Python descriptors explained (simple python with code)

Descriptor is an object that defines methods for getting, setting, and deleting attributes. They are a way to customize attribute access in classes.

It is any object that implements one or more of the following methods:

• __get__(self, instance, owner)
• __set__(self, instance, value)
• __delete__(self, instance)

A common use case for descriptors is to manage the access to attributes in a class. For example, they can be used to create properties, manage lazy loading, or implement computed attributes.

Let’s see an example with lazy loading with AI model.

import time

class LazyModelTrainingDescriptor:
    def __init__(self, model_name):
        self.model_name = model_name
        self.model = None
        self.trained = False

    def __get__(self, obj, objtype=None):
        if not self.model:
            print(f"Initializing and training '{self.model_name}' model...")
            self.model = self.train_model()
            self.trained = True
        else:
            print(f"Using cached '{self.model_name}' model...")

        return self.model

    def train_model(self):
        # Simulating model training which takes time
        time.sleep(5)  # Simulate training time
        return…