CSS/Xpath 选择器第几个子节点/父节点/兄弟节点

Posted 2020-11-02 my8100

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了CSS/Xpath 选择器第几个子节点/父节点/兄弟节点相关的知识，希望对你有一定的参考价值。

0.参考

1.初始化

In [325]: from scrapy import Selector

In [326]: text="""
     ...: <div>
     ...:     <a>1a</a>
     ...:     <p>2p</p>
     ...:     <p>3p</p>
     ...: </div>"""

In [327]: sel=Selector(text=text)

In [328]: print(sel.extract())
<html><body><div>
    <a>1a</a>
    <p>2p</p>
    <p>3p</p>
</div></body></html>

2.父节点/上一个下一个兄弟节点

In [329]: sel.xpath(‘//a/parent::*/p‘).extract()
Out[329]: [‘<p>2p</p>‘, ‘<p>3p</p>‘]

In [330]: sel.xpath(‘//p/preceding-sibling::a‘).extract()
Out[330]: [‘<a>1a</a>‘]

In [331]: sel.xpath(‘//a/following-sibling::p‘).extract()
Out[331]: [‘<p>2p</p>‘, ‘<p>3p</p>‘]

3.CSS 第几个子节点

3.1 通用

#完整子节点列表，从第一个子节点开始计数，并且满足子节点tag限定
In [332]: sel.css(‘a:nth-child(1)‘).extract()
Out[332]: [‘<a>1a</a>‘]
#完整子节点列表，从最后一个子节点开始计数，并且满足子节点tag限定
In [333]: sel.css(‘a:nth-last-child(1)‘).extract()
Out[333]: []


In [334]: sel.css(‘p:nth-child(1)‘).extract()
Out[334]: []

In [335]: sel.css(‘p:nth-child(2)‘).extract()
Out[335]: [‘<p>2p</p>‘]

In [336]: sel.css(‘p:nth-child(3)‘).extract()
Out[336]: [‘<p>3p</p>‘]

In [337]: sel.css(‘p:nth-last-child(1)‘).extract()
Out[337]: [‘<p>3p</p>‘]

In [338]: sel.css(‘p:nth-last-child(2)‘).extract()
Out[338]: [‘<p>2p</p>‘]

In [339]: sel.css(‘p:nth-last-child(3)‘).extract()
Out[339]: []

3.2 特别指代

In [340]: sel.css(‘a:first-child‘).extract()
Out[340]: [‘<a>1a</a>‘]

In [341]: sel.css(‘a:last-child‘).extract()
Out[341]: []

In [342]: sel.css(‘p:first-child‘).extract()
Out[342]: []

In [343]: sel.css(‘p:last-child‘).extract()
Out[343]: [‘<p>3p</p>‘]

3.3 上述 -child 修改为 -of-type ，仅对过滤后的相应子节点列表进行计数

4.Xpath 第几个子节点

In [344]: sel.xpath(‘//div‘).extract()
Out[344]: [‘<div>\n    <a>1a</a>\n    <p>2p</p>\n    <p>3p</p>\n</div>‘]

In [345]: sel.xpath(‘//div/*‘).extract()
Out[345]: [‘<a>1a</a>‘, ‘<p>2p</p>‘, ‘<p>3p</p>‘]

In [346]: sel.xpath(‘//div/node()‘).extract()
Out[346]: [‘\n    ‘, ‘<a>1a</a>‘, ‘\n    ‘, ‘<p>2p</p>‘, ‘\n    ‘, ‘<p>3p</p>‘, ‘\n‘]

In [347]: sel.xpath(‘//div/a‘).extract()
Out[347]: [‘<a>1a</a>‘]

In [348]: sel.xpath(‘//div/p‘).extract()
Out[348]: [‘<p>2p</p>‘, ‘<p>3p</p>‘]

In [349]:

In [349]: sel.xpath(‘//div/a[1]‘).extract()
Out[349]: [‘<a>1a</a>‘]

In [350]: sel.xpath(‘//div/a[last()]‘).extract()
Out[350]: [‘<a>1a</a>‘]

In [351]:

In [351]: sel.xpath(‘//div/p[1]‘).extract()    #相当于过滤后的子节点列表
Out[351]: [‘<p>2p</p>‘]

In [352]: sel.xpath(‘//div/p[last()]‘).extract()
Out[352]: [‘<p>3p</p>‘]

In [353]: sel.xpath(‘//div/p[last()-1]‘).extract()
Out[353]: [‘<p>2p</p>‘]

In [354]:

In [354]: sel.xpath(‘//div/*[1]‘).extract()        #完整子节点列表
Out[354]: [‘<a>1a</a>‘]

In [355]: sel.xpath(‘//div/*[last()]‘).extract()
Out[355]: [‘<p>3p</p>‘]

In [356]:

In [356]: sel.xpath(‘//div/node()[1]‘).extract()   #包括纯文本    
Out[356]: [‘\n    ‘]

In [357]: sel.xpath(‘//div/node()[last()]‘).extract()
Out[357]: [‘\n‘]