I have models, objects from which can be represented as a directed graph:

from django.db import models
from django.contrib.auth.models import User

class Record(models.Model):
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=500)
    content = models.TextField()
    sequels = models.ManyToManyField('self', blank=True, symmetrical=False, through='Extend', related_name='extending')
    author = models.ForeignKey(User, on_delete=models.CASCADE)

class Extend(models.Model):
    ancestor = models.ForeignKey(Record, on_delete=models.CASCADE, related_name='+')
    descendant = models.ForeignKey(Record, on_delete=models.CASCADE, related_name='+')

    class Meta:
        constraints = [
            models.UniqueConstraint(
                name="%(app_label)s_%(class)s_unique_relationships",
                fields=["ancestor", "descendant"],
            ),
            models.CheckConstraint(
                name="%(app_label)s_%(class)s_prevent_self_extend",
                check=~models.Q(ancestor=models.F("descendant")),
            ),
        ]

Anytime a new instance of Record is created and it has a relationship with another instance through the Extend model, I would love to calculate author.user.userprofile.income attribute in the User instance. The problem is I don't know how to calculate this attribute for all the ancestors of the newly created Record which follows some rule: if the newly created Record costs 50, the first-level ancestor gets 25 and 25 goes to other ancestors, constanly being divided by 2.

I can write the formula for the first-level ancestor, but what for others?

# In case of some purchase:
class ExtendPurchase(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    items = models.ManyToManyField(Record)
    date = models.DateField(auto_now_add=True)
    cost = models.PositiveIntegerField()

    def calculate_income(self):
        for item in self.items.all():
            item.author.userprofile.income += self.cost / len(self.items.all()) / 2 # first-level; if one would like to extend more than one Record instance
            for ancestor in item.extending.all():
                ancestor.author.userprofile.income += self.cost / delimiter # I don't know what delimiter is to be written
        self.items.save()