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You want to test for element.startswith('LOCATION: ').  You are doing 'LOCATION' in element, which is not only slower since it has to check at every position of every element, it might also lead to false matches.

Also, element and data are poor names.  I suggest header and headers, respectively.

My suggestion:

LOC = 'LOCATION: '
xmllinks = [header[len(LOC):] for header in headers if header.startswith(LOC)]
if xmllinks:
    xmllink = xmllinks[0]