Create a field whose value is a calculation of other fields' values

Question

class PO(models.Model)
    qty = models.IntegerField(null=True)
    cost = models.IntegerField(null=True)
    total = qty * cost

How will I solve <

Answer 1

Justin Hamades answer

class PO(models.Model)
    qty = models.IntegerField(null=True)
    cost = models.IntegerField(null=True)

    @property
    def total(self):
        return self.qty * self.cost