def ports_from_output_port_acts(output_port_acts):
    """Return unique port numbers from OFPActionOutput actions.

    Args:
        list of ryu.ofproto.ofproto_v1_3_parser.OFPActionOutput: output to port actions.
    Returns:
        set of port number ints.
    """
    return {output_port_act.port for output_port_act in output_port_acts}