**Mixins** are exceptional examples of polymorphism, as they allow for altering the behavior and enhancing the functionality of another class. They are not meant to stand alone and lack a distinct logical context.

Extra functionality can either replace the base functionality or be supplementary to it.

Let's consider an example:

class AdminAccessMixin:
    access = "Admin"
    
    def check_access(self):
        print(f"The {self.username} has Admin Access Type")

class BlockedAccessMixin:
    access = "Blocked"
    
    def check_access(self):
        print(f"The {self.username} is blocked")

class User:
    access = "User"

    def __init__(self, username, password):
        self.username = username
        self.password = password
    
    def check_access(self):
        print(f"The {self.username} has default access")

class BlockedUser(BlockedAccessMixin, User):
    pass

class Admin(AdminAccessMixin, User):
    pass

user = User("bob111", "bob123secret")
admin = Admin("top.admin", "secret_password")
blocked_user = BlockedUser("hacker911", "qzdfaswe")

for person in [user, admin, blocked_user]:
    person.check_access()

Each `check_access()` method can have a different implementation.

Mixins allow responsibility to change functionality in the classes.

> Note
>
> - **Mixin name** should end with `Mixin`. This is the agreement of the programmers.
>
> - **Mixins** should be at the start of the inheritance order.  
`class SomeClass(FirstMixin,  LastMixin, FirstParent, LastParent)`
>
> - You can use **mixins** to add new functionality in classes.
>
> - **Mixins** are considered **dirty code** because they use attributes and methods that are not specifically intended for themselves (as mixins are designed for other classes). Therefore, using mixins is generally considered a **bad practice**, and it is better to avoid them and use them only when necessary.

This course covers Object-Oriented Programming (OOP) in Python, starting with the basics and progressing to advanced concepts. You will implement a User model to gain practical experience and understanding of OOP features. By the end of the course, you will have a strong foundation in OOP and a deeper knowledge of Python's inner workings.

Let's start! The Object-Oriented Programming basic concepts are waiting for you here! In this section, you will get acquainted with the most important concepts for understanding Object-Oriented Programming.

Inheritance - the first of the OOP principles. The entities can be inherited from other ones. You learn how it works in code here.

Inheritance - the second of the OOP principles. The attributes and methods can be closed inside the class and used by the class only. Here you learn how to code with different access modifiers.

Polymorphism and abstraction are the third and fourth of the OOP principles. These principles are not easy to understand. Here you will get to know them in the simplest ways.

The magic methods make sandbox from Python. It's a unique Python tool you can't see in other languages. Here you learn how to use these methods and about the flexibility that they bring to Python.

In-Depth Python OOP

Mixins