import operator


def _ext_proc_tpls_to_procs(xps):
    """List processors by each priority.

    :param xps: A list of (file_extension, processor_cls)
    :return: List of [processor_cls]
    """
    return sorted((operator.itemgetter(1)(xp) for xp in xps),
                  key=operator.methodcaller("priority"))