Python网络爬虫之基本项目：爬取网易新闻排行榜

1. 最基本的抓取

抓取大多数情况属于get请求，即直接从对方服务器上获取数据。

首先，Python中自带urllib及urllib2这两个模块，基本上能满足一般的页面抓取。另外，requests也是非常有用的包，与此类似的，还有httplib2等等。

Requests：
	import requests
	response = requests.get(url)
	content = requests.get(url).content
	print "response headers:", response.headers
	print "content:", content
Urllib2：
	import urllib2
	response = urllib2.urlopen(url)
	content = urllib2.urlopen(url).read()
	print "response headers:", response.headers
	print "content:", content
Httplib2：
	import httplib2
	http = httplib2.Http()
	response_headers, content = http.request(url, 'GET')
	print "response headers:", response_headers
	print "content:", content

此外，对于带有查询字段的url，get请求一般会将来请求的数据附在url之后，以?分割url和传输数据，多个参数用&连接。

data = {'data1':'XXXXX', 'data2':'XXXXX'}
Requests：data为dict，json
	import requests
	response = requests.get(url=url, params=data)
Urllib2：data为string
	import urllib, urllib2    
	data = urllib.urlencode(data)
	full_url = url+'?'+data
	response = urllib2.urlopen(full_url)

 

抓取网易新闻排行榜项目一些说明：

• 使用urllib2或requests包来爬取页面。

• 使用正则表达式分析一级页面，使用Xpath来分析二级页面。

• 将得到的标题和链接，保存为本地文件。

代码分享：

# -*- coding: utf-8 -*-
import os
import sys
import urllib2
import requests
import re
from lxml import etree


def StringListSave(save_path, filename, slist):
    if not os.path.exists(save_path):
        os.makedirs(save_path)
    path = save_path+"/"+filename+".txt"
    with open(path, "w+") as fp:
        for s in slist:
            fp.write("%s\t\t%s\n" % (s[0].encode("utf8"), s[1].encode("utf8")))

def Page_Info(myPage):
    '''Regex'''
    mypage_Info = re.findall(r'<div class="titleBar" id=".*?"><h2>(.*?)</h2><div class="more"><a href="(.*?)">.*?</a></div></div>', myPage, re.S)
    return mypage_Info

def New_Page_Info(new_page):
    '''Regex(slowly) or Xpath(fast)'''
    # new_page_Info = re.findall(r'<td class=".*?">.*?<a href="(.*?)\.html".*?>(.*?)</a></td>', new_page, re.S)
    # # new_page_Info = re.findall(r'<td class=".*?">.*?<a href="(.*?)">(.*?)</a></td>', new_page, re.S) # bugs
    # results = []
    # for url, item in new_page_Info:
    #     results.append((item, url+".html"))
    # return results
    dom = etree.HTML(new_page)
    new_items = dom.xpath('//tr/td/a/text()')
    new_urls = dom.xpath('//tr/td/a/@href')
    assert(len(new_items) == len(new_urls))
    return zip(new_items, new_urls)

def Spider(url):
    i = 0
    print "downloading ", url
    myPage = requests.get(url).content.decode("gbk")
    # myPage = urllib2.urlopen(url).read().decode("gbk")
    myPageResults = Page_Info(myPage)
    save_path = u"网易新闻抓取"
    filename = str(i)+"_"+u"新闻排行榜"
    StringListSave(save_path, filename, myPageResults)
    i += 1
    for item, url in myPageResults:
        print "downloading ", url
        new_page = requests.get(url).content.decode("gbk")
        # new_page = urllib2.urlopen(url).read().decode("gbk")
        newPageResults = New_Page_Info(new_page)
        filename = str(i)+"_"+item
        StringListSave(save_path, filename, newPageResults)
        i += 1


if __name__ == '__main__':
    print "start"
    start_url = "http://news.163.com/rank/"
    Spider(start_url)
    print "end"

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