我有一个cim / xml格式的xml文档。该文档包含两个名称空间
文件的一部分如下所示:
<?xml version='1.0' encoding='UTF-8'?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cim="http://iec.ch/TC57/2013/CIM-schema-cim16#">
<cim:Terminal rdf:ID="_08d0270e-f753-4812-a1cc-0550d9864a23">
<cim:IdentifiedObject.name>C:Y8CHTT402:ETTR:1</cim:IdentifiedObject.name>
<cim:Terminal.ConductingEquipment rdf:resource="#_93030a09-6aac-46b5-bf5b-f75b90841675"/>
<cim:ACDCTerminal.sequenceNumber>1</cim:ACDCTerminal.sequenceNumber>
</cim:Terminal>
<cim:Terminal rdf:ID="_5451fc7e-5d94-4d30-ab58-744ab841334d">
<cim:IdentifiedObject.name>C:Y8CHTT402:ETTR:2</cim:IdentifiedObject.name>
<cim:Terminal.ConductingEquipment rdf:resource="#_93030a09-6aac-46b5-bf5b-f75b90841675"/>
<cim:ACDCTerminal.sequenceNumber>2</cim:ACDCTerminal.sequenceNumber>
</cim:Terminal>
</rdf:RDF>
我的目标是找到一个具有给定rdf:ID 的终端etree对象。
我能够使用etree.xpath找到给定类型的所有元素。我已经找到了使用lxml documentation的方法。
from lxml import etree
root = etree.parse(my_file)
RDFNS = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
CIMNS = "http://iec.ch/TC57/2013/CIM-schema-cim16#"
all_objts = root.xpath('/y:RDF/x:Terminal' % nodeID,
namespaces={'x': CIMNS, 'y': RDFNS}) # This returns a list of all terminal objects
但是我没有获得只有一个给定rdf的元素:ID:
nodeID = "_08d0270e-f753-4812-a1cc-0550d9864a23"
tar_obj = root.xpath('/y:RDF/x:Terminal[@ID="%s"]' % nodeID,
namespaces={'x': CIMNS, 'y': RDFNS}) # Returns an empty list
我找到了a very similar post,但它没有正确回答这个问题。
我想将名称空间前缀添加到ID标记中(如下所示)
root.xpath('/y:RDF/x:PowerTransformer[y:@ID="%s"]' % nodeID,
namespaces={'x': CIMNS, 'y': RDFNS})
,但这不起作用
File "lxml.etree.pyx", line 1507, in lxml.etree._Element.xpath (src\lxml\lxml.etree.c:52198)
File "xpath.pxi", line 307, in lxml.etree.XPathElementEvaluator.__call__ (src\lxml\lxml.etree.c:152124)
File "xpath.pxi", line 227, in lxml.etree._XPathEvaluatorBase._handle_result (src\lxml\lxml.etree.c:151097)
File "xpath.pxi", line 213, in lxml.etree._XPathEvaluatorBase._raise_eval_error (src\lxml\lxml.etree.c:150950)
XPathEvalError: Invalid expression
有没有办法在具有多个名称空间的文档中使用etree.xpath搜索具有给定rdf:ID的对象?
答案 0 :(得分:1)
此表达式中的谓词存在错误:
root.xpath('/y:RDF/x:PowerTransformer[y:@ID="%s"]' % nodeID,
namespaces={'x': CIMNS, 'y': RDFNS})
您需要将[y:@ID="%s"]
更改为[@y:ID="%s"]
。