如何使用XPath通过其同级节点的属性来发现XMLnode？

Question

假设我有以下XML文件（可有可无的部分用“…”标记）：

<?xml version="1.0" encoding="ISO-8859-1"?>
<PARAMETERS version="1.6.2" xsi:noNamespaceSchemaLocation="http://open-ms.sourceforge.net/schemas/Param_1_6_2.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <NODE name="info" description="">
    <ITEM name="version" value="2.0.0" type="string" description="" required="false" advanced="false" />
    <ITEM name="num_vertices" value="5" type="int" description="" required="false" advanced="false" />
    <ITEM name="num_edges" value="4" type="int" description="" required="false" advanced="false" />
    <ITEM name="description" value="&lt;![CDATA[]]&gt;" type="string" description="" required="false" advanced="false" />
  </NODE>
  <NODE name="vertices" description="">
    <NODE name="0" description="">
      <ITEM name="recycle_output" value="false" type="string" description="" required="false" advanced="false" />
      <ITEM name="toppas_type" value="input file list" type="string" description="" required="false" advanced="false" />
      <ITEMLIST name="file_names" type="string" description="" required="false" advanced="false">
        <LISTITEM value="input_data/STD_MIX_1_25_neg.mzML"/>
      </ITEMLIST>
      <ITEM name="x_pos" value="-1680" type="double" description="" required="false" advanced="false" />
      <ITEM name="y_pos" value="-620" type="double" description="" required="false" advanced="false" />
    </NODE>
    <NODE name="1" description="">
    ...
    </NODE>
    ...
  </NODE>
</PARAMETERS>

我的目标是创建一个XPath查询，返回具有属性name=“file\u names”的ITEMLIST节点和具有属性name=“toppas\u type”、value=“input file list”的同级ITEM节点。我试过以下方法：

'./NODE/NODE[ITEM[@name="toppas_type"][@value="input file list"]]/ITEMLIST[@name="file_names"]'

与xml.etree.ElementTree文件在Python3.4中，但我得到一个错误“invalid predicate”。我想我的查询包含一个愚蠢的错误，但我找不到它。你知道吗

Answer 1

xml.etree.ElementTree有一个limited XPath support：

This module provides limited support for XPath expressions for locating elements in a tree. The goal is to support a small subset of the abbreviated syntax; a full XPath engine is outside the scope of the module.

如果您可以切换到^{}，可以使用^{}轴来解决：

//ITEM[@name = 'toppas_type' and @value = 'input file list']/following-sibling::ITEMLIST[@name = 'file_names']