Python爬虫开发【第1篇】【多线程爬虫及案例】

糗事百科爬虫实例：

地址：http://www.qiushibaike.com/8hr/page/1

需求：

使用requests获取页面信息，用XPath / re 做数据提取
获取每个帖子里的用户头像链接、用户姓名、段子内容、点赞次数和评论次数
保存到 json 文件内

#qiushibaike.py

#import urllib

#import re

#import chardet

import requests

from lxml import etree

page = 1

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'}

try:

    response = requests.get(url, headers=headers)

    resHtml = response.text

    html = etree.HTML(resHtml)

    result = html.xpath('//div[contains(@id,"qiushi_tag")]')

    for site in result:

        item = {}

        imgUrl = site.xpath('./div/a/img/@src')[0].encode('utf-8')

        username = site.xpath('./div/a/@title')[0].encode('utf-8')

        #username = site.xpath('.//h2')[0].text

        content = site.xpath('.//div[@class="content"]/span')[0].text.strip().encode('utf-8')

        # 投票次数

        vote = site.xpath('.//i')[0].text

        #print site.xpath('.//*[@class="number"]')[0].text

        # 评论信息

        comments = site.xpath('.//i')[1].text

        print imgUrl, username, content, vote, comments

except Exception, e:

    print e

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

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

多线程爬虫示意图：

# -*- 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()

巴特西

Python爬虫开发【第1篇】【多线程爬虫及案例】

糗事百科爬虫实例：

Queue（队列对象）

多线程爬虫示意图：

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