python爬虫案例：使用XPath爬网页图片

用XPath来做一个简单的爬虫，尝试爬取某个贴吧里的所有帖子，并且将该这个帖子里每个楼层发布的图片下载到本地。

# -*- coding:utf-8 -*-

import urllib

import urllib2

from lxml import etree

def loadPage(url):

    """

        作用：根据url发送请求，获取服务器响应文件

        url: 需要爬取的url地址

    """

    #print url

    #headers = {"User-Agent" : "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_0) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11"}

    request = urllib2.Request(url)

    html = urllib2.urlopen(request).read()

    # 解析HTML文档为HTML DOM模型

    content = etree.HTML(html)

    #print content

    # 返回所有匹配成功的列表集合

    link_list = content.xpath('//div[@class="t_con cleafix"]/div/div/div/a/@href')

    #link_list = content.xpath('//a[@class="j_th_tit"]/@href')

    for link in link_list:

        fulllink = "http://tieba.baidu.com" + link

        # 组合为每个帖子的链接

        #print link

        loadImage(fulllink)

# 取出每个帖子里的每个图片连接

def loadImage(link):

    headers = {"User-Agent" : "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36"}

    request = urllib2.Request(link, headers = headers)

    html = urllib2.urlopen(request).read()

    # 解析

    content = etree.HTML(html)

    # 取出帖子里每层层主发送的图片连接集合

    #link_list = content.xpath('//img[@class="BDE_Image"]/@src')

    # link_list = content.xpath('//div[@class="post_bubble_middle"]')

    link_list = content.xpath('//img[@class="BDE_Image"]/@src')

    # 取出每个图片的连接

    for link in link_list:

        # print link

        writeImage(link)

def writeImage(link):

    """

        作用：将html内容写入到本地

        link：图片连接

    """

    #print "正在保存 " + filename

    headers = {"User-Agent" : "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36"}

    # 文件写入

    request = urllib2.Request(link, headers = headers)

    # 图片原始数据

    image = urllib2.urlopen(request).read()

    # 取出连接后10位做为文件名

    filename = link[-10:]

    # 写入到本地磁盘文件内

    with open(filename, "wb") as f:

        f.write(image)

    print "已经成功下载 "+ filename

def tiebaSpider(url, beginPage, endPage):

    """

        作用：贴吧爬虫调度器，负责组合处理每个页面的url

        url : 贴吧url的前部分

        beginPage : 起始页

        endPage : 结束页

    """

    for page in range(beginPage, endPage + 1):

        pn = (page - 1) * 50

        #filename = "第" + str(page) + "页.html"

        fullurl = url + "&pn=" + str(pn)

        #print fullurl

        loadPage(fullurl)

        #print html

        print "谢谢使用"

if __name__ == "__main__":

    kw = raw_input("请输入需要爬取的贴吧名:")

    beginPage = int(raw_input("请输入起始页："))

    endPage = int(raw_input("请输入结束页："))

    url = "http://tieba.baidu.com/f?"

    key = urllib.urlencode({"kw": kw})

    fullurl = url + key

    tiebaSpider(fullurl, beginPage, endPage)

效果：