多线程糗事百科案例

案例要求参考上一个糗事百科单进程案例

Queue（队列对象）

Queue是python中的标准库，可以直接import Queue引用;队列是线程间最常用的交换数据的形式

python下多线程的思考

对于资源，加锁是个重要的环节。因为python原生的list,dict等，都是not thread safe的。而Queue，是线程安全的，因此在满足使用条件下，建议使用队列

1. 初始化： class Queue.Queue(maxsize) FIFO 先进先出

2. 包中的常用方法:

   • Queue.qsize() 返回队列的大小

   • Queue.empty() 如果队列为空，返回True,反之False

   • Queue.full() 如果队列满了，返回True,反之False

   • Queue.full 与 maxsize 大小对应

   • Queue.get([block[, timeout]])获取队列，timeout等待时间

3. 创建一个“队列”对象

   • import Queue
   • myqueue = Queue.Queue(maxsize = 10)

4. 将一个值放入队列中

   • myqueue.put(10)

5. 将一个值从队列中取出

   • myqueue.get()

多线程示意图

# -*- coding:utf-8 -*-import requestsfrom lxml import etreefrom Queue import Queueimport threadingimport timeimport jsonclass thread_crawl(threading.Thread):    '''    抓取线程类    '''    def __init__(self, threadID, q):        threading.Thread.__init__(self)        self.threadID = threadID        self.q = q    def run(self):        print "Starting " + self.threadID        self.qiushi_spider()        print "Exiting ", self.threadID    def qiushi_spider(self):        # page = 1        while True:            if self.q.empty():                break            else:                page = self.q.get()                print 'qiushi_spider=', self.threadID, ',page=', str(page)                url = 'http://www.qiushibaike.com/8hr/page/' + str(page) + '/'                headers = {                    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36',                    'Accept-Language': 'zh-CN,zh;q=0.8'}                # 多次尝试失败结束、防止死循环                timeout = 4                while timeout > 0:                    timeout -= 1                    try:                        content = requests.get(url, headers=headers)                        data_queue.put(content.text)                        break                    except Exception, e:                        print 'qiushi_spider', e                if timeout < 0:                    print 'timeout', urlclass Thread_Parser(threading.Thread):    '''    页面解析类；    '''    def __init__(self, threadID, queue, lock, f):        threading.Thread.__init__(self)        self.threadID = threadID        self.queue = queue        self.lock = lock        self.f = f    def run(self):        print 'starting ', self.threadID        global total, exitFlag_Parser        while not exitFlag_Parser:            try:                '''                调用队列对象的get()方法从队头删除并返回一个项目。可选参数为block，默认为True。                如果队列为空且block为True，get()就使调用线程暂停，直至有项目可用。                如果队列为空且block为False，队列将引发Empty异常。                '''                item = self.queue.get(False)                if not item:                    pass                self.parse_data(item)                self.queue.task_done()                print 'Thread_Parser=', self.threadID, ',total=', total            except:                pass        print 'Exiting ', self.threadID    def parse_data(self, item):        '''        解析网页函数        :param item: 网页内容        :return:        '''        global total        try:            html = etree.HTML(item)            result = html.xpath('//div[contains(@id,"qiushi_tag")]')            for site in result:                try:                    imgUrl = site.xpath('.//img/@src')[0]                    title = site.xpath('.//h2')[0].text                    content = site.xpath('.//div[@class="content"]/span')[0].text.strip()                    vote = None                    comments = None                    try:                        vote = site.xpath('.//i')[0].text                        comments = site.xpath('.//i')[1].text                    except:                        pass                    result = {                        'imgUrl': imgUrl,                        'title': title,                        'content': content,                        'vote': vote,                        'comments': comments,                    }                    with self.lock:                        # print 'write %s' % json.dumps(result)                        self.f.write(json.dumps(result, ensure_ascii=False).encode('utf-8') + "\n")                except Exception, e:                    print 'site in result', e        except Exception, e:            print 'parse_data', e        with self.lock:            total += 1data_queue = Queue()exitFlag_Parser = Falselock = threading.Lock()total = 0def main():    output = open('qiushibaike.json', 'a')    #初始化网页页码page从1-10个页面    pageQueue = Queue(50)    for page in range(1, 11):        pageQueue.put(page)    #初始化采集线程    crawlthreads = []    crawlList = ["crawl-1", "crawl-2", "crawl-3"]    for threadID in crawlList:        thread = thread_crawl(threadID, pageQueue)        thread.start()        crawlthreads.append(thread)    #初始化解析线程parserList    parserthreads = []    parserList = ["parser-1", "parser-2", "parser-3"]    #分别启动parserList    for threadID in parserList:        thread = Thread_Parser(threadID, data_queue, lock, output)        thread.start()        parserthreads.append(thread)    # 等待队列清空    while not pageQueue.empty():        pass    # 等待所有线程完成    for t in crawlthreads:        t.join()    while not data_queue.empty():        pass    # 通知线程是时候退出    global exitFlag_Parser    exitFlag_Parser = True    for t in parserthreads:        t.join()    print "Exiting Main Thread"    with lock:        output.close()if __name__ == '__main__':    main()