lxml validation and xpath id function

[Floris Bruynooghe]

Hi

I'm trying to use the .xpath('id("foo")') function on an lxml tree but
can't get it to work.

Given the following XML: <root><child id="foo"/></root>

And it's XMLSchema:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<xs:element name="root">
<xs:complexType>
<xs:sequence>
<xs:element ref="child"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="child">
<xs:complexType>
<xs:attribute name="id" use="required" type="xs:ID"/>
</xs:complexType>
</xs:element>
</xs:schema>

Or in more readable, compact RelaxNG, form:

element root {
element child {
attribute id { xsd:ID }
}
}

Now I'm trying to parse the XML and use the .xpath() method to find
the <child/> element using the id XPath function:

from lxml import etree
schema_root = etree.parse(file('schema.xsd'))
schema = etree.XMLSchema(schema_root)
parser = etree.XMLParser(schema=schema)
root = etree.fromstring('<root><child id="foo"/></root>', parser)
root.xpath('id("foo")') --> []

I was expecting to get the <child/> element with that last statement
(well, inside a list that is), but instead I just get an empty list.
Is there anything obvious I'm doing wrong? As far as I can see the
lxml documentation says this should work.

Cheers
Floris

 

[Stefan Behnel]

I'm trying to use the .xpath('id("foo")') function on an lxml tree but
can't get it to work.

Quick follow-up: this has been answered on the lxml mailing list:

http://comments.gmane.org/gmane.comp.python.lxml.devel/3815

Stefan