Python爬虫，爬取百度百科词条爬虫

看了慕课网的一个网络爬虫教程。模仿着写了一个简单的爬取百度百科的例子。
（1）安装Beautifulsoup4

Beautifulsoup是Python的一个网页解析库，使用起来很方便。http://cuiqingcai.com/1319.html这个链接是介绍如何使用。这个库是需要安装的，进入Pthon安装目录下面的Scripts目录，执行pip install beautifulsoup进行安装。

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（2）爬虫具体实现
爬虫分为5个模块，调度模块、网页下载模块、网页解析模块、URL管理模块、输出模块。

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【Python爬虫，爬取百度百科词条】URL管理模块，负责保存最新的网页URL，每次取出最新的URL进行爬取。

#coding=utf8 class UrlManager(object):def __init__(self): self.new_urls = set() self.old_urls = set()#添加新的url 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)#批量添加url def add_new_urls(self,urls): if urls is None or len(urls) == 0: returnfor url in urls: self._add_new_url(url)#是否有新的url def has_new_url(self): return len(self.new_urls) != 0#获取新的url def get_new_url(self): new_url = self.new_urls.pop() self.old_urls.add(new_url)return new_url

URL下载模块，负责把网页的内容下载下来，使用urllib2库进行下载。

#coding utf8import urllib2class HtmlDownloader(object):def download(self, url): if url is None: return Noneresponse = urllib2.urlopen(url); if response.getcode == 200: return Nonereturn response.read()

URL解析模块，使用Beautifulsoup把当前网页的其他链接和网页简介解析出来。

# coding:utf-8 import urlparsefrom bs4 import BeautifulSoup import reclass HtmlParser(object): def parser(self, page_url, html_content): if page_url is None or html_content is None: return soup = BeautifulSoup(html_content, "html.parser", from_encoding="utf-8") new_urls = self._get_new_urls(page_url, soup) new_data = https://www.it610.com/article/self._get_new_data(page_url, soup)return new_urls, new_datadef _get_new_urls(self, page_url, soup): new_urls = set()links = soup.find_all('a', href=https://www.it610.com/article/re.compile(r'/item/'))for link in links: new_url = link["href"] new_url_full = urlparse.urljoin(page_url, new_url) new_urls.add(new_url_full)return new_urlsdef _get_new_data(self, page_url, soup): res_data = https://www.it610.com/article/{}res_data['url'] = page_url#
Python title_node = soup.find('dd', class_="lemmaWgt-lemmaTitle-title").find('h1') res_data['title'] = title_node.get_text()# summary_node = soup.find("div", class_="lemma-summary") res_data['summary'] = summary_node.get_text()return res_data

输出模块，负责把解析的网页内容保存起来。

#coding=utf-8class HtmlOutputer(object):def __init__(self): self.datas = []def collect_data(self,data): if data is None: returnself.datas.append(data)def outpute_html(self): fout = open("outputer.html",'w') fout.write("") fout.write("") fout.write("")for data in self.datas: fout.write("") fout.write("")fout.write("") fout.write("") fout.write("%s " % data['url']) fout.write(" %s " % data['title'].encode('utf-8')) fout.write(" %s " % data['summary'].encode('utf-8')) fout.write("")

最后是调度模块，把各个模块之间的功能调度起来

#coding:utf8 import url_manager import html_downloader import html_outputer import 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() passdef craw(self, root_url): self.urls._add_new_url(root_url)count = 1; while self.urls.has_new_url():try: new_url = self.urls.get_new_url() print new_url#得到url的内容 html_content = self.downloader.download(new_url)#得到url的内容和url new_urls,new_data = https://www.it610.com/article/self.parser.parser(new_url,html_content)self.urls.add_new_urls(new_urls)self.outputer.collect_data(new_data) except: print"splider failed"if (count == 10): breakcount = count + 1; self.outputer.outpute_html()if __name__ == "__main__": root_url = "https://baike.baidu.com/item/Python/407313"obj_splider = SpiderMain() obj_splider.craw(root_url)

工程目录如下：