Get second element text with XPath?

问题

<span class='python'>
  <a>google</a>
  <a>chrome</a>
</span>

I want to get chrome and have it working like this already.

q = item.findall('.//span[@class="python"]//a')
t = q[1].text # first element = 0

I'd like to combine it into a single XPath expression and just get one item instead of a list.
I tried this but it doesn't work.

t = item.findtext('.//span[@class="python"]//a[2]') # first element = 1

And the actual, not simplified, HTML is like this.

<span class='python'>
  <span>
    <span>
      <img></img>
      <a>google</a>
    </span>
    <a>chrome</a>
  </span>
</span>

回答1:

I tried this but it doesn't work.
t = item.findtext('.//span[@class="python"]//a[2]')

This is a FAQ about the // abbreviation.

.//a[2] means: Select all a descendents of the current node that are the second a child of their parent. So this may select more than one element or no element -- depending on the concrete XML document.

To put it more simply, the [] operator has higher precedence than //.

If you want just one (the second) of all nodes returned you have to use brackets to force your wanted precedence:

(.//a)[2]

This really selects the second a descendent of the current node.

For the actual expression used in the question, change it to:

(.//span[@class="python"]//a)[2]

or change it to:

(.//span[@class="python"]//a)[2]/text()

回答2:

I'm not sure what the problem is...

>>> d = """<span class='python'>
...   <a>google</a>
...   <a>chrome</a>
... </span>"""
>>> from lxml import etree
>>> d = etree.HTML(d)
>>> d.xpath('.//span[@class="python"]/a[2]/text()')
['chrome']
>>>

回答3:

From Comments:

or the simplification of the actual HTML I posted is too simple

You are right. What is the meaning of .//span[@class="python"]//a[2]? This will be expanded to:

self::node()
 /descendant-or-self::node()
  /child::span[attribute::class="python"]
   /descendant-or-self::node()
    /child::a[position()=2]

It will finaly select the second a child (fn:position() refers to the child axe). So, nothing will be select if your document is like:

<span class='python'> 
  <span> 
    <span> 
      <img></img> 
      <a>google</a><!-- This is the first "a" child of its parent --> 
    </span> 
    <a>chrome</a><!-- This is also the first "a" child of its parent --> 
  </span> 
</span>

If you want the second of all descendants, use:

descendant::span[@class="python"]/descendant::a[2]

来源：https://stackoverflow.com/questions/4117953/get-second-element-text-with-xpath

标签

python

xpath

lxml