ENH: _dir_additions returns also the first level of a MultiIndex

Author: Martin Journois

pandas/core/generic.py

@@ -194,8 +194,10 @@ def __unicode__(self):
         return '%s(%s)' % (self.__class__.__name__, prepr)
 
     def _dir_additions(self):
-        """ add the string-like attributes from the info_axis """
-        additions = set([c for c in self._info_axis
+        """ add the string-like attributes from the info_axis.
+        If info_axis is a MultiIndex, it's first level values are used.
+        """
+        additions = set([c for c in self._info_axis.get_level_values(0)
                          if isinstance(c, string_types) and isidentifier(c)])
         return super(NDFrame, self)._dir_additions().union(additions)