from django import newforms as forms
from django.contrib import auth

class LoginForm(forms.Form):
  username = forms.CharField(...)
  password = forms.CharField(...)
  remember_me = forms.BooleanField(...)

  user_cache = None

  ...

  def save(self, request):
  cd = self.cleaned_data
  user = self.user_cache

  auth.login(request, user)

  if not 'remember_me' in cd or not cd['remember_me']:
  <strong>request.session.set_expire(0)</strong>

  return user