Property Decorator

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 10 of 64.

The @property decorator allows you to access methods like attributes, providing a clean way to get and set values.

Here is an example of a class using @property:

class Circle:
    def __init__(self, radius):
        self._radius = radius
    
    @property
    def radius(self):
        return self._radius
    
    @property
    def area(self):
        return 3.14159 * self._radius ** 2

Create a circle and access properties:

my_circle = Circle(5)

Access properties like regular attributes:

print(my_circle.radius)
print(my_circle.area)

Output:

5
78.53975

Notice you don't use parentheses () when accessing properties - they look like attributes but run method code.

Add a setter to allow changing values:

class Circle:
    def __init__(self, radius):
        self._radius = radius
    
    @property
    def radius(self):
        return self._radius
    
    @radius.setter
    def radius(self, value):
        if value > 0:
            self._radius = value
        else:
            print("Radius must be positive!")

Now you can set the radius like an attribute:

my_circle = Circle(5)
my_circle.radius = 10  # Uses the setter
print(my_circle.radius)  # Uses the getter

Output:

Key Point: @property makes methods look like attributes, while @property_name.setter allows you to control how values are assigned.

Cheat sheet

The @property decorator allows you to access methods like attributes, providing a clean way to get and set values.

Basic property usage:

class Circle:
    def __init__(self, radius):
        self._radius = radius
    
    @property
    def radius(self):
        return self._radius
    
    @property
    def area(self):
        return 3.14159 * self._radius ** 2

Access properties without parentheses:

my_circle = Circle(5)
print(my_circle.radius)  # 5
print(my_circle.area)    # 78.53975

Add a setter to control value assignment:

@radius.setter
def radius(self, value):
    if value > 0:
        self._radius = value
    else:
        print("Radius must be positive!")

Set values like attributes:

my_circle.radius = 10  # Uses the setter
print(my_circle.radius)  # Uses the getter

Try it yourself

This lesson doesn't include a code challenge.

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Object Oriented Programming

2Decorators

Introduction to DecoratorsProperty DecoratorStatic Method Decorator Class Method Decorator

5Polymorphism

Method Overriding Revisited Duck Typing Abstract Classes and Methods Interface Design Recap - Shape Calculator

8Advanced OOP Concepts

Composition vs Inheritance Mixins Static and Class Methods Class Decorators Context Managers

11Design Patterns Part 2

Command Pattern Adapter Pattern Decorator Pattern Template Method Pattern State Pattern Composite Pattern

3Class Properties

Instance vs Class Variables Property Decorators Private Attributes Recap - Bank Account Manager

6Encapsulation

Public, Protected, Private Mem Access Modifiers Information Hiding Property Decorators Advanced Recap - Student Records System

9Advanced Arguments

The *args The **kwarg

12Project: Library Management

Project Overview Book and User Classes

Borrowing System

Search Functionality

Admin Interface

Testing and Integration