>>> def modify_model_state(model):
...   model.state = 'Closed'
...   model.save()
...
>>> model = get_object_or_404(Model, pk=pk_object)
>>> model.state
u'Open'
>>> modify_model_state(model)
>>> model.state
u'Open'
>>> the_same_model = Model.objects.get(id=pk_object)
>>> the_same_model.state
u'Closed'
>>>