class ThreadUrl(threading.Thread):
    def __init__(self, main_queue, source1_queue, source2_queue, source3_queue, source4_queue):
        threading.Thread.__init__(self)
        self.main_queue = main_queue
        self.source1_queue = source1_queue
        self.source2_queue = source2_queue
        self.source3_queue = source3_queue
        self.source4_queue = source4_queue

    def run(self):
        while True:
            # 从任务队列里取出任务
            sql_dict = self.main_queue.get()

            sql = sql_dict.get('a')
            if sql is not None:
                self.source1_queue.put(sql)
                self.main_queue.task_done()
            else:
                sql = sql_dict.get('b')
                if sql is not None:
                    self.source2_queue.put(sql)
                    self.main_queue.task_done()
                else:
                    sql = sql_dict.get('c')
                    if sql is not None:
                        self.source3_queue.put(sql)
                        self.main_queue.task_done()
                    else:
                        sql = sql_dict.get('d')
                        if sql is not None:
                            self.source4_queue.put(sql)
                            self.main_queue.task_done()

类似这种形式。