pygtk assertion fail when using a generator to thread and callback to add elements to a treeview due to treeviewiter parent

Using the Generator class from http://unpythonic.blogspot.com/2007/08/using-threads-in-pygtk.html, the following code makes my program fail:

import gtk
import gobject
from GeneratorTask import GeneratorTask

GeneratorTask(self.get_playlist, self.load_playlist).start(playlist_id, model, iter, child)

def get_playlist(self, playlistId=None, treeModel=None, treeIter=None):
    if playlistId is None:开发者_开发百科
        yield (ten.getRootPlaylist(depth=1), treeModel, treeIter)
    else:
        yield (ten.getPlaylist(playlistId, depth=1), treeModel, treeIter)

def load_playlist(self, playlist, treeModel=None, treeIter=None):
    if treeModel == None:
        treeModel = self.programme

    # Setting treeIter = None prevents assertion fail but 
    # obviously doesn't append the items under the parent
    if len(playlist.find('childPlaylists')):
        for childPlaylist in playlist.find('childPlaylists').findall('playlist'):
            series_iter = treeModel.append(treeIter, [formatTitle(childPlaylist.find('title').text), childPlaylist.find('id').text, True, childPlaylist])
            treeModel.append(series_iter, ['Loading...', None, None, None]) 
    elif len(playlist.find('mediaList')):
        for media in playlist.find('mediaList').findall('media'):
            treeModel.append(treeIter, [media.find('title').text, media.find('id').text, False, media])

The problem seems to be passing the parent ("treeIter" in the code) looses proper reference and is no longer valid by the time the callback is called.

How can I do this properly to ensure new nodes are added under the correct parent, while still maintaining some sort of event-threading (as the ten.getPlaylist functions will block, some threading is needed)?

Just remembered, that when I was going through lablgtk tutorial, there was a hint that Gtk.tree_iters are short-lived and there was a suggestion to use Gtk.row_references instead. Sorry, this is not python, however You may find it useful: lablgtk:treeview:referring to rows