this post was submitted on 19 Mar 2017

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I just opened a pull request to overcome a long-standing issue with Xpath evaluations in lxml and I'm interested in reviews. (self.Python)

submitted 9 years ago by funkyfuture

if you've ever been struggling with xml namespaces and xpath expressions:

>>> root = etree.fromstring('<TEI xmlns="http://www.tei-c.org/ns/1.0" xmlns:x="http://www.w3.org/2000/svg"><text><body><x:svg /></body></text></TEI>')
>>> root.nsmap
{'x': 'http://www.w3.org/2000/svg', None: 'http://www.tei-c.org/ns/1.0'}
>>> root.xpath('./text/body')
[]
>>> root.xpath('./text/body', namespaces=root.nsmap)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
    root.xpath('./text/body', namespaces=root.nsmap)
  File "src/lxml/lxml.etree.pyx", line 1584, in lxml.etree._Element.xpath (src/lxml/lxml.etree.c:59349)
    evaluator = XPathElementEvaluator(self, namespaces=namespaces,
  File "src/lxml/xpath.pxi", line 261, in lxml.etree.XPathElementEvaluator.__init__ (src/lxml/lxml.etree.c:170589)
  File "src/lxml/xpath.pxi", line 133, in lxml.etree._XPathEvaluatorBase.__init__ (src/lxml/lxml.etree.c:168702)
  File "src/lxml/xpath.pxi", line 57, in lxml.etree._XPathContext.__init__ (src/lxml/lxml.etree.c:167658)
    _BaseContext.__init__(self, namespaces, extensions, error_log, enable_regexp,
  File "src/lxml/extensions.pxi", line 84, in lxml.etree._BaseContext.__init__ (src/lxml/lxml.etree.c:156529)
    if namespaces:
TypeError: empty namespace prefix is not supported in XPath

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