python - Override save method force me to save twice in the admin thing -

working on django1.8.4

so, got models :

class occurences(models.model):     datetime = models.datetimefield()  class serie(models.model):     first_occurence = models.datetimefield(null=true, blank=true)     last_occurence = models.datetimefield(null=true, blank=true)     occurences = models.manytomanyfield(occurence, null=true, blank=true)     def save(self, *args, **kwargs):         super(series, self).save(*args, **kwargs)         self.first_occurence = self.occurences.order_by['-datetime'].first()         self.last_occurence = self.occurences.order_by['datetime'].last()         super(series, self).save(*args, **kwargs) 

working great on manage.py shell.

but use admin interface make modifications, doesn't work directly. have modify occurences field, save it, , reload resave once again @ end...

i've tried super(...).save(...) @ beginning of save function, @ beginning , @ end of (twice), @ end.

my goal able order first_occurence (or last, 1 enough).

serie.objects.order_by('first_occurence__datetime') 

because doesn't work

serie.objects.order_by('occurence__first') serie.objects.order_by('occurence__first__datetime') serie.objects.order_by('occurence__set__first') 

i don't :/

these explicit references first_occurence , last_occurence unnecessary, django orm. of functionality provide available implicitly through manytomany field occurences.

if add meta.ordering attribute occurences model, can query first , last. example:

class occurence(models.model):     datetime = models.datetimefield()      class meta:         ordering = ('datetime',)  class series(models.model):     first_occurence = models.datetimefield(null=true, blank=true)     last_occurence = models.datetimefield(null=true, blank=true)     occurences = models.manytomanyfield(occurence, null=true, blank=true)   my_series = series.objects.get(...) first = my_series.objects.earliest() latest = my_series.objects.latest() 

also, given above, able sort occurences see have latest (or earliest) occurences. example:

series_with_latest_occurences = series.objects.order_by('-occurences__datetime') series_with_earliest_occurences = series.objects.order_by('occurences__datetime')