• python爬取豆瓣电影首页超链接


    什么是爬虫? 

    我们可以把互联网比作一张大网,而爬虫(即网络爬虫)便是在网上爬行的蜘蛛。把网的节点比作一个个网页,爬虫爬到这就相当于访问了该页面,获取了其信息。可以把节点间的连线比作网页与网页之间的链接关系,这样蜘蛛通过一个节点后,可以顺着节点连线继续爬行到达下一个节点,即通过一个网页继续获取后续的网页,这样整个网的节点便可以被蜘蛛全部爬行到,网站的数据就可以被抓取下来了

    代码: 

      1 from urllib import request
      2 from collections import deque
      3 from pybloom_live import BloomFilter
      4 from lxml import etree
      5 import hashlib
      6  
      7 class crawel_bfs:  
      8     request_header={
      9             'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8',
     10             'Accept-Encoding': 'br',
     11             'Accept-Language': 'zh-CN,zh;q=0.9',
     12             'Cache-Control': 'max-age=0',
     13             'Connection': 'keep-alive',
     14             'Cookie': 'bid=Kn9AT5duD7k; gr_user_id=32e433a7-19f0-4e17-80c4-56b58d7c0056; _vwo_uuid_v2=5985FEE132C29EC9C840D6C5EDD95323|67c2ccc8467fc02a9cce6928e86ea013; ll="118281"; __yadk_uid=I4Ki5RUaEWOUdpVIjJfRYo1MEuaW36hA; __utmv=30149280.16369; viewed="10483489_1115600_2230208_26857712_1569487_1623164_26708119_26677686"; __utma=30149280.965685249.1516632348.1528892392.1530880979.81; __utmc=30149280; __utmz=30149280.1530880979.81.57.utmcsr=baidu|utmccn=(organic)|utmcmd=organic; __utmt=1; __utmb=30149280.1.10.1530880979; _pk_ref.100001.4cf6=%5B%22%22%2C%22%22%2C1530880982%2C%22https%3A%2F%2Fwww.douban.com%2F%22%5D; _pk_ses.100001.4cf6=*; __utma=223695111.2038558801.1520348154.1528892435.1530880982.55; __utmb=223695111.0.10.1530880982; __utmc=223695111; __utmz=223695111.1530880982.55.51.utmcsr=douban.com|utmccn=(referral)|utmcmd=referral|utmcct=/; _pk_id.100001.4cf6=da4243a2a9e242f1.1520348154.54.1530881042.1528892472.',
     15             'Host': 'movie.douban.com',
     16             'Referer': 'https://www.douban.com/',
     17             'Upgrade-Insecure-Requests': '1',
     18             'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'
     19             }
     20     
     21     cur_level=0
     22     max_level=2
     23         
     24     download_bf=BloomFilter(1024*1024,0.01)
     25     
     26     childque=deque()
     27     nowque=deque()
     28     
     29     def __init__(self,url,file_md5name,file_urlname):
     30         self.file_urlNameMd5_name=file_md5name
     31         self.file_urlName_name=file_urlname
     32         self.deal_file_md5=open(self.file_urlNameMd5_name,'r')
     33         self.file_md5=self.deal_file_md5.readlines()
     34         #用于输入现有的文件
     35         for url_md5_name in self.file_md5:
     36             #-1表示的是换行符,读入时换行符不会占据两个字符
     37             self.download_bf.add(url_md5_name[:-1])
     38         self.deal_file_md5.close()
     39         self.file_md5=open(self.file_urlNameMd5_name,'a')     
     40         self.file_url=open(self.file_urlName_name,'a')
     41         self.nowque.append(url)
     42     
     43     def indeque(self,url):
     44         self.nowque.append(url)
     45         
     46     def outdeque(self):
     47         try:
     48             url=self.nowque.popleft()
     49             return url
     50         except Exception:
     51             self.cur_level+=1
     52             if self.cur_level==self.max_level:
     53                 return None
     54             if len(self.childque)==0:
     55                 return None
     56             self.nowque=self.childque
     57             self.childque=deque()
     58             return self.nowque.popleft()
     59         
     60     def crawler(self,url):
     61           try:
     62             #创建一个request对象,封装一个报文对象
     63             req=request.Request(url,headers=self.request_header)
     64             #发送报文
     65             response=request.urlopen(req)
     66             html_page=response.read()
     67             #按照固定编码解码
     68             html=etree.HTML(html_page.lower().decode('utf-8'))
     69             url_list=html.xpath('//a/@href')
     70             for url in url_list:
     71                 if url.find('javascript:')!=-1:
     72                     continue
     73                 if url.startswith('http://') is False:
     74                     if url.startswith('/') is True:
     75                         url='http://movie.douban.com'+url
     76                     else:
     77                         continue
     78                 if url[-1]=='/':
     79                     url=url[:-1]
     80                 temp=hashlib.md5(url.encode('utf-8')).hexdigest()
     81                 if temp not in self.download_bf:
     82                     self.download_bf.add(url)
     83                     self.childque.append(url)
     84                     self.file_md5.write(temp+'\n')
     85                     self.file_url.write(url+'\n')
     86           except Exception:
     87             print("出现异常")
     88         
     89     def startcrawler(self):
     90         while True:
     91             url=self.outdeque()
     92             if url!=None:
     93                 print("现在爬取"+url+"的超链接")
     94                 self.crawler(url)
     95             else:
     96                 break
     97         self.file_md5.close()
     98         self.file_url.close()
     99         
    100 crawel=crawel_bfs("https://movie.douban.com/",'urlmd5.txt',
    101                   'urlname.txt')
    102 crawel.startcrawler()

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  • 原文地址:https://www.cnblogs.com/huanghuangwei/p/11736165.html
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