最近一直在学习python，学习完了基本语法就练习了一个爬虫demo，下面总结下。
主要逻辑是
1）初始化url管理器，也就是将rooturl加入到url管理器中
2）在url管理器中得到新的new_url
3）根据新new_url得到它的内容html_cont (工具 urllib.request.urlopen(url))
4）解析这个新页面的内容html_cont并得到新的子url，并保存解析内容结果 （利用BeautifulSoup工具）
5）将新得到的子url保存到url管理器
6）迭代2-5步骤，知道输出某个阈值的数量即可停止
7）输出爬去的结果
注意编码问题，一致为UTF-8 -- .decode('UTF-8')
BeautifulSoup工具的安装方式：进入Python3.xScript下 输入指令 pip install beautifulsoup4
主页面spider_main.py:
''' Created on 2016-3-30 @author: rongyu ''' from bike_spider 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, 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 == 100: break count = count + 1 except: print('craw failed') self.outputer.output_html() #主程序入口 if __name__=="__main__": root_url = "http://baike.baidu.com/view/21087.htm" obj_spider = SpiderMain() obj_spider.craw(root_url) #根据url开始爬取
url管理器页面UrlManager.py
''' Created on 2016-3-30 @author: rongyu ''' 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 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 def add_new_urls(self,urls): if urls is None or len(urls) == 0: return for url in urls: self.add_new_url(url)
下载器页面 HtmlDownloader.py
import urllib.request class HtmlDownloader(object): def download(self,url): if url is None: return None response = urllib.request.urlopen(url) return response.read().decode('UTF-8')
解析器页面HtmlParser.py
from bs4 import BeautifulSoup import re import urllib.parse class HtmlParser(object): def _get_new_urls(self, page_url, soup): new_urls = set() #/view/234.htm links = soup.find_all('a',href=re.compile(r"/view/d+.htm")) for link in links: new_url = link['href'] new_full_url = urllib.parse.urljoin(page_url,new_url) new_urls.add(new_full_url) return new_urls def _get_new_data(self, page_url, soup): res_data = {} #url res_data['url'] = page_url #<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() #<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 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
输出器的代码HtmlOutputer.py
class HtmlOutputer(object): def __init__(self): self.datas = [] def collect_data(self,data): if data is None: #print("collect_data -data is none!") return self.datas.append(data) #print(self.datas) def output_html(self): fout = open('output.html','w') fout.write("<html>") 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>")
实验结果：
控制台输出
