python Queue一般用于哪些方面，这段代码大概是什么流程意思，谢谢

Question

from ccnet.sync_client import SyncClient
import Queue

class ClientPool(object):
    """ccnet client pool."""

    def __init__(self, conf_dir, pool_size=5):
        """
        :param conf_dir: the ccnet configuration directory
        :param pool_size:
        """
        self.conf_dir = conf_dir
        self.pool_size = pool_size
        self._pool = Queue.Queue(pool_size)

    def _create_client(self):
        client = SyncClient(self.conf_dir)
        client.req_ids = {}
        client.connect_daemon()

        return client

    def get_client(self):
        try:
            client = self._pool.get(False)
        except:
            client = self._create_client()
        return client

    def return_client(self, client):
        try:
            self._pool.put(client, False)
        except Queue.Full:
            pass

class SyncClient(Client):
    '''sync mode client'''
    def __init__(self, config_dir):
        Client.__init__(self, config_dir)
        self._req_id = _REQ_ID_START
        self.mq_req_id = -1

    def disconnect_daemon(self):
        if self.is_connected():
            try:
                self._connfd.close()
            except:
                pass

    def read_response(self):
        packet = read_packet(self._connfd)
        if packet.header.ptype != CCNET_MSG_RESPONSE:
            raise RuntimeError('Invalid Response')

        code, code_msg, content = parse_response(packet.body)

        return Response(code, code_msg, content)

    def send_cmd(self, cmd):
        req_id = self.get_request_id()
        self.send_request(req_id, 'receive-cmd')
        resp = self.read_response()
        if resp.code != '200':
            raise RuntimeError('Failed to send-cmd: %s %s' % (resp.code, resp.code_msg))

        cmd += '\000'
        self.send_update(req_id, '200', '', cmd)

        resp = self.read_response()
        if resp.code != '200':
            raise RuntimeError('Failed to send-cmd: %s %s' % (resp.code, resp.code_msg))

        self.send_update(req_id, SC_PROC_DONE, SS_PROC_DONE, '')

    def prepare_recv_message(self, msg_type):
        request = 'mq-server %s' % msg_type
        req_id = self.get_request_id()
        self.send_request(req_id, request)

        resp = self.read_response()
        if resp.code != '200':
            raise RuntimeError('bad response: %s %s' % (resp.code, resp.code_msg))

    def receive_message(self):
        resp = self.read_response()
        # the message from ccnet daemon has the trailing null byte included
        msg = message_from_string(resp.content[:-1])
        return msg

    def prepare_send_message(self):
        request = 'mq-server'
        mq_req_id = self.get_request_id()
        self.send_request(mq_req_id, request)
        resp = self.read_response()
        if resp.code != '200':
            raise RuntimeError('bad response: %s %s' % (resp.code, resp.code_msg))
        self.mq_req_id = mq_req_id

    def send_message(self, msg_type, content):
        if self.mq_req_id == -1:
            self.prepare_send_message()

        msg = gen_inner_message_string(self.peer_id, msg_type, content)
        self.send_update(self.mq_req_id, "300", '', msg)
        resp = self.read_response()
        if resp.code != '200':
            self.mq_req_id = -1
            raise RuntimeError('bad response: %s %s' % (resp.code, resp.code_msg))

    def register_service_sync(self, service, group):
        '''Mainly used by a program to register a dummy service to ensure only
        single instance of that program is running

        '''
        cmd = 'register-service %s %s' % (service, group)
        self.send_cmd(cmd)

Answer 1

Queue 这个数据结构我比较少用，不过查阅了一下 Python 的說明文件：

The Queue module implements multi-producer, multi-consumer queues. It is especially useful in threaded programming when information must be exchanged safely between multiple 完成 when information class i. ilability of thread support in Python; see the threading module.

文件中說明這是一個執行緒安全的佇列，所以可以用在多生產者多消費者的競態環境中，常見於多執行緒程式設計中。

這就是我對 Queue 的理解，现在说会问题中的代码，这段代码从名字上可以比较清晰得看出是一个客户端的池，当你需要获得一个客户端的时候，调用get_client()方法，它会返回一个SyncClient客户端给你，当你用完之后，别忘了调用：return_client(client)換回來，不然，就會產生一大波的客戶端，這裡這麼設計應該是創建大量客戶端是會有問題的。

大概就這些了，不知道題主理解了沒。

Answer 2

Queue是一個線程安全的隊列, 至於給出的代碼, @yylucifer解釋的比較清楚了,其實就是一個可復用的client池. 這種用法很常見, 可以看redis-py的池子設計, blockconnectionpool那個, 基本都是這個思路.