How to select data for xml Element with specific attribute value?

Question

Given:

<foo>
 <bar key="true">text1</bar>
 <bar key="false">text2</bar>
 <bar key="true">text3</bar>
 <bar key="true">text4</bar>
</foo>

I want to get the text for the bar element where the key attribute = "false".

My application is Python 2.5.5 on GAE. The XML is not true xml, but I can load it as an ElementTree and fetch data normally.

Code example:

result = urllib2.urlopen(url).read()
xml = ElementTree.fromstring(result)
str = xml.find("./bar").attrib['key']

to get the first value. I've tried various xpath queries that I think should work but I've obviously got the syntax wrong.

UPDATE:

str = xml.findtext("./bar[@key='false']")

Throws error:

  File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/xml/etree/ElementPath.py", line 93, in __init__
    "expected path separator (%s)" % (op or tag)
SyntaxError: expected path separator ([)

Solution 1

I might be wrong but I dont think that the "./bar[@key='false']" notation works in Python 2.5.5 (or at least not with the ElementTree that comes with it). I have observed the same problem in Python 2.6.5, but it does work in Python 2.7.1. I guess you will have to use another library or try the "experimental" GAE with Python 2.7.

Solution 2

This XPath will select the bar nodes whose key attribute is equal to false:

/foo/bar[@key='false']

If the current context node is the foo node then this will also work:

./bar[@key='false']

Solution 3

Based on the answer here, the XPath selector functionality was not implemented in ElementTree until version 1.3, which ships with Python 2.7, as @cdemers said.