python开发简单爬虫：实战篇

最新推荐文章于 2023-04-24 15:48:02 发布

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#python #url #爬虫 #百度 #数据

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本文介绍了一个简单的Python爬虫实战案例，旨在抓取百度百科中Python词条及其相关词条的标题和简介，并通过解析网页内容实现数据的自动收集。

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:utf8
class 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:utf8
import urllib2

class 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:utf8
import re
import urlparse

from bs4 import BeautifulSoup

class 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:utf8
class 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:utf8

from baike1 import url_manager, html_downloader, html_parser, html_outputer

class 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)