Django Model Field Default Based Off Another Field in Same Model

Question

I have a model that I would like to contain a subjects name and their initials (he data is somewhat anonymized and tracked by initials).

Right now, I wrote

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Answer 1

As an alternative implementation of Gabi Purcaru's answer, you can also connect to the pre_save signal using the receiver decorator:

from django.db.models.signals import pre_save
from django.dispatch import receiver


@receiver(pre_save, sender=Subject)
def default_subject(sender, instance, **kwargs):
    if not instance.subject_init:
        instance.subject_init = instance.subject_initials()

This receiver function also takes the **kwargs wildcard keyword arguments which all signal handlers must take according to https://docs.djangoproject.com/en/2.0/topics/signals/#receiver-functions.