ENH: _dir_additions returns also the first level of a MultiIndex

Author: Martin Journois

pandas/core/generic.py

@@ -190,7 +190,11 @@ def __unicode__(self):
     def _dir_additions(self):
         """ add the string-like attributes from the info_axis """
         return 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])])
 
     @property
     def _constructor_sliced(self):