUp(self):
              'D': np.array(
                  np.random.randn(8), dtype='float32')})
 
-        index = MultiIndex(levels=[['foo', 'bar', 'baz', 'qux'], ['one', 'two',
-                                                                  'three']],
+        index = MultiIndex(levels=[pd.CategoricalIndex(
+                                   ['foo', 'bar', 'baz', 'qux']),
+                                   ['one', 'two', 'three']],
                            labels=[[0, 0, 0, 1, 1, 2, 2, 3, 3, 3],
                                    [0, 1, 2, 0, 1, 1, 2, 0, 1, 2]],
                            names=['first', 'second'])
@@ -67,6 +68,12 @@ def setUp(self):
              'E': np.random.randn(11),
              'F': np.random.randn(11)})
 
+    def test_level_groupby_get_group(self):
+        # gh15155
+        testGroupBy = self.mframe.groupby(level=["first"])
+        assert_numpy_array_equal(testGroupBy.get_group("foo").values,
+                                 self.mframe.loc["foo"].values)
+
     def test_apply_use_categorical_name(self):
         from pandas import qcut
         cats = qcut(self.df.C, 4)