The following code shows how to deal with most of type of transactions with the facebook server.

import minifb
_FbApiKey = "xxxyyyzzz..."
_FbSecret = minifb.FacebookSecret("aaabbbccc...")


def ModPythonHandler(request):
    '''FBML Canvas page receives session info from POST'''
    arguments = minifb.validate(_FbSecret, request.read())
    if arguments["added"] != "1":
        return ServeIndexNonmember()
    else:
        session_key = arguments["session_key"]
        uid = arguments["user"]
        return ServeIndex(uid, session_key)


def UserAdded(request):
    '''Facebook callback when user has added application
        gets an auth_token through post that must be converted
        into a session_key. Then lookup and send stuff to Facebook'''
    # Parse and validate posted values
    arguments = minifb.validate(_FbSecret, request.read())
    auth_token = arguments["auth_token"]
    
    # Request session_key from auth_token
    result = minifb.call("facebook.auth.getSession",
                _FbApiKey, _FbSecret, auth_token=auth_token)
    uid = result["uid"]
    session_key = result["session_key"]

    # Lookup username and details
    usersInfo = minifb.call("facebook.users.getInfo",
                    _FbApiKey, _FbSecret, session_key=session_key,
                    call_id=True, fields="name,pic_square",
                    uids=uid) # uids can be comma separated list
    name = usersInfo[0]["name"]
    photo = usersInfo[0]["pic_square"]
    
    AddUserToDatabase(uid, name, photo)

    # Set the users profile FBML
    fbml = "<p>Welcome, new user, <b>%s</b></p>" % name
    minifb.call("facebook.profile.setFBML",
                _FbApiKey, _FbSecret, session_key=session_key,
                call_id=True, uid=uid, markup=fbml)