Allowing empty slice in multi-indices.

Author: SylvainCorlay

doc/source/whatsnew/v0.15.2.txt

@@ -44,4 +44,5 @@ Experimental
 Bug Fixes
 ~~~~~~~~~
 - Bug in ``groupby`` signatures that didn't include *args or **kwargs (:issue:`8733`).
-- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo (:issue:`8761`).
+- ``io.data.Options`` now raises ``RemoteDataError`` when no expiry dates are available from Yahoo (:issue:`8761`).
+- Bug in slicing a multi-index with an empty list and at least one boolean indexer (:issue:`8781`)

pandas/core/index.py

@@ -4148,9 +4148,9 @@ def _convert_indexer(r):
                         # ignore not founds
                         continue
                 if len(k):
-                    ranges.append(reduce(np.logical_or,indexers))
+                    ranges.append(reduce(np.logical_or, indexers))
                 else:
-                    ranges.append(tuple([]))
+                    ranges.append(np.zeros(self.labels[i].shape, dtype=bool))
 
             elif _is_null_slice(k):
                 # empty slice

pandas/tests/test_indexing.py

@@ -2139,9 +2139,11 @@ def f():
         df = DataFrame(np.random.randn(5, 6), index=range(5), columns=multi_index)
         df = df.sortlevel(0, axis=1)
 
-        result = df.loc[:, ([], slice(None))]
+        result1 = df.loc[:, ([], slice(None))]
+        result2 = df.loc[:, (['foo'], [])]
         expected = DataFrame(index=range(5),columns=multi_index.reindex([])[0])
-        assert_frame_equal(result, expected)
+        assert_frame_equal(result1, expected)
+        assert_frame_equal(result2, expected)
 
         # regression from < 0.14.0
         # GH 7914