gistfile1.txt

MYCONST = ('new_val', 'New Label')


class Partner(osv.osv):
    """My Stuff"""
    _inherit = 'res.partner'

    def __init__(self, pool, cursor):
        """Hack due to the lack of selection fields inheritance mechanism."""
        super(Partner, self).__init__(pool, cursor)
        my_selection = self._columns['my_selection'].selection
        if MYCONST not in my_selection:
            my_selection.append(MYCONST)

in pg84-next (already)

class partner(osv.osv):
_inherit = 'res.partner'
_columns = {
'my_selection': fields.inherit(selection_extend=[('new_val', 'New Label')])
}