ENH: _dir_additions returns also the first level of a MultiIndex

Author: Martin Journois

pandas/core/generic.py

@@ -195,7 +195,11 @@ def __unicode__(self):
     def _dir_additions(self):
         """ add the string-like attributes from the info_axis """
         additions = set([c for c in self._info_axis
-                         if isinstance(c, string_types) and isidentifier(c)])
+                         if isinstance(c, string_types) and isidentifier(c)] +
+                        [c[0] for c in self._info_axis
+                         if isinstance(c, tuple) and
+                         isinstance(c[0], string_types) and
+                         isidentifier(c[0])])
         return super(NDFrame, self)._dir_additions().union(additions)
 
     @property