def appendBoldChanges(s1, s2):
    """Adds <b></b> tags to words that are changed"""
l1 = s1.split(' ')
l2 = s2.split(' ')
dif = list(Differ().compare(l1, l2))
return ' '.join([('<b>' + i[2:] + '</b>' if i[:1] == '+' else i[2:]) for i in
    dif if not i[:1] in '-?'])
print(appendBoldChanges('britney spirs', 'britney sprears'))
Finding differences between strings