python-爬虫(3)---lxml匹配css

百度首页  部分代码

<div class="s_tab_inner">
　　<b>网页</b>
　　<a href="//www.baidu.com/s?rtt=1&bsst=1&cl=2&tn=news&word=" wdfield="word" onmousedown="return c({'fm':'tab','tab':'news'})" sync="true">资讯</a>
　　<a href="http://tieba.baidu.com/f?kw=&fr=wwwt" wdfield="kw" onmousedown="return c({'fm':'tab','tab':'tieba'})">贴吧</a>
　　<a href="http://zhidao.baidu.com/q?ct=17&pn=0&tn=ikaslist&rn=10&word=&fr=wwwt" wdfield="word" onmousedown="return c({'fm':'tab','tab':'zhidao'})">知道</a>
　　<a href="http://music.taihe.com/search?fr=ps&ie=utf-8&key=" wdfield="key" onmousedown="return c({'fm':'tab','tab':'music'})">音乐</a>
　　<a href="http://image.baidu.com/search/index?tn=baiduimage&ps=1&ct=201326592&lm=-1&cl=2&nc=1&ie=utf-8&word=" wdfield="word" onmousedown="return c({'fm':'tab','tab':'pic'})">图片</a>
　　<a href="http://v.baidu.com/v?ct=301989888&rn=20&pn=0&db=0&s=25&ie=utf-8&word=" wdfield="word" onmousedown="return c({'fm':'tab','tab':'video'})">视频</a>
　　<a href="http://map.baidu.com/m?word=&fr=ps01000" wdfield="word" onmousedown="return c({'fm':'tab','tab':'map'})">地图</a>
　　<a href="http://wenku.baidu.com/search?word=&lm=0&od=0&ie=utf-8" wdfield="word" onmousedown="return c({'fm':'tab','tab':'wenku'})">文库</a>
　　<a href="//www.baidu.com/more/" onmousedown="return c({'fm':'tab','tab':'more'})">更多»</a>
</div>

根据css查找符合条件的内容