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Python实现简单爬虫

高洛峰original: 2016-12-13 13:53:391432parcourir

简介

爬虫是一段自动抓取互联网信息的程序。它的价值是互联网数据为我所有。利用爬取到的数据，可以做很多的事情如：可以进行数据统计，对比；可以利用爬取的数据做某一方面的app；也可以利用爬取的数据做一个新闻阅读器等等。

爬虫架构

1）URL管理器
2）网页下载器
3）网页分析器
4）爬虫调用器
5）价值数据使用

爬虫实现

1）调度器实现

# coding:utf-8
import url_manager
import html_downloader
import html_parser
import html_outputer
import url_manager
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, root_url):
        count = 1
        self.urls.add_new_url(root_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 == 1000:
                    break
                count = 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)

2）URL管理器实现

class UrlManager(object):
    def __init__(self):
        self.new_urls = set()
        self.old_urls = set()

    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)

    def add_new_urls(self, urls):
        if urls is None or len(urls) == 0:
            return
        for url in urls:
            self.add_new_url(url)

    def has_new_url(self):
        return len(self.new_urls) != 0

    def get_new_url(self):
        new_url = self.new_urls.pop()
        self.old_urls.add(new_url)
        return new_url

3）URL下载器实现

import urllib2
class HtmlDownloader(object):
    def download(self, url):
        if url is None:
            return None
        response = urllib2.urlopen(url)
        if response.getcode() != 200:
            return None
        return response.read()

4）URL解析器实现

from bs4 import BeautifulSoup
import re
import urlparse
class HtmlParser(object):
    def _get_new_urls(self, page_url, soup):
        new_urls = set()
        links = soup.find_all(&#39;a&#39;, href=re.compile(r"/view/\d+\.htm"))
        for link in links:
            new_url = link[&#39;href&#39;]
            new_full_url = urlparse.urljoin(page_url, new_url)
            new_urls.add(new_full_url)
        return new_urls

    def _get_new_data(self, page_url, soup):
        res_data = {}
        res_data[&#39;url&#39;] = page_url
        title_node = soup.find(&#39;dd&#39;, class_="lemmaWgt-lemmaTitle-title").find("h1")
        res_data[&#39;title&#39;] = title_node.get_text()
        summary_node = soup.find(&#39;div&#39;, class_="lemma-summary")
        res_data[&#39;summary&#39;] = summary_node.get_text()
        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, &#39;html.parser&#39;, from_encoding=&#39;utf-8&#39;)
        new_urls = self._get_new_urls(page_url, soup)
        new_data = self._get_new_data(page_url, soup)
        return new_urls, new_data

5）价值数据输出显示

# coding:utf-8
class HtmlOutputer(object):
    def __init__(self):
        self.datas = []

    def collect_data(self, data):
        if data is None:
            return
        self.datas.append(data)

    def output_html(self):
        fout = open(&#39;output.html&#39;, &#39;w&#39;)
        fout.write("<html>")
        fout.write("<meta charset=\"UTF-8\">")
        fout.write("<body>")
        fout.write("<table>")
        for data in self.datas:
            fout.write("<tr>")
            fout.write("<td>%s</td>" % data[&#39;url&#39;])
            fout.write("<td>%s</td>" % data[&#39;title&#39;].encode(&#39;utf-8&#39;))
            fout.write("<td>%s</td>" % data[&#39;summary&#39;].encode(&#39;utf-8&#39;))
            fout.write("</tr>")
        fout.write("</table>")
        fout.write("</body>")
        fout.write("</html>")
        fout.close()

执行

本爬虫为爬取百度百科与Python关键字相关的1000个静态网页，对网页中的数据，主要提取关键词和摘要信息，并将爬取的信息以HTML文件的方式存储，之后利用浏览器打开即可实现访问。

Déclaration：

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