A python function to add/update querystring arguments on a given url

def add_get_args_to_url(url, arg_dict):
    import urllib, urlparse

    try:
        from urlparse import parse_qs
    except ImportError:
        from cgi import parse_qs

    url_parts = urlparse.urlparse(url)

    qs_args = parse_qs(url_parts[4])
    qs_args.update(arg_dict)

    new_qs = urllib.urlencode(qs_args, True)

    return urlparse.urlunparse(list(url_parts[0:4]) + [new_qs] + list(url_parts[5:]))