python - Patterns for creating and updating related models in django -

assuming have 2 models:

class photoalbum(models.model):     name = models.charfield(max_length=255)  class photo(models.model):     album = models.foreignkey(to=photoalbum)     photo = models.imagefield(upload_to=".") 

i wish give user form, on provide "name" of album, , have logic how create album photos given name. assumed need create additional service here:

class photoalbumservice:     def __init__(self, album):         self._album = album         self._photos = list(self._album.photo_set.all())      def create(self):         # creation logic here         # common function creation , updating      def update(self):         # updating logic here         # again common function creation , updating         # additional unique logic updating      def _update_only_method(self):         # called on update      def _common_logic(self):         # common logic both create , update 

and in views.py im doing creation:

albumservice(album(name="user_provided_name")).create() 

and updating:

albumservice(album.objects.get(pk=1)).update() 

but confused, because, example, creation - dont need have list of photos (there no photo before creation) , method, used update not needed creation. - on each creation or updating - new instance of service created. i'm not satisfied behavior. maybe there useful patterns normalize such behavior?

upd

why haven't used managers? far know - managers "table-level" operations, here have several tables. updating of existing album "row-level" operation, should exist model method. think operations should coupled