第七篇 css选择器实现字段解析

CSS选择器的作用实际和xpath的一样，都是为了定位具体的元素

举例我要爬取下面这个页面的标题

In []: title = response.css(".entry-header h1")

In []: title
Out[]: [<Selector xpath="descendant-or-self::*[@class and contains(concat(' ', normalize-space(@class), ' '), ' entry-header ')]/descendant-or-self::*/h1" data='<h1>谷歌用两年时间研究了 180 个团队，发现高效团队有这五个特征</h1>'>]

In []: title = response.css(".entry-header h1").extract()

In []: title
Out[]: ['<h1>谷歌用两年时间研究了 180 个团队，发现高效团队有这五个特征</h1>']

In []: ##可以使用css的::text取到内容

In []: title = response.css(".entry-header h1::text").extract()

In []: title
Out[]: ['谷歌用两年时间研究了 180 个团队，发现高效团队有这五个特征']

获取文章创建日期：

In []: date_text = response.css(".entry-meta-hide-on-mobile").extract()

In []: date_text
Out[]: ['<p class="entry-meta-hide-on-mobile">\r\n\r\n            2017/08/23 ·  <a href="http://blog.jobbole.com/category/career/" rel="category tag">职场</a>\r\n            \r\n                            · <a href="#article-comment"> 7 评论 </a>\r\n            \r\n\r\n            \r\n             ·  <a href="http://blog.jobbole.com/tag/google/">Google</a>, <a href="http://blog.jobbole.com/tag/%e5%9b%a2%e9%98%9f/">团队</a>\r\n            \r\n</p>']

In []: date_text = response.css(".entry-meta-hide-on-mobile::text").extract()

In []: date_text
Out[]:
['\r\n\r\n            2017/08/23 ·  ',
 '\r\n            \r\n                            · ',
 '\r\n            \r\n\r\n            \r\n             ·  ',
 ', ',
 '\r\n            \r\n']

In []: date_text = response.css(".entry-meta-hide-on-mobile::text").extract()[
    ...: ]

In []: date_text
Out[]: '\r\n\r\n            2017/08/23 ·  '

In []: date_text = response.css(".entry-meta-hide-on-mobile::text").extract()[
    ...: ].strip()

In []: date_text
Out[]: '2017/08/23 ·'

In []: date_text = response.css(".entry-meta-hide-on-mobile::text").extract()[
    ...: ].strip().replace("·","").strip()

In []: date_text
Out[]: '2017/08/23'

获取评论数

In []: comment_num = response.css("a[href='#article-comment']")

In []: comment_num
Out[]:
[<Selector xpath="descendant-or-self::a[@href = '#article-comment']" data='<a href="#article-comment"> 7 评论 </a>'>,
 <Selector xpath="descendant-or-self::a[@href = '#article-comment']" data='<a href="#article-comment"><span class="'>]

In []: comment_num = response.css("a[href='#article-comment'] span::text").ext
    ...: ract()

In []: comment_num
Out[]: [' 7 评论']

In []: comment_num = response.css("a[href='#article-comment'] span::text").ext
    ...: ract().strip()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input--18ae8761867f> in <module>()
---->  comment_num = response.css("a[href='#article-comment'] span::text").extract().strip()

AttributeError: 'list' object has no attribute 'strip'

In []: comment_num = response.css("a[href='#article-comment'] span::text").ext
    ...: ract()[]

In []: comment_num
Out[]: ' 7 评论'

In []: 

PS:css选择器里，不同标签使用空格隔开