Attributes Annotations

Using annotations starting with @ symbol is a special way to define properties.

Write @property to define get() method;
Write @attribute.setter to define the set() method for the attribute.

We need to do that to explain to Python what these methods are going to be used for.


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class Cat:

  def __init__(self, name = 'Kitty', age = 1):
    self.name = name
    self.__age = age
    self.__number_of_legs = 4

  @property
  def age(self):
    return self.__age

  @age.setter
  def age(self, age):
    if isinstance(age, int) and 0<=age<=30:
      self.__age = age
    else:
      print('Invalid value of attribute age')

cat = Cat('Maggie', 3)
# Adding the wrong value
cat.age = -100 
cat.age = 5
print(cat.age)

Note

First, define getter @property and after that – setter @attribute.setter;
Both methods have the same name, that is equal to the attribute name;
Now, to access the private attribute __age outside the class, you can use the cat.age expression;

Everything was clear?

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Section 2. Chapter 3

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Course Content

Object-Oriented Programming in Python

1. Classes and Objects

Classes Objects Implementation Unique Object Constructor

2. Encapsulation

Private and Public Concepts Get and Set Attributes Annotations

3. Inheritance

Inheritance Challenge Method super()

4. Polymorphism

Polymorphism Challenge