'Delete one or more elements of the spinbox.
First is the index of the first character to delete,
and last is the index of the character just after
the last one to delete. If last isn\'t specified it
defaults to first+1, i.e. a single character is
deleted.  This command returns an empty string.'

def delete(self, first, last=None):

    return self.tk.call(self._w, 'delete', first, last)
