Python Descriptors

Introduction to Python Descriptors

Descriptors are a powerful, advanced feature of Python that enable developers to manage the access and modification of object attributes. They provide a protocol consisting of three methods, __get__, __set__, and __delete__, which can be implemented to define how attributes are retrieved, modified, or deleted. Python’s built-in @property decorator is a common use case of descriptors.

The Descriptor Protocol

The descriptor protocol consists of three special methods:

• __get__(self, instance, owner): This method is used to retrieve the attribute value.
• __set__(self, instance, value): This method is used to set the attribute value.
• __delete__(self, instance): This method is used to delete the attribute.

A descriptor needs to implement at least one of these methods to be functional.

Creating a Basic Descriptor

Let's create a simple descriptor that manages an attribute value with automatic logging of access and modifications.

Using @property as a Descriptor

The @property decorator in Python is a descriptor that allows for controlled access to an attribute. It is a high-level abstraction of the descriptor protocol, providing a clean interface for implementing getters, setters, and deleters.

Advantages of Using Descriptors

Descriptors offer several benefits:

• Code Reusability: Descriptors allow attribute management logic to be reused across different classes.
• Encapsulation: Descriptors provide a mechanism to encapsulate the logic for attribute access and modification.
• Separation of Concerns: By using descriptors, the logic for managing access and modification of attributes can be separated from the main application logic.