Set variable to an expired session out of a view in Django

I’m trying to set a variable to an expired session out of a view in Django.

I’m aware of django’s documentation on Using sessions out of views. But in my case, I try to set a session variable in a custom management command.

Here’s what I tried :

from django.contrib.sessions.models import Session

class Command(BaseCommand):
    help = "My custom command."

    def handle(self, *args, **options):
        for s in Session.objects.all():
            s['my_variable'] = None

What I get is this error:

TypeError: 'Session' object does not support item assignment

I also tried:

[…]
ss = SessionStore(session_key=s.session_key)
ss['my_variable'] = None
ss.save()

This creates another session but does not modify the existing one…

How can I set my_variable to None ?

Edit: The session I’m trying to set a variable to is expired

You can’t do that on expired sessions. Django does not allow you.

But here is a hack:

class Command(BaseCommand):
    help = "My custom command."

    def handle(self, *args, **options):
        future = datetime.datetime(datetime.MAXYEAR, 1, 1)
        for s in Session.objects.all():
            ed = s.expire_date
            s.expire_date = future
            s.save()
            ss = SessionStore(session_key=s.session_key)
            ss['my_variable'] = None
            ss.save()
            updated_session = Session.objects.get(session_key=s.session_key)
            updated_session.expire_date = ed
            updated_session.save()