CODEWITHSUNDEEP
pythondjango
David542
David542

Reputation: 110093

How to write a django-like Class ("Models") initialization

I have an object called a "TemporaryPriceReduction" that tells me information on a product that undergoes a sale. The class looks something like this:

class TPR:
    def __init__(self, product_id, territory):
        self.product_id = product_id
        self.territory = territory

In django models, it allows you to define things outside an init (at least in the specific model that inherits the models.Model base class:

class TPR(models.Model):
    product_id = ...
    territory = ...

Basically, I'd like to be able to do this:

class TPR(AbstractClass):
    product_id = product_id
    territory = territory

How could I build something like an abstract base class so that I can define things outside the init (like in django) rather than having to write the init?

Upvotes: 0

Views: 247

Answers (1)

Mad Physicist
Mad Physicist

Reputation: 114230

What you are describing is a feature of plain python, not specifically django.

When you assign self.product_id = ... in __init__, you are assigning an attribute in the instance called product_id.

When you assign product_id = ... in the class body, you are creating an attribute in the class, TPR.product_id. Instances of your class will not have such an attribute unless you explicitly assign them. Python attribute lookup works such that instance.product_id will find missing attributes in the class. That implies that all instances that do not explicitly override product_id, e.g. in __init__, share the same object as their product_id through the class.

The point is that you can define attributes using the syntax you want without doing anything special at all with base classes.

Upvotes: 1

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