Mixins
A mixin is a small, focused class that provides methods to be “mixed in” to other classes via multiple inheritance. Mixins let you bundle reusable behaviors and add them to any class, keeping your code DRY and your class hierarchies clean.
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They are usually not a standalone base class, so mixins generally don’t define their own
__init__or hold persistent attributes; they assume the main class provides any needed state. -
A mixin implements one cohesive piece of functionality (e.g. logging, serialization, validation).
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Multiple Inheritance: You inherit from one “real” base class (or more) plus any number of mixin classes:
- Order matters: Python’s Method Resolution Order (MRO) determines which method is called when names collide. Always put your mixins after the primary base class in the inheritance list.
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class LoggingMixin:
def log(self, message: str) -> None:
print(f"[{self.__class__.__name__}] {message}")
import json
class JsonSerializableMixin:
def to_json(self) -> str:
# Assume `self.__dict__` holds only serializable values
return json.dumps(self.__dict__)
# Combine Them with a “Real” Class
class User(LoggingMixin, JsonSerializableMixin):
def __init__(self, name: str, email: str):
self.name = name
self.email = email
# Usage
user = User("Alice", "alice@example.com")
user.log("Created user") # → [User] Created user
print(user.to_json()) # → {"name": "Alice", "email": "alice@example.com"}
