Question

我的XML文件看起来像这样：

<SCAN_LIST_OUTPUT>
  <RESPONSE>
    <DATETIME>2018-05-21T11:29:05Z</DATETIME>
    <SCAN_LIST>
      <SCAN>
        <REF>scan/1526727908.25005</REF>
        <TITLE><![CDATA[ACRS_Scan]]></TITLE>
        <LAUNCH_DATETIME>2018-05-19T11:05:08Z</LAUNCH_DATETIME>
      </SCAN>
      <SCAN>
        <REF>scan/1526549903.07613</REF>
        <TITLE><![CDATA[testScan]]></TITLE>
        <LAUNCH_DATETIME>2018-05-17T09:38:23Z</LAUNCH_DATETIME>
      </SCAN>
    </SCAN_LIST>
  </RESPONSE>
</SCAN_LIST_OUTPUT>

现在，当我尝试使用绝对路径找到第一个元素的REF元素时，我知道LAUNCH_DATETIME，它给出了一个错误，指出无效谓词。这是我的代码：

import xml.etree.ElementTree as ET

tree = ET.ElementTree(ET.fromstring(response))
groot = tree.getroot()
path = './/REF[../LAUNCH_DATETIME="2018-05-19T11:05:08Z"]'
scan_id = tree.find(path)

以下是回溯调用：

KeyError: ('.//REF[../LAUNCH_DATETIME="2018-05-19T11:05:08Z"]', None)

During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/home/doomsday/PycharmProjects/untitled/venv/ScanList.py", line 44, in <module>
    scan_id = tree.find(path)
  File "/usr/lib/python3.5/xml/etree/ElementTree.py", line 651, in find
    return self._root.find(path, namespaces)
  File "/usr/lib/python3.5/xml/etree/ElementPath.py", line 298, in find
    return next(iterfind(elem, path, namespaces), None)
  File "/usr/lib/python3.5/xml/etree/ElementPath.py", line 277, in iterfind
    selector.append(ops[token[0]](next, token))
  File "/usr/lib/python3.5/xml/etree/ElementPath.py", line 233, in prepare_predicate
    raise SyntaxError("invalid predicate")
SyntaxError: invalid predicate

当我在在线xpath评估器上使用相同的绝对路径时，它会为我提供所需的输出。但是当我在我的代码中尝试相同时，它失败了。如果有人能分辨出问题是什么以及如何解决问题，那就太好了。

提前致谢。

Answer 1

ElementTree的xpath support是有限的。不要尝试在..的谓词中使用REF返回树，而是将谓词添加到SCAN。

示例...

path = './/SCAN[LAUNCH_DATETIME="2018-05-19T11:05:08Z"]/REF'

无法使用Python在XML中基于绝对路径定位元素

1 个答案: