Python pickling error when using sessions

Question

In my django app I was creating an extended user profile using session vars. But when registration form was saved and user was about to create, I got following error :

Traceback (most recent call last):

  File "\Python26\Lib\site-packages\django\core\servers\basehttp.py", line 279, in run
    self.result = application(self.environ, self.start_response)

  File "\Python26\Lib\site-packages\django\core\servers\basehttp.py", line 651, in __call__
    return self.application(environ, start_response)

  File "\Python26\Lib\site-packages\django\core\handlers\wsgi.py", line 245, in __call__
    response = middleware_method(request, response)

  File "\Python26\Lib\site-packages\django\contrib\sessions\middleware.py", line 36, in process_response
    request.session.save()

  File "\Python26\Lib\site-packages\django\contrib\sessions\backends\db.py", line 53, in save
    session_data = self.encode(self._get_session(no_load=must_create)),

  File "\Python26\Lib\site-packages\django\contrib\sessions\backends\base.py", line 88, in encode
    pickled = pickle.dumps(session_dict, pickle.HIGHEST_PROTOCOL)

PicklingError: Can't pickle <type 'cStringIO.StringO'>: attribute lookup cStringIO.StringO failed

I've googled for an answer, but found nothing interesting. Any workarounds for this ?

Answer 1

It appears you have a cStringIO object in your session (perhaps an uploaded file?), these cannot be pickled. Either write custom pickling code or make sure all your session data can be serialized.

Answer 2

Something weird going on here, because the error refers to cStringIO.StringO whereas the class is actually cStringIO.StringIO, with an extra I. Have you misspelled the name somewhere?