Python ElementTree:使用XPath通过子文本查找元素 [英] Python ElementTree: find element by its child's text using XPath

问题描述

我正在尝试在其子元素之一中找到具有某些文本值的元素.例如

I'm trying to locate an element that has certain text value in one of its child. For example,

<peers>
    <peer>
        <offset>1</offset>
        <tag>TRUE</tag>
    </peer>
    <peer>
        <offset>2</offset>
        <tag>FALSE</tag>
    </peer>
</peers>

从这个XML文档中，我想直接在 offset 值为1的 peer 元素中找到 tag .

from this XML document I would like to directly locate tag in a peer element whose offset value is 1.

为此，我有一个如下所示的XPath表达式:

So for that purpose I have a XPath expression as follows:

./peers/peer[offset='1']/tag

但是在ElementTree的 Element.find()方法中使用这样的表达式会失败，并给出 None 而不是我感兴趣的"tag"元素:

however using such expression in ElementTree's Element.find() method fails and gives None rather than the "tag" element of my interest:

from xml.etree.ElementTree import fromstring

doc = fromstring("<peers><peer><offset>1</offset><tag>TRUE</tag></peer><peer><offset>2</offset><tag>FALSE</tag></peer></peers>")

tag = doc.find("./peers/peer[offset='1']/tag")

print tag


=> None

我倾向于认为这是我上面的XPath表达式错误，或者是由于ElementTree根据其文档仅支持XPath的一个子集.寻求帮助.谢谢.

I'm being inclined to believe it's either my above XPath expression is wrong, or due to ElementTree's supporting only a subset of XPath according to its documentation. Looking for help. Thank you.

推荐答案

直接使用 lxml.etree (相同的应该适用于 ElementTree )，您可以实现以下结果:

Using lxml.etree directly (the same should apply to ElementTree), you can achieve the result like this:

doc = lxml.etree.fromstring(...)
tag_elements = doc.xpath("/peers/peer/offset[text()='1']/../tag")

tag_elements 将是属于< peer> 元素的< tag> 元素的列表包含1的< offset> 元素.

tag_elements will be the list of <tag> elements belonging to <peer> elements containing an <offset> element containing 1.

给出输入(我添加了< peer> 子句以强调 tag_elements 是列表):

Given input (I've added a <peer> clause to emphasize tag_elements being a list):

<peers>
    <peer>
        <offset>1</offset>
        <tag>TRUE</tag>
    </peer>
    <peer>
        <offset>1</offset>
        <tag>OTHER</tag>
    </peer>
    <peer>
        <offset>2</offset>
        <tag>FALSE</tag>
    </peer>
</peers>

tag_elements 将包含两个元素:

for tag in tag_elements:
    print tag.text
-> TRUE
-> OTHER

更新:

doc.xpath("/peers/peer [offset = 1]/tag")也可以正常工作.

但是 doc.xpath("./peers/peer [offset = 1]/tag")不会.

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