Untitled

from BeautifulSoup import BeautifulSoup

doc = '''<html><head><title>Page title</title></head>
       <body>
       <div>
       <a href="..." title="text to highlight">Some text to highlight</a>
       <a href="..." title="text to highlight">Some other text to highlight</a>
       </div>
       </body></html>'''

def transformText(original):
    return original + '!'


soup = BeautifulSoup(doc)

for div in soup.findAll('div'):
    for link in div.findAll('a'):
        link['title'] = transformText(link['title'])

print soup.prettify()