Getter and setter are methods for non-direct access to the attributes:
  - `get()` (**getter**) returns the value of the private attribute;
  - `set()` (**setter**) sets the value. 


These methods are called **properties**.

You can implement them by defining two additional methods:

class Cat:
  def __init__(self, name = 'Kitty', age = 1):
    self.name = name
    self.__age = age
    self.__children = 0 

  # Getter
  def get_age(self):
    return self.__age

  # Setter
  def set_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)
# Wrong value
cat.set_age(-23) 
cat.set_age(8)
print(cat.get_age())

## Note

We added data validation inside the `set_age()` method. Only the correct integer value can be assigned to the attribute.

The first step is to understand the key statements. Classes, objects, attributes, methods...

Encapsulation provides access to the methods and attributes of the class.

Inheritance's main idea is to use already defined classes and produce new ones by improving and extending some other classes.

This OOP principle allows the user to change the parent class functionality and adapt it to the children's class.