<?xml version="1.0"?>
<rootnode>
	<node id="1">bla-bla-bla</node>
	<node id="2">bla-bla-bla</node>
	<node id="3">bla-bla-bla</node>
</rootnode>

from xml.etree import ElementTree

doc = ElementTree.parse("file.xml")
for node in doc.getroot().findall("node"):
    if node.attrib["id"] == "2":
        print node.text
        break

from xml.etree import ElementTree as ET

dom = ET.parse("file.xml").getroot()
node = dom.find("node[@id='2']")
if node is not None:
    print(node.text)