Django, auto setting a field during a save, based on other Admin page inputs
class Suffix(models.Mode):
    suffix = models.CharField(max_length=255)
    def __unicode__(self):
        return u'%s'%(self.suffix)

class Person(models.Model):
    first_name= models.CharField(max_length=255)
    last_name= models.CharField(max_length=255)
    suffixes= models.ManyToManyField(Suffix, blank=True, null=True)
    full_name= models.CharField(max_length=255)

class SuperPerson(Person):
    ignore_this_field= model.CharField(max_length=255)

def save(self, *args, **kwargs):
    # Attempt to get data into the database so I can access it
    super(SuperPerson,self).save(*args,**kwargs)

    self.full_name = self.first_name + self.last_name
    for suf in self.suffixes.all():
        self.full_name+= suf.__unicode__()

    # Now save the copy with full_name set as I wish
    super(SuperPerson,self).save(*args,**kwargs)

@receiver(pre_save, sender=SuperPerson)
def set_full_name(sender, instance, **kwargs):
    instance.full_name = instance.first_name + instance.last_name

    for suf in instance.suffixes.all():
        instance.full_name+= ', ' + suf.__unicode__()

@receiver(m2m_changed, sender=Person.suffixes.through)
def set_full_name_after_ManyToMany_saved(sender, instance, **kwargs):
    instance.full_name = instance.first_name + instance.last_name
    for suf in instance.suffixes.all():
        instance.full_name+= ', ' + suf.__unicode__()
    print 'Saving As', instance.full_name
    instance.save()