Django Model Field Default Based Off Another Field in Same Model

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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

class Subject(models.Model):

    name = models.CharField("Name", max_length=30)
    def subject_initials(self):
        return "".join(map(lambda x: "" if len(x)==0 else x[0],
                           self.name.split(" ")))
    # Next line is what I want to do (or something equivalent), but doesn"t work with
    # NameError: name "self" is not defined
    subject_init = models.CharField("Subject Initials", max_length=5, default=self.subject_initials)

As indicated by the last line, I would prefer to be able to have the initials actually get stored in the database as a field (independent of name), but that is initialized with a default value based on the name field. However, I am having issues as django models don"t seem to have a "self".

If I change the line to subject_init = models.CharField("Subject initials", max_length=2, default=subject_initials), I can do the syncdb, but can"t create new subjects.

Is this possible in Django, having a callable function give a default to some field based on the value of another field?

(For the curious, the reason I want to separate my store initials separately is in rare cases where weird last names may have different than the ones I am tracking. E.g., someone else decided that Subject 1 Named "John O"Mallory" initials are "JM" rather than "JO" and wants to fix edit it as an administrator.)

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Django Model Field Default Based Off Another Field in Same Model __del__: Questions

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

from time import sleep
sleep(0.1) # Time in seconds

Django Model Field Default Based Off Another Field in Same Model __del__: Questions

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