gistfile1.py

def shortlink_exists(s):
    ls=select(p for p in Link if p.short_link==s)[:]
    if ls:
        return ls[0]


def longlink_exists(link):
    ls= select(p for p in Link if p.long_link==link)[:]
    if ls:
        return ls[0]

def get_unique_shortlink():
    gen_shortlink= lambda length: ''.join(random.choice(string.ascii_uppercase + string.digits) for x in range(length))
    shortlink=gen_shortlink(5)
    if shortlink_exists(shortlink):
        return get_unique_shortlink()
    return shortlink

@with_transaction
def create_link(longlink, shortlink):
    return Link(long_link=longlink, short_link=shortlink)

@route("/shorturl_ajax", method="POST")
def shorturl_ajax():   

    appurl=request.url.replace("/shorturl_ajax", "/")
        
    form=ShortURLForm(request.POST)
    longlink=form.long_link.data
    
    link=longlink_exists(longlink)
    if link:
        #print "ALREADY EXISTS...."
        return dict(data='<a href="/%s">%s</a>'%(link.short_link,appurl+link.short_link), success=True)
    else:
        #print "CREATING NEW LINK..."
        shortlink=get_unique_shortlink()
        l=create_link(longlink, shortlink)
        return dict(data='<a href="/%s">%s</a>'%(l.short_link, appurl+l.short_link), success=True)