The dynamic path for Upload_to in the Django model (Models.filefield)

Hello, in Django to version 1.4 there was the opportunity in the model for models.filefield to specify “dynamically” “The created path of storing files in the variable Upload_to

  Models.py #...  attach = models.filefield (Verbose_name = , Blank =  true , upload_to =  lambda  Instance, Filename: %(Instance.  id , filiname)     
 d django version 1.4 is like ID is assigned later and therefore Instance.id = None and also Instance.pk = None. Tell me how to point out the ID model on the way.