python开发简单爬虫：实战篇

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python开发简单爬虫：实战篇

1. 分析目标

　　本次实战篇的目的是抓取百度百科python词条页面的标题和简介以及与之相关联的词条页面的标题和简介。

目标：百度百科python词条以及相关词条网页的标题和简介
入口页：百度百科python词条页：http://baike.baidu.com/view/21087.htm
url格式：
- 词条页面url：/view/123.htm
数据格式：
- 标题：<dd class="lemmaWgt-lemmaTitle-title"><h1>******</h1></dd>
- 简介：<div class="lemma-summary" label-module="lemmaSummary">******</div>
页面编码：UTF-8

2.URL管理器

代码如下：

# coding:utf8class UrlManager(object):    def __init__(self):        # 初始化待爬取url集合和已爬取url集合        self.new_urls = set()        self.old_urls = set()    # 添加一个新的url到new_urls    def add_new_url(self, url):        if url is None:            return        if url not in self.new_urls and url not in self.old_urls:            self.new_urls.add(url)    # 获取一个待爬取的url,并将此url添加到old_urls    def get_new_url(self):        new_url = self.new_urls.pop()        self.old_urls.add(new_url)        return new_url    # 判断是否还有待爬取的url    def has_new_url(self):        return len(self.new_urls) != 0    # 添加多个url到new_urls    def add_new_urls(self, urls):        if urls is None or len(urls) == 0:            return        for url in urls:            self.add_new_url(url)

3. 网页下载器

代码如下：

# coding:utf8import urllib2class HtmlDownloader(object):    # 使用urllib2最简单的方法下载url页面内容    def download(self, url):        if url is None:            return None        resp = urllib2.urlopen(url)        if resp.getcode() != 200:            return None        return resp.read()

4. 网页解析器

代码如下：

# coding:utf8import reimport urlparsefrom bs4 import BeautifulSoupclass HtmlParser(object):    # 得到页面相关的url    def _get_new_urls(self, page_url, soup):        new_urls = set()        # /view/123.htm        links = soup.find_all('a', href=re.compile(r'/view/\d+\.htm'))        for link in links:            new_url = link['href']            # 将/view/123.htm补充完整：http://baike.baidu.com/view/123.htm            new_full_url = urlparse.urljoin(page_url, new_url)            # 将解析到的unicode编码的网址转化为utf-8格式            new_urls.add(new_full_url.encode('utf-8'))        return new_urls    # 得到页面标题和简介    def _get_new_data(self, page_url, soup):        res_data = {}        # url        res_data['url'] = page_url        # 得到标题节点        # <dd class="lemmaWgt-lemmaTitle-title"> <h1 >Python</h1>        title_node = soup.find('dd', class_='lemmaWgt-lemmaTitle-title').find('h1')        res_data['title'] = title_node.get_text()        # 得到简介节点        # <div class="lemma-summary" label-module="lemmaSummary">        summary_node = soup.find('div', class_='lemma-summary')        res_data['summary'] = summary_node.get_text()        return res_data    # 对下载页面内容进行解析    def parse(self, page_url, html_cont):        if page_url is None or html_cont is None:            return None        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

5. 数据输出器

代码如下：

# coding:utf8class HtmlOutputer(object):    def __init__(self):        self.datas = []    # 收集数据    def collect_data(self, data):        if data is None:            return None        self.datas.append(data)    # 将收集到的数据生成一个HTML页面输出    def output_html(self):        fout = open('output.html', 'w')        fout.write('<html>')        fout.write('<head>')        fout.write('<meta charset="UTF-8"></meta>')        fout.write('</head>')        fout.write('<body>')        fout.write('<table>')        for data in self.datas:            fout.write('<tr>')            fout.write('<td>%s</td>' % data['url'].encode('utf-8'))            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()

6. 爬虫调度器

# coding:utf8from baike1 import url_manager, html_downloader, html_parser, html_outputerclass 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, url):        count = 1        self.urls.add_new_url(url)        while self.urls.has_new_url():            try:                new_url = self.urls.get_new_url()                print 'craw %d：%s' % (count, new_url)                html_cont = self.downloader.download(new_url)                new_urls, new_data = self.parser.parse(new_url, html_cont)                self.urls.add_new_urls(new_urls)                self.outputer.collect_data(new_data)                if count == 100:                    break                count += 1            except:                print 'craw failed'        self.outputer.output_html()if __name__ == "__main__":    root_url = 'http://baike.baidu.com/view/21087.htm'    obj_spider = SpiderMain()    obj_spider.craw(root_url)

程序运行结果截图：
这里写图片描述
至此，一个非常简单的爬虫已经完成，撒花！

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