Decorators

Decorators

Standard decorators

Three main decorators will be looked into:

1. @property
2. @classmethod
3. @staticmethod

The code, which will be used to demonstrate all of them is here and certain sections will be pasted below for illustration.

@property

This decorator is used in the class to instantiate properties of the class. Since the class is a Circle, one of the properties is a radius and the other is an area.

Click to expand the code!

  @property
  def radius(self):
      """Get value of radius"""
      return self._radius

  @radius.setter
  def radius(self, value):
      """Set radius, raise error if negative"""
      if value >= 0:
          self._radius = value
      else:
      raise ValueError("Radius must be positive")

  @property
  def area(self):
      """Calculate area inside circle"""
      return self.pi() * self.radius**2

The radius of a circle must be given to calculate the area, however, one cannot set the area of a circle without the radius. Therefore, the radius is a property of the class circle.

As the radius can have a value, it will be set with a setter method of the property decorator, in our case @radius.setter. More info on the getter, setter, & deleter methods of property here. Note, how the radius method needs to have the same name for setting the @radius.setter. If we were to use the getter & deleter methods for the radius they would have the same method name as setter.

The area doesn't need to be set and therefore doesn't have a setter method like radius.