parametrize_url() adding parameters to URLs

14^th of January 2005

I needed to write this little function because I need to add some parameters to a URL that I was going to open with urllib2. The benefit with this script is that it can combine a any URL with some structured parameters. The URL could potentially already contain a query string (aka CGI parameters). Here's how to use it if it was placed in a file called 'urlfixer.py':

>>> from urlfixer import parametrize_url
>>> parametrize_url('http://www.peterbe.com?some=thing',
any='one', tv="b b c")
'http://www.peterbe.com?some=thing&tv=b+b+c&any=one'
>>>

The function needed some extra attention (read hack) if the starting url was of the form http://foo.com?bar=xxx which is non-standard. The standard way would be http://foo.com/?bar=xxx. You can download urlfixer.py or read it here:

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

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