Python Xpath 仅选择具有匹配属性的直接兄弟
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Xpath to select only direct siblings with matching attributes
提问by Jens
I have the following example document:
我有以下示例文档：
<root>
<p class="b">A</p>
<p class="b">B</p>
<p class="a">C</p>
<p class="a">D</p>
<p class="b">E</p>
<x>
<p class="b">F</p>
</x>
</root>
I am looking for an xpath expression which selects all directsiblings of a given node with matching class attributes, not any sibling. In above example, the first two <p class="b">A-B should be selected; likewise the two <p class="a">C-D, likewise the fifth single <p class="b">E as it has no directsiblings; likewise the single <p class="b">F inside of <x>. Note that in this context B and C are not direct siblings because they have different class attribute valued!
我正在寻找一个 xpath 表达式，它选择具有匹配类属性的给定节点的所有直接兄弟节点，而不是任何兄弟节点。在上例中，<p class="b">应选择前两个AB；同样是两张<p class="a">CD，同样是第五张单曲<p class="b">E，因为它没有直接的兄弟姐妹；<p class="b">里面的单个F也是如此<x>。请注意，在此上下文中 B 和 C 不是直接兄弟姐妹，因为它们具有不同的类属性值！
What I have is this:
我有的是这个：
xml.xpath("//p") # This selects all six <p> elements.
xml.xpath("//p[@class='b']") # This selects all four <p class="b"> elements.
xml.xpath("//p/following-sibling::p[@class='b']") # This selects all <p class="b"> sibling elements, even though not direct siblings.
The last expression selects the fifth sibling as well, although there are non-matching siblings inbetween.
最后一个表达式也选择第五个兄弟姐妹，尽管中间有不匹配的兄弟姐妹。
How do I select only direct siblings with the same classvalue?
如何仅选择具有相同class值的直接兄弟姐妹？
EditTo clarify: note how the last two are individual selections, not siblings!
编辑澄清：注意最后两个是个人选择，而不是兄弟姐妹！
EditI have saved an example here. The Xpath expression based on /root/p[1]is supposed to select A, B, C, D.
编辑我在这里保存了一个例子。基于的 Xpath 表达式/root/p[1]应该选择A, B, C, D.
回答by Justin Ko
To get the very next sibling, you can add the position - 1 meaning right beside.
要获得下一个兄弟姐妹，您可以添加位置 - 1 表示就在旁边。
following-sibling::*[1]
To ensure that the next sibling is of a specific node type, you can add the following filter, where p is the node type we want to match.
为了确保下一个兄弟节点是特定的节点类型，您可以添加以下过滤器，其中 p 是我们要匹配的节点类型。
[self::p]
If you only want ones with the same attribute, you would also need to specify the attribute on the first p element.
如果您只想要具有相同属性的那些，您还需要在第一个 p 元素上指定该属性。
So if you just want class b p elements that are immediately after a class b p element, you can do the following. This would just give you the second p element.
因此，如果您只想要紧跟在 bp 类元素之后的 bp 类元素，则可以执行以下操作。这只会给你第二个 p 元素。
//p[@class='b']/following-sibling::*[1][@class='b'][self:p]
It sounds like you might actually want any class b element which is adjacent to another class b element. In that case, you can check the following and preceding sibling. The following would give you the first 2 p elements.
听起来您可能实际上想要任何与另一个 b 类元素相邻的 b 类元素。在这种情况下，您可以检查以下和前面的兄弟。以下将为您提供前 2 个 p 元素。
//p[@class='b'][following-sibling::*[1][@class='b'][self::p]
or preceding-sibling::*[1][@class='b'][self::p]]
回答by rokras
How about something like this:
这样的事情怎么样：
//p[@class='b']/following-sibling::p[following-sibling::p[@class='a'] and @class='b']
It returns all following siblings that are @class='b'and them self have following siblings with @class='a'. Though it would not work for last <p>as it does not have following siblings.
它返回所有以下兄弟姐妹，@class='b'并且他们自己有以下兄弟姐妹@class='a'。尽管它不会持续到最后，<p>因为它没有以下兄弟姐妹。
