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'
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'