Django session key changes on every request?

Django version is 1.2.4.
views.py

view plainprint?

1. from django.http import HttpResponse  
2. from random import choice  
3.   
4. def index(request):  
5.     x = choice([0, 1, 2])  
6.     if x == 0:  
7.         request.session['a'] = 1  
8.     elif x == 1:  
9.         request.session.flush()  
10.     return HttpResponse(request.session.session_key + ' ' + str(request.session.keys()) + ' ' + str(x), content_type='text/plain')  

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