Twitter - who follows you that you don't follow back?

from BeautifulSoup import BeautifulSoup

def main():
    friendsfl = open('friends.xml')
    followersfl = open('followers.xml')
    friendsoup = BeautifulSoup(friendsfl)
    followsoup = BeautifulSoup(followersfl)
    
    friend_list = set()
    follow_list = set()
    
    for friend in friendsoup('user'):
        friend_list.add(friend.contents[3].next)
    for follower in followsoup('user'):
        follow_list.add(follower.contents[3].next)

    print "Common:"
    for member in follow_list.intersection(friend_list):
        print member

    print
    print "Only follow you:"
    for member in follow_list.difference(friend_list):
        print member

    print
    print "Only you follow:"
    for member in friend_list.difference(follow_list):
        print member
    
    print
    print "Stats"
    print
    print "You follow, and follow you back:"
    print "%.2f" % (len(friend_list.intersection(follow_list)) / float(len(friend_list))*100),'%'

    print "Follow you, but you don't follow back:"    
    print "%.2f" % ((1-len(follow_list.intersection(friend_list)) / float(len(follow_list)))*100),'%'

if __name__ == '__main__':
    main()