python: interact with the session in cgi scripts

cgi, python, session

Solution

There's no "session" on `cgi`. You must roll your own session handling code if you're using raw `cgi`.

Basically, sessions work by creating a unique cookie number and sending it on a response header to the client, and then checking for this cookie on every connection. Store the session data somewhere on the server (memory, database, disk) and use the cookie number as a key to retrieve it on every request made by the client.

However `cgi` is not how you develop applications for the web in python. Use `wsgi`. Use a web framework.

Here's a quick example using cherrypy. `cherrypy.tools.sessions` is a cherrypy tool that handles cookie setting/retrieving and association with data automatically:

import cherrypy

class HelloSessionWorld(object):
    @cherrypy.tools.sessions()
    def index(self):
        if 'data' in cherrypy.session:
            return "You have a cookie! It says: %r" % cherrypy.session['data']
        else:
            return "You don't have a cookie. <a href='getcookie'>Get one</a>."
    index.exposed = True

    @cherrypy.tools.sessions()
    def getcookie(self):
        cherrypy.session['data'] = 'Hello World'
        return "Done. Please <a href='..'>return</a> to see it"
    getcookie.exposed = True

application = cherrypy.tree.mount(HelloSessionWorld(), '/')

if __name__ == '__main__':
    cherrypy.quickstart(application)

Note that this code is a `wsgi` application, in the sense that you can publish it to any `wsgi`-enabled web server (apache has `mod_wsgi`). Also, cherrypy has its own `wsgi` server, so you can just run the code with python and it will start serving on `http://localhost:8080/`

Problem

Original source