How to add custom parameters to an URL query string with Python?

Question

I need to add custom parameters to an URL query string using Python

Example: This is the URL that the browser is fetching (GET):

/scr.cgi?q=1&ln=0 

then some python commands are executed, and as a result I need to set following URL in the browser:

/scr.cgi?q=1&ln=0&SOMESTRING=1 

Is there some standard approach?

Answer 1

You can use urlsplit() and urlunsplit() to break apart and rebuild a URL, then use urlencode() on the parsed query string:

from urllib import urlencode from urlparse import parse_qs, urlsplit, urlunsplit  def set_query_parameter(url, param_name, param_value):     """Given a URL, set or replace a query parameter and return the     modified URL.      >>> set_query_parameter('http://example.com?foo=bar&biz=baz', 'foo', 'stuff')     'http://example.com?foo=stuff&biz=baz'      """     scheme, netloc, path, query_string, fragment = urlsplit(url)     query_params = parse_qs(query_string)      query_params[param_name] = [param_value]     new_query_string = urlencode(query_params, doseq=True)      return urlunsplit((scheme, netloc, path, new_query_string, fragment)) 

Use it as follows:

>>> set_query_parameter("/scr.cgi?q=1&ln=0", "SOMESTRING", 1) '/scr.cgi?q=1&ln=0&SOMESTRING=1' 

Answer 2

Use urlsplit() to extract the query string, parse_qsl() to parse it (or parse_qs() if you don't care about argument order), add the new argument, urlencode() to turn it back into a query string, urlunsplit() to fuse it back into a single URL, then redirect the client.