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
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初始化： class Queue.Queue(maxsize) FIFO 先进先出
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包中的常用方法:
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Queue.qsize() 返回队列的大小
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Queue.empty() 如果队列为空，返回True,反之False
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Queue.full() 如果队列满了，返回True,反之False
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Queue.full 与 maxsize 大小对应
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Queue.get([block[, timeout]])获取队列，timeout等待时间
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创建一个“队列”对象
- import Queue
- myqueue = Queue.Queue(maxsize = 10)
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将一个值放入队列中
- myqueue.put(10)
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将一个值从队列中取出
- myqueue.get()
多线程示意图
# -*- coding:utf-8 -*-
import requests
from lxml import etree
from Queue import Queue import threading import time import json class 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', url class 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 += 1 data_queue = Queue() exitFlag_Parser = False lock = threading.Lock() total = 0 def 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()
