Python学习之网页抓取（二）

最新推荐文章于 2025-08-19 19:20:53 发布

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#Python列表字典 #正则表达式

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本文详细介绍了如何使用Python实现对下载网页内容的进一步提取，包括网页编码类型、标题等信息。通过正则表达式匹配，实现对网页元数据的解析，并提供了一个用于遍历和下载URL链接的模块。

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这一篇实现的功能是：对下载的网页内容进一步提取内容，如网页编码类型，标题等。

#!/usr/bin/env python
# -*- coding: GBK -*-
'''
Created on Jul 17, 2013
@author: belong
'''

import urllib
import re

class Tools:
    def write_log(self, level, info):
        print '[' + level + ']' + info
    def match_regex(self,pattern,src):
        result = ""
        com = re.compile(pattern,re.I)
        matchers = com.findall(src)
        print matchers
        for matcher in matchers:
            result += matcher +" "
        return result.strip()#strip函数返回去掉两端空格的字符串
           
class Crawler:
    #获取一个url链接的所有urls
    def get_url(self, url):
        html = urllib.urlopen(url)
    #     pattern = re.compile("http://.*?\.com",re.I)
        pattern = re.compile(r'[a-zA-z]+://[^\s]*\.html?', re.I)
        while True:
            data = html.read()
            if data:
                urls = pattern.findall(data)
            else:
                break
        html.close()
        return urls
    
    #下载url对应网页
    def download_url(self, url, filename):
        Tools().write_log("info","开始下载")
        html = urllib.urlopen(url)
        f = open(filename, 'w')
        while True:
            page = html.read()
            if page:
                f.write(page);
            else:
                break
        html.close()
        f.close()
        Tools().write_log("info","网页下载成功")
        return page
    
    #广度优先遍历
    def broad_traverse(self, start_url, number):
        Tools().write_log("info","开始遍历")
        visited = []
        unvisited = []
        unvisited.append(start_url)
        while len(unvisited):
            if len(visited) < number:
                url = unvisited.pop(0);
                print url, len(visited)
                i = len(visited)
#                 self.download_url(url, str(i) + '.html')
                visited.append(url)
                url_list = self.get_url(url)
                for eachlink in url_list:
                    if ((unvisited.count(eachlink) == 0) & (visited.count(eachlink) == 0)):
                        unvisited.append(eachlink)
            else:
                break
        Tools().write_log("info","遍历成功")
        return visited 
    
    def main(self):
        start_url = "http://www.baidu.com"
        self.broad_traverse(start_url, 10)

#数据提取类
class DataExtractor:
    #提取标题
    def get_title(self,data):
        title = Tools().match_regex('<title>.*?<\/title>', data)
        if title == "":
            Tools().write_log( "Error", "标题匹配不成功")
        return title
    #提取内容格式
    def get_type(self,data):
        type = Tools().match_regex('<meta.*content=.*?\/>', data)
        return type
    #提取字符类型
    def get_charset(self,data):
        charset = Tools().match_regex('<meta.*?charset=.*?\/>', data)
        return charset
    
    def get_info(self,url):
        try:
            data = Crawler().download_url(url,str(11)+'.html')
        except:
            Tools().write_log("error", url+"抓取失败")
            raise
    
        Tools().write_log("info", "开始数据匹配")
        rst = {}#rst是一个字典
        rst['title'] = self.get_title(data)
        print "title:",rst['title'] 
        rst['type'] = self.get_type(data)
        print "type:",rst['type'] 
        rst['charset'] = self.get_charset(data)
        print "charset:",rst['charset'] 
        Tools().write_log("DEBUG",'title=%s,type=%s,type=%s'%(rst['title'],rst['type'],rst['charset']))
        return rst

def main():
    start_url = "http://www.baidu.com"
    crawler = Crawler()
    url_list = crawler.broad_traverse(start_url, 10)   
    dataExtractor= DataExtractor()
    for url in url_list:
        dataExtractor.get_info(url)

main()