python - Do Arithmetic Operations in Django Model itself

Question

I want to subtract two model fields in the model itself. Example :

    class Purchase(models.Model):
    
        name = models.CharField(max_length=80, unique=True)
        quantity = models.IntegerField(max_length=100, null=True)
        scheme = models.IntegerField(max_length=100, null=True)
        rate = models.IntegerField(max_length=100, null=True)
        discountPercent = models.IntegerField(max_length=100, null=True)
        discount = models.IntegerField(max_length=100, null=True)
        gst = models.IntegerField(max_length=100, null=True)
        value = models.IntegerField(max_length=100, null=True)
        date_created = models.DateTimeField(auto_now_add=True, null=True)
        product_image = models.ImageField(upload_to='product_image/', null=True, blank=True)
        FinalPrice = .....?
    
        class Meta:
            ordering = ('-date_created',)
        def __str__(self):
            return self.name

Here I want to subtract field name "rate" and "discountPercent" and store its result in a new field named "FinalPrice". I tried to do it in views but I want to it in model itself. Please Guide me for this.

Answer 1

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