**Constructor** is a unique method that is automatically called during object creation. This method is not obligatory to define. The object can be created with the constructor generated automatically, as we did before.
## Constructor syntax

Constructor has reserved name `__init__()`.

## Code
After the object is created, it contains `name` and `hair_color` attributes, that are created during the constructor call. 
If we don't input any values of `name` or `hair_color`, these attributes automatically have default values: `'Kitty'`, `'black'`.  

class Cat:
  def __init__(self, name = 'Kitty', hair_color = 'black'):
    self.name = name
    self.hair_color = hair_color

print(Cat)

class Cat:
  def __init__(self, name = 'Kitty', hair_color = 'black'):
    self.name = name
    self.hair_color = hair_color
    print(name, 'cat with the', hair_color, 'hair')

# An object without adding attribute values
cat1 = Cat() 
# An object with adding attribute values
cat2 = Cat('Eva', 'white') 

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.