How to extract xml attribute using Python ElementTree

For:

<foo>
 <bar key="value">text</bar>
</foo>

How do I get "value"?

xml.findtext("./bar[@key]")

Throws an error.

This will find the first instance of an element named bar and return the value of the attribute key.

In [52]: import xml.etree.ElementTree as ET

In [53]: xml=ET.fromstring(contents)

In [54]: xml.find('./bar').attrib['key']
Out[54]: 'value'

Getting child tag's attribute value in a XML using ElementTree

Parse the XML file and get the root tag and then using [0] will give us first child tag. Similarly [1], [2] gives us subsequent child tags. After getting child tag use .attrib[attribute_name] to get value of that attribute.

>>> import xml.etree.ElementTree as ET
>>> xmlstr = '<foo><bar key="value">text</bar></foo>'
>>> root = ET.fromstring(xmlstr)
>>> root.tag
'foo'
>>> root[0].tag
'bar'
>>> root[0].attrib['key']
'value'

If the xml content is in file. You should do below task to get the root.

>>> tree = ET.parse('file.xml')
>>> root = tree.getroot()

Your expression:

./bar[@key]

It means: bar children having key attribute

If you want to select the attribute, use this relative expression:

bar/@key

It means: the key attribute of bar children

Of course, you need to consider to use a fully compliant XPath engine like lxml.