from urlparse import urlparse, urlunparse
from urllib import urlencode

def parametrize_url(url, **params):
    """ don't just add the **params because the url
    itself might contain CGI variables embedded inside
    the string. """
    url_parsed = list(urlparse(url))
    
    encoded = urlencode(params)
    qs = url_parsed[4]
    if encoded:
        if qs:
            qs += '&'+encoded
        else:
            qs = encoded
    netloc = url_parsed[1]
    if netloc.find('?')>-1:
        url_parsed[1] = url_parsed[1][:netloc.find('?')]
        if qs:
            qs = netloc[netloc.find('?')+1:]+'&'+qs
        else:
            qs = netloc[netloc.find('?')+1:]

    url_parsed[4] = qs

    url = urlunparse(url_parsed)
    return url
        

if __name__=='__main__':
    def x(u,**k):
        print parametrize_url(u, **k), "\t", u, k


    x('http://www.peterbe.com')
    x('http://www.peterbe.com/')
    x('http://www.peterbe.com/photos')
    x('http://www.peterbe.com/photos/')
    x('http://www.peterbe.com?a=A')
    x('http://www.peterbe.com/?a=A')
    x('http://www.peterbe.com/photos?a=A')
    x('http://www.peterbe.com/photos/?a=A')
    x('http://www.peterbe.com', a='A')
    x('http://www.peterbe.com/', a='A')
    x('http://www.peterbe.com/photos', a='A')
    x('http://www.peterbe.com/photos/', a='A')
    x('http://www.peterbe.com?a=A', a='A')
    x('http://www.peterbe.com/?a=A', a='A')
    x('http://www.peterbe.com/photos?a=A', a='A')
    x('http://www.peterbe.com/photos/?a=A', a='A')
    x('http://www.peterbe.com', z='Z')
    x('http://www.peterbe.com/', z='Z')
    x('http://www.peterbe.com/photos', z='Z')
    x('http://www.peterbe.com/photos/', z='Z')
    x('http://www.peterbe.com?a=A', z='Z')
    x('http://www.peterbe.com/?a=A', z='Z')
    x('http://www.peterbe.com/photos?a=A', z='Z')
    x('http://www.peterbe.com/photos/?a=A', z='Z')
    x('http://www.peterbe.com', z='Z', y='Y')
    x('http://www.peterbe.com/', z='Z', y='Y')
    x('http://www.peterbe.com/photos', z='Z', y='Y')
    x('http://www.peterbe.com/photos/', z='Z', y='Y')
    x('http://www.peterbe.com?a=A', z='Z', y='Y')
    x('http://www.peterbe.com/?a=A', z='Z', y='Y')
    x('http://www.peterbe.com/photos?a=A', z='Z', y='Y')
    x('http://www.peterbe.com/photos/?a=A', z='Z', y='Y')