Python 使用 XPath 获取第二个元素文本？
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Get second element text with XPath?
提问by
<span class='python'>
<a>google</a>
<a>chrome</a>
</span>
I want to get chromeand have it working like this already.
我想得到chrome并让它像这样工作。
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.
我想将它组合成一个 XPath 表达式，只得到一个项目而不是一个列表。
我试过这个，但它不起作用。
t = item.findtext('.//span[@class="python"]//a[2]') # first element = 1
And the actual, not simplified, HTML is like this.
而实际的，而不是简化的 HTML 是这样的。
<span class='python'>
<span>
<span>
<img></img>
<a>google</a>
</span>
<a>chrome</a>
</span>
</span>
采纳答案by Dimitre Novatchev
I tried this but it doesn't work.
t = item.findtext('.//span[@class="python"]//a[2]')
我试过这个，但它不起作用。
t = item.findtext('.//span[@class="python"]//a[2]')
This is a FAQ about the //abbreviation.
这是关于//缩写的常见问题解答。
.//a[2]means: Select all adescendents of the current node that are the second achild of their parent. So this may select more than one element or no element -- depending on the concrete XML document.
.//a[2]意思是：选择a当前节点的所有后代a，它们是其父节点的第二个子节点。因此，这可能会选择多个元素或不选择元素——这取决于具体的 XML 文档。
To put it more simply, the []operator has higher precedence than //.
更简单地说，[]运算符的优先级高于//。
If you want just one (the second) of all nodes returned you have to use brackets to force your wanted precedence:
如果您只想返回所有节点中的一个（第二个），则必须使用括号来强制您想要的优先级：
(.//a)[2]
(.//a)[2]
This really selects the second adescendent of the current node.
这实际上选择a了当前节点的第二个后代。
For the actual expression used in the question, change it to:
对于问题中使用的实际表达式，将其更改为：
(.//span[@class="python"]//a)[2]
or change it to:
或将其更改为：
(.//span[@class="python"]//a)[2]/text()
回答by MattH
I'm not sure what the problem is...
我不确定是什么问题...
>>> 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by MattH
From Comments:
来自评论：
or the simplification of the actual HTML I posted is too simple
或者我贴的实际HTML的简化太简单了
You are right. What is the meaning of .//span[@class="python"]//a[2]? This will be expanded to:
你是对的。是什么意思.//span[@class="python"]//a[2]？这将扩展为：
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 achild (fn:position()refers to the childaxe). So, nothing will be select if your document is like:
它将最终选择第二个a孩子（fn:position()指的是child斧头）。因此，如果您的文档如下所示，则不会选择任何内容：
<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:
如果您想要所有后代中的第二个，请使用：
descendant::span[@class="python"]/descendant::a[2]
