properties.md

Properties

Property decorators in Python provide a way to use getters, setters, and deleters in an object-oriented fashion. This approach allows for controlled access to class attributes, ensuring encapsulation and offering additional functionality like validation and automatic calculations.

@property

The @property decorator turns a method into a 'getter' for a class attribute. This allows the method to be accessed like an attribute, without the need to call it like a function.

class MyClass:
    def __init__(self, value):
        self._value = value

    @property
    def value(self):
        return self._value

@property.setter

The @property.setter decorator is used alongside @property. It defines a method that acts as the setter for a property, allowing for additional logic (like validation) when a property's value is set.

class MyClass:
    # ...

    @value.setter
    def value(self, new_value):
        if new_value < 0:
            raise ValueError("Value must be positive")
        self._value = new_value

@property.deleter

The @property.deleter decorator allows you to define custom behavior when a property is deleted with the del statement.

class MyClass:
    # ...

    @value.deleter
    def value(self):
        print("Value is being deleted")
        del self._value

Full Example

Here is a complete example of a class using all three decorators:

class MyClass:
    def __init__(self, value):
        self._value = value

    @property
    def value(self):
        return self._value

    @value.setter
    def value(self, new_value):
        if new_value < 0:
            raise ValueError("Value must be positive")
        self._value = new_value

    @value.deleter
    def value(self):
        print("Value is being deleted")
        del self._value

# Usage
obj = MyClass(10)
print(obj.value)  # Getter
obj.value = 20    # Setter
del obj.value     # Deleter