gistfile1.py

from lxml.html import parse

def get_feed(url):
    """
    Find the first link to an XML feed (rss or atom) and return the URL
    """
    page = parse(url).getroot()
    page.make_links_absolute()
    for link in page.head.findall('links'):
        if link.get('type', '').lower() in ('application/rss+xml', 'application/atom+xml'):
            return link.get('href')