# Django 1.8.18.dev20170123152445 documentation

# Source code for django.contrib.sessions.middleware

    import time
    from importlib import import_module

    from django.conf import settings
    from django.utils.cache import patch_vary_headers
    from django.utils.http import cookie_date

    class SessionMiddleware(object):
        def __init__(self):
            engine = import_module(settings.SESSION_ENGINE)
            self.SessionStore = engine.SessionStore

        def process_request(self, request):
            session_key = request.COOKIES.get(settings.SESSION_COOKIE_NAME, None)
            request.session = self.SessionStore(session_key)

        def process_response(self, request, response):
            """
            If request.session was modified, or if the configuration is to save the
            session every time, save the changes and set a session cookie or delete
            the session cookie if the session has been emptied.
            """
            try:
                accessed = request.session.accessed
                modified = request.session.modified
                empty = request.session.is_empty()
            except AttributeError:
                pass
            else:
                # First check if we need to delete this cookie.
                # The session should be deleted only if the session is entirely empty
                if settings.SESSION_COOKIE_NAME in request.COOKIES and empty:
                    response.delete_cookie(settings.SESSION_COOKIE_NAME,
                        domain=settings.SESSION_COOKIE_DOMAIN)
                else:
                    if accessed:
                        patch_vary_headers(response, ('Cookie',))
                    if (modified or settings.SESSION_SAVE_EVERY_REQUEST) and not empty:
                        if request.session.get_expire_at_browser_close():
                            max_age = None
                            expires = None
                        else:
                            max_age = request.session.get_expiry_age()
                            expires_time = time.time() + max_age
                            expires = cookie_date(expires_time)
                        # Save the session data and refresh the client cookie.
                        # Skip session save for 500 responses, refs #3881.
                        if response.status_code != 500:
                            request.session.save()
                            response.set_cookie(settings.SESSION_COOKIE_NAME,
                                    request.session.session_key, max_age=max_age,
                                    expires=expires, domain=settings.SESSION_COOKIE_DOMAIN,
                                    path=settings.SESSION_COOKIE_PATH,
                                    secure=settings.SESSION_COOKIE_SECURE or None,
                                    httponly=settings.SESSION_COOKIE_HTTPONLY or None)
            return response