Django session key changes on every request?

Django version is 1.2.4.
views.py

from django.http import HttpResponse
from random import choice

def index(request):
    x = choice([0, 1, 2])
    if x == 0:
        request.session['a'] = 1
    elif x == 1:
        request.session.flush()
    return HttpResponse(request.session.session_key + ' ' + str(request.session.keys()) + ' ' + str(x), content_type='text/plain')

• session.clear() method doesn't change session key.
• The session key was changed when call the session.flush() method. (eg. logout())
• If session isn't used in request, session key was changed on every request.

ref:

• Django | How to use sessions | Django documentation

First entry

Syntax highlighting

from django.http import HttpResponse

def index(request):
    return HttpResponse('OK')