Question

I want to parse HTML with lxml using XPath expressions. My problem is matching for the contents of a tag:

For example given the

<a href="http://something">Example</a>

element I can match the href attribute using

.//a[@href='http://something']

but the given the expression

.//a[.='Example']

or even

.//a[contains(.,'Example')]

lxml throws the ‘invalid node predicate’ exception.

What am I doing wrong?

EDIT:

Example code:

from lxml import etree
from cStringIO import StringIO

html = '<a href="http://something">Example</a>'
parser = etree.HTMLParser()
tree   = etree.parse(StringIO(html), parser)

print tree.find(".//a[text()='Example']").tag

Expected output is ‘a’. I get ‘SyntaxError: invalid node predicate’

Answer 1

I would try with:

.//a[text()='Example']

using xpath() method:

tree.xpath(".//a[text()='Example']")[0].tag

If case you would like to use iterfind(), findall(), find(), findtext(), keep in mind that advanced features like value comparison and functions are not available in ElementPath.

lxml.etree supports the simple path
syntax of the find, findall and
findtext methods on ElementTree and
Element, as known from the original
ElementTree library (ElementPath). As
an lxml specific extension, these
classes also provide an xpath() method
that supports expressions in the
complete XPath syntax, as well as
custom extension functions.