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:http://www.cnblogs.com/miqi1992/p/8081929.html
Queue(队列对象)
Queue是python中的标准库，可以直接import Queue引用；队列时线程间最常用的交互数据的形式。
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
- 初始化：class Queue.Queue(maxsize)FIFO先进先出
- 包中的常用方法：
- Queue.qszie()返回队列的大小
- Queue.empty()如果队列为空，返回True，否则返回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等待事件
- 创建一个"队列"对象
- import Queue
- myqueue = Queue.Queue(maxsize=10)
- 将一个值放入队列中
- myqueue.put(10)
- 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("String: "+self.threadID) self.qiushi_spider() print("Exiting: "+self.threadID) def qiushi_spider(self): 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: # 投票次数 vote = site.xpath('.//i')[0].text # print(vote) #print site.xpath('.//*[@class="number"]')[0].text # 评论信息 comments = site.xpath('.//i')[1].text except: pass result = { 'imageUrl' : imgUrl, 'title' : title, 'content' : content, 'vote' : vote, 'comments' : comments } with self.lock: 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(10) 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parseList 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) # 等待队列情况 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()