def iterpws(self, n):
        """
        Returns passwords in order of their frequencies.
        @n: The numebr of passwords to return
        Return: pwid, password, frequency
        Every password is assigned an uniq id, for efficient access.
        """
        for _id in np.argsort(self._freq_list)[::-1][:n]:
            pw = self._T.restore_key(_id)
            if self._min_pass_len <= len(pw) <= self._max_pass_len:
                yield _id, pw, self._freq_list[_id]