1、spider_main.py

#coding:utf8
import url_manager,html_downloader,html_outputer,html_parser

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_content = self.downloader.download(new_url)
                new_urls,new_data = self.parser.parse(new_url,html_content)
                self.urls.add_new_urls(new_urls)
                self.outputer.collect_data(new_data)
                if count == 100:
                    break
                count = count + 1
            except Exception as e:
                        print str(e)
                        print "craw failed"

        self.outputer.output_html()

if __name__=="__main__":
    root_url = "http://baike.baidu.com/item/Python"
    obj_spider = SpiderMain()
    obj_spider.craw(root_url)

2、html_downloader.py

import urllib2

class HtmlDownloader(object):
    def download(self,url):
        if url is None:
            return

        response = urllib2.urlopen(url)
        if response.getcode() != 200:
            return None        
        return response.read()

3、html_parser.py

#encoding:utf8
from bs4 import  BeautifulSoup
import re
import urlparse

class HtmlParser(object):
    def parse(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 = self._get_new_data(page_url,soup)

        return new_urls,new_data

    def _get_new_urls(self,page_url,soup):
        new_urls = set()
        links = soup.find_all('a',href=re.compile(r"/item/.+"))
        for link in links:
            new_url = link['href']
           # new_full_url = urlparse.urljoin(page_url,new_url)
            new_full_url = r"http://baike.baidu.com%s"%new_url
            new_urls.add(new_full_url)
        return new_urls

    def _get_new_data(self,page_url,soup):
        #res_data = set() 
        res_data = {}           
        res_data["url"] =  page_url

        #标题  
 
Python
        title_node = soup.find('dd',class_="lemmaWgt-lemmaTitle-title").find("h1")
        res_data["title"] = title_node.get_text()

        #简介        
        summary_node = soup.find('div',class_="lemma-summary")
        res_data["summary"] = summary_node.get_text()   

        return res_data

4、url_manager.py

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 None
        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.new_urls.add(url)

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

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

5、html_outputer.py

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("output.html","w")
        fout.write("")
        fout.write("")
        fout.write("")
        for data in self.datas:
            fout.write("")
            fout.write(r""%data["url"])
            fout.write(""%data["title"].encode("utf-8"))
            fout.write(""%data["summary"].encode("utf-8"))
            fout.write("")

        fout.write("
%s
%s
%s
")
        fout.write("")
        fout.write("")