@property, @setter, @deleter, slots

Python properties let you expose computed or validated attributes with the clean access syntax of plain attributes. Instead of person.get_age(), you write person.age — but behind the scenes, logic runs. __slots__ is a complementary feature that restricts what attributes a class can have, saving memory and preventing typos.

@property — Computed Attributes

@property turns a method into an attribute-like accessor. Callers use obj.name (no parentheses):

@<name>.setter — Validated Writes

Add a setter to allow writes, with validation:

Why private _radius? The setter uses self._radius for storage while the property is called radius. If you used self.radius in the setter, it would call the setter recursively — infinite loop.

@<name>.deleter — Cleanup on Delete

property() Function — Old Style

Before decorators, you used property() directly. You may see this in legacy code:

Read-Only Properties

A property with no setter is read-only. Writing raises AttributeError:

slots — Restricting Attributes and Saving Memory

By default, Python objects store attributes in a __dict__. With __slots__, you declare exactly which attributes the instance can have:

Memory savings: Slots replace the per-instance __dict__ with fixed-offset storage. For classes with millions of instances, this can save 30-50% memory:

slots with Inheritance

Slots and inheritance have caveats:

When to Use Properties