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一个简单的Python爬虫

2016-04-09 12:25 531 查看

　　基于慕课网的教程实现了一个简单的爬虫，这个Python爬虫可以爬取百度百科上面与Python词条相关的词条的名子和摘要信息，并保存在名为output.html的文件里。

　　爬虫一共由五个部分组成，分别是spyder_main.py、html_downloader.py、html_outputer.py、html_parser.py和url_manager.py

　　spyder_main.py：主函数,主要用于实现模块间的调度

　　html_downloader.py：用来下载url

　　html_outputer.py：用来收集爬取的数据并输出成html

　　html_parser.py：用来解析url页面

　　url_manager.py：用于管理已经下载和还没有下载的url

　　具体代码如下：

spyder_main.py

import url_manager
import html_downloader
import html_outputer
import html_parser
class SpiderMain(object):
count = 1
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 ==10:
break

count = count + 1
except:
print 'craw failed'
self.outputer.output_html()

if __name__ == '__main__':
root_url = 'http://baike.baidu.com/link?url=iYGd6RePOS1xkyTpV0OoSrZ96YRjaPmaxxLgEH4yQFlepo11sn5g4E0oi6cu1hihq651LtUSr9ZVjIY4ePnPla'
//root_url是百度百科python页面的链接
obj_spider = SpiderMain()
obj_spider.craw(root_url)

html_downloader.py

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()

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)
return self.datas

def output_html(self):
fout = open('output.html','w')
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['url'])
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>')

html_parser.py

from bs4 import BeautifulSoup
import re
import urlparse

class HtmlParser(object):
def _get_new_urls(self,page_url,soup):
new_urls = set()
#/view/123.html
links = soup.find_all('a',href=re.compile(r"/view/\d+\.htm"))
for link in links:
new_url = link['href']
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['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

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
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

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