How do I match contents of an element in XPath (lxml)?

问题

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'

回答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.

来源：https://stackoverflow.com/questions/2637760/how-do-i-match-contents-of-an-element-in-xpath-lxml