def getInsensitiveAttrbiute(element, key):
    keyRegex = re.compile(key, re.IGNORECASE)
for key in list(element.attrib.keys()):
    if keyRegex.match(key):
        return element.attrib[key]
raise KeyError
element = ET.fromstring('<FOO src="BAR" />')
print(getInsensitiveAttrbiute(element, 'sRc'))
Case Insensitive findall in Python ElementTree