BUG: allow MultiIndex setops with all length-0 indexes close pandas-dev#1727

Author: wesm

RELEASE.rst

@@ -83,6 +83,7 @@ pandas 0.8.2
   - Fix re: unicode MultiIndex level names in Series/DataFrame repr (#1736)
   - Handle PeriodIndex in to_datetime instance method (#1703)
   - Support StaticTzInfo in DatetimeIndex infrastructure (#1692)
+  - Allow MultiIndex setops with length-0 other type indexes (#1727)
 
 pandas 0.8.1
 ============

pandas/core/index.py

@@ -2285,6 +2285,8 @@ def diff(self, other):
 
     def _assert_can_do_setop(self, other):
         if not isinstance(other, MultiIndex):
+            if len(other) == 0:
+                return True
             raise TypeError('can only call with other hierarchical '
                             'index objects')
 

pandas/tests/test_multilevel.py

@@ -1432,6 +1432,18 @@ def test_set_column_scalar_with_ix(self):
         col[subset] = 97
         self.assert_((self.frame.ix[subset, 'B'] == 97).all())
 
+    def test_frame_dict_constructor_empty_series(self):
+        s1 = Series([1,2,3, 4], index=MultiIndex.from_tuples([(1,2),(1,3),
+                                                              (2,2),(2,4)]))
+        s2 = Series([1,2,3,4],
+                    index=MultiIndex.from_tuples([(1,2),(1,3),(3,2),(3,4)]))
+        s3 = Series()
+
+        # it works!
+        df = DataFrame({'foo':s1, 'bar':s2, 'baz':s3})
+        df = DataFrame.from_dict({'foo':s1, 'baz':s3, 'bar':s2})
+
+
 if __name__ == '__main__':
 
     # unittest.main()