python最简单的爬虫

来源：互联网发布：小企业会计记账软件编辑：程序博客网时间：2024/06/05 20:01

主要5部分：主函数，url管理器，网页下载器，网页输出器，网页解析器

（用了set，但是下面的代码并没有突出set的优势。后续可改进）

主要入口函数， spider_main:

import url_manager, html_downloader, html_outputer, html_parserclass SpiderMain(object):    def __init__(self):        self.urls = url_manager.UrlManager()        self.downloader = html_downloader.HtmlDownloader()        self.parser = html_parser.HtmlParser()        self.outputer = html_outputer.HtmlOutputer()    def craw(self, root_url):        count = 1        self.urls.add_new_url(root_url)#根节点入队        while self.urls.has_new_url():#类似广度优先搜索            try:                new_url = self.urls.get_new_url()#从队列中得到一个新的url                print 'craw %d : %s' % (count, new_url)#哪个url正在被爬取                html_cont = self.downloader.download(new_url)#把这个网页爬下来                new_urls, new_data = self.parser.parse(new_url, html_cont)#解析内部的url和数据                self.urls.add_new_urls(new_urls)#将又爬到的url添加到队列中                self.outputer.collect_data(new_data)#收集数据                self.outputer.output_html()#打印数据                if count == 10:                    break                count += 1            except Exception as e:                print e                print 'craw failed'if __name__ == "__main__":    root_url = "http://baike.baidu.com/view/21087.htm" #根节点    obj_spider = SpiderMain()    obj_spider.craw(root_url)

url管理器：

class UrlManager(object):    def __init__(self):        self.new_urls = set()        self.old_urls = set()    def get_new_url(self):        new_url = self.new_urls.pop()        self.old_urls.add(new_url)        return new_url    def add_new_url(self, url):#添加新的url到队列中        if url is None:            return        if url not in self.new_urls and url not in self.old_urls:            self.new_urls.add(url)    def add_new_urls(self, urls):#批量添加        if urls is None or len(urls) == 0:#没爬到或者爬到了空串            return        for url in urls:            self.add_new_url(url)    def has_new_url(self):#判断队列是否为空        return len(self.new_urls) != 0

网页下载器：

import urllib2class HtmlDownloader(object):    def download(self, url):        if url is None:            return None        response = urllib2.urlopen(url)#打开url，并获取返回值        if response.getcode() != 200:            return None        return response.read()#返回网页的全部内容

网页解析器：

import reimport urlparsefrom bs4 import BeautifulSoupclass HtmlParser(object):    def _get_new_urls(self, page_url, soup):#从一堆文字中获取url（正则匹配）        new_urls = set()        links = soup.find_all('a', href = re.compile(r"/view/\d+\.htm"))#获取a标签中，href为指定格式的标签全部内容        for link in links:            new_url = link['href']#取其中的href            new_full_url = urlparse.urljoin(page_url, new_url)#拼接成完整链接            new_urls.add(new_full_url)        return new_urls    def _get_new_data(self, page_url, soup):#从一堆文字中获取数据        res_data = {}#键值对组合，title键值对，summary键值对        #url        res_data['url'] = page_url        #<dd class="lemmaWgt-lemmaTitle-title">        title_node = soup.find('dd', class_ = "lemmaWgt-lemmaTitle-title").find('h1')        res_data['title'] = title_node.get_text()        #print res_data['title']        #<div class="lemma-summary" label-module="lemmaSummary">        summary_node = soup.find('div', class_ = "lemma-summary")        res_data['summary'] = summary_node.get_text()        #print res_data['summary']        return res_data    def parse(self, page_url, html_cont):        if page_url is None or html_cont is None:            return        soup = BeautifulSoup(html_cont, 'html.parser', from_encoding = 'utf-8')        new_urls = self._get_new_urls(page_url, soup)        new_data = self._get_new_data(page_url, soup)        return new_urls, new_data

网页输出器：

class HtmlOutputer(object):    def __init__(self):        self.datas = []    def collect_data(self, data):#将数据（键值对们）组成列表        if data is None:            return        self.datas.append(data)    def output_html(self):        fout = open("F:\\output.html", 'w')        fout.write("<html>")        fout.write("<body>")        fout.write("<table>")        for data in self.datas:            print data['title']            fout.write("<tr>")            fout.write("<td>%s</td>" % data['url'])            fout.write("<td>%s</td>" % data['title'].encode('utf-8'))            fout.write("<td>%s</td>" % data['summary'].encode('utf-8'))            fout.write("</tr>")        fout.write("</table>")        fout.write("</body>")        fout.write("</html>")        fout.close()

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