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Python爬虫实战糗事百科实例

爬取糗事百科段子,假设页面的URL是 http://www.qiushibaike.com/8hr/page/1

要求:

  1. 使用requests获取页面信息,用XPath / re 做数据提取

  2. 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评论次数

  3. 保存到 json 文件内

参考代码

#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

演示效果

 

多线程糗事百科案例

案例要求参考上面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 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()

 

 

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