Python 3 Deep Dive Part 4 Oop [new] Review

Most developers use __init__ to initialize objects, but __init__ is not the constructor. The actual constructor is __new__ . The Lifecycle Pipeline

# Fragile base class problem class LoggedDict(dict): def __setitem__(self, key, value): print(f"Setting key=value") super().__setitem__(key, value)

class LifecycleDemo: def __new__(cls, *args, **kwargs): print("1. __new__ creates the raw object instance") instance = super().__new__(cls) return instance def __init__(self, value): print("2. __init__ customizes the newly created instance") self.value = value obj = LifecycleDemo(42) Use code with caution. Advanced Use Case: The Singleton Pattern

Now you can discover and execute all plugins dynamically. python 3 deep dive part 4 oop

The journey begins with the instantiation process. While most developers are familiar with , the "Deep Dive" explores

class Plugin(metaclass=PluginMeta): @abstractmethod def run(self): pass

my_car = Car("Red", "Toyota", 2015) print(my_car.color) # Output: Red my_car.honk() # Output: Honk! Most developers use __init__ to initialize objects, but

When Python executes a class block, the following happens:

class Countdown: def __init__(self, start): self.start = start def __iter__(self): return self def __next__(self): if self.start <= 0: raise StopIteration self.start -= 1 return self.start + 1

def honk(self): print("Honk!")

: Making the case for enums, customizing them, and exploring the inheritance-based nature of Python exceptions.

Inheritance is a fundamental concept in OOP that allows one class to inherit the attributes and methods of another class. The class that is being inherited from is called the parent or superclass, and the class that is doing the inheriting is called the child or subclass.

The journey into advanced OOP begins with reframing how you perceive a class. It is not merely a blueprint for an object; in Python, a class is itself an object—an instance of a type . Understanding this distinction between (data shared across all instances) and instance attributes (data unique to each object) is foundational. __new__ creates the raw object instance") instance = super()

Mastering these concepts allows you to:

If you want to learn more about OOP in Python 3, here are some recommended resources: