class ToDictMixin:
    """A mixin to add a to_dict method to a class."""
    def to_dict(self):
        return {key: value for key, value in self.__dict__.items() if not key.startswith('__')}

# Use the mixin in two different classes
class User(ToDictMixin):
    def __init__(self, username, email):
        self.username = username
        self.email = email
        self.is_active = True

class Product(ToDictMixin):
    def __init__(self, name, price):
        self.name = name
        self.price = price

# Now, both User and Product instances can use the to_dict method
user = User("john_doe", "john.doe@example.com")
print(user.to_dict())
# Output: {'username': 'john_doe', 'email': 'john.doe@example.com', 'is_active': True}

product = Product("Laptop", 1200)
print(product.to_dict())
# Output: {'name': 'Laptop', 'price': 1200}

Diff with inheritance

Normal Inheritance: Represents an "is-a" relationship. For example, a Dog "is a" Animal. The parent class defines the core functionality and attributes that are fundamental to the child class's identity.
Mixin Inheritance: Represents a "has-a" or "can-do" relationship. The mixin provides a specific, often standalone, piece of functionality that the class "has" or "can do." For example, a User class "can" be converted to a dictionary (ToDictMixin), or a DataProcessor "has" logging capability (LoggingMixin).

import logging

# Configure basic logging
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(name)s - %(levelname)s - %(message)s')

class LoggingMixin:
    """A mixin for adding logging capabilities to a class."""
    def log_info(self, message):
        logging.info(f"{self.__class__.__name__}: {message}")

class DataProcessor(LoggingMixin):
    def process_data(self, data):
        self.log_info(f"Starting to process data: {data}")
        # ... processing logic ...
        self.log_info("Finished processing data.")

class Notifier(LoggingMixin):
    def send_notification(self, message):
        self.log_info(f"Sending notification: '{message}'")
        # ... notification logic ...

processor = DataProcessor()
processor.process_data([1, 2, 3])

notifier = Notifier()
notifier.send_notification("System update complete.")