How Does the `@property` Decorator Function in Python?

How the @property Decorator Works in Python

The @property decorator is a powerful tool for creating read-only or read-write attributes on Python classes. It simplifies the creation of properties by wrapping them in a decorator function.

How the Built-in Property Decorator Works

The built-in property() function creates a descriptor object. This object has three methods:

• getter: A function that returns the value of the property.
• setter: A function that sets the value of the property.
• deleter: A function that deletes the property.

When used as a decorator, property() takes a function as its argument. This function becomes the getter for the property.

How the Decorator @property Works

The @property decorator is just syntactic sugar for the following code:

def foo(self): return self._foo
foo = property(foo)

The @decorator syntax replaces the function being decorated with the special property() descriptor object.

Creating Properties with Decorators

To create properties with decorators:

class C:
    @property
    def x(self):
        return self._x

    @x.setter
    def x(self, value):
        self._x = value

    @x.deleter
    def x(self):
        del self._x

• The @property decorator creates a getter function and attaches it to the _x property.
• The @x.setter decorator creates a new property object, replacing the getter with the decorated setter function.
• The @x.deleter decorator creates a new property object, replacing the getter with the decorated deleter function.

In-Depth Understanding

The property() function returns a special descriptor object. This object has extra methods, including getter, setter, and deleter. These methods are also decorators, which allow you to incrementally construct a full-on property object.

The syntax of the property decorator allows you to create properties with chained setter and deleter decorators. The resulting property object is then attached to the class as a descriptor, enabling attribute getting, setting, and deletion with custom behavior.

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