find xml element based on its attribute and change its value

You can access the attribute value as this:

from elementtree.ElementTree import XML, SubElement, Element, tostringtext = """<root>    <phoneNumbers>        <number topic="sys/phoneNumber/1" update="none" />        <number topic="sys/phoneNumber/2" update="none" />        <number topic="sys/phoneNumber/3" update="none" />    </phoneNumbers>    <gfenSMSnumbers>        <number topic="sys2/SMSnumber/1" update="none" />        <number topic="sys2/SMSnumber/2" update="none" />    </gfenSMSnumbers></root>"""elem = XML(text)for node in elem.find('phoneNumbers'):    print node.attrib['topic']    # Create sub elements    if node.attrib['topic']=="sys/phoneNumber/1":        tag = SubElement(node,'TagName')        tag.attrib['attr'] = 'AttribValue'print tostring(elem)

forget to say, if your ElementTree version is greater than 1.3, you can use XPath:

elem.find('.//number[@topic="sys/phoneNumber/1"]')

http://effbot.org/zone/element-xpath.htm

or you can use this simple one:

for node in elem.findall('.//number'):    if node.attrib['topic']=="sys/phoneNumber/1":        tag = SubElement(node,'TagName')        tag.attrib['attr'] = 'AttribValue'

For me this Elementtree snipped of code worked to find element by attribute:

import xml.etree.ElementTree as ETtree = ET.parse('file.xml')root = tree.getroot()topic=root.find(".//*[@topic='sys/phoneNumber/1']").text

I'm not familiar with xmlElementTree, but if you're using something capable of xpath expressions you can locate a node by attribute value using an expression like this:

//number[@topic="sys/phoneNumber/1"]

So, using the etree module:

>>> import lxml.etree as etree>>> doc = etree.parse('foo.xml')>>> nodes = doc.xpath('//number[@topic="sys/phoneNumber/1"]')>>> nodes[<Element number at 0x10348ed70>]>>> etree.tostring(nodes[0])'<number topic="sys/phoneNumber/1" update="none"/>\n    '