#!/usr/bin/python
# -*- coding: utf-8 -*-
import cookielib, urllib, urllib2
import json
from pprint import pprint

# install an urlopener which handle cookies
cookiejar = cookielib.CookieJar()
opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cookiejar))
urllib2.install_opener(opener)


class FBXComm(object):
    def __init__(self,host,passwd):
        self.__host=host
        data={"login":"freebox","passwd":passwd}

        request = urllib2.Request("http://%s/login.php"%host, urllib.urlencode(data), {})
        r=urllib2.urlopen(request)
        assert r.code == 200

        fbxsid=None
        for i in cookiejar:
            if i.name == "FBXSID":
                fbxsid=i.value.strip('"')
        assert fbxsid

    def call(self,method,data):
        cgi=method.split(".",1)[0]+".cgi"
        data={"jsonrpc":"2.0","method":method,"params":data}
        q=urllib2.Request("http://%s/%s"%(self.__host,cgi),json.dumps(data),{"Content-Type":"application/json"})
        r=urllib2.urlopen(q)
        return json.loads(r.read())

if __name__=="__main__":
    x=FBXComm("ton_ip_freebox","ton_mot_de_passe")
    pprint( x.call("conn.status",[]) )
    pprint( x.call("fs.list",["/Disque dur"]) )

Inspired from chosesafaire

More documentation on Freebox V6 apis