🔒 HOW TO DO ABSTRACTION WITHOUT ABC

[forest owl]

AM I CORRECT IN THIS APPROACH? WHAT ELSE NEED TO DO?

class CAR:
def init(self, car_model):
self.car_model = car_model

MADE ABSTRACT FUNCTION (METHOD)

def Car_Model(self):
    pass

MADE METHODS LIKE CONCRETE FUNCTIONS IN ABC

def KeyOn(self):
    return f"{self.car_model} : STARTS..."

def Car_Acclerate(self):
    return f"{self.car_model} : ACCELERATE"

def Car_Break(self):
    return f"{self.car_model} : APPLIES BRAKE.."

def keyOFF(self):
    return f"{self.car_model} : STOPS..."

class Toyota(CAR):
def Car_Model(self):
return f"Car Model : {self.car_model}"

def KeyOn(self):
    return super().KeyOn()

def Car_Acclerate(self):
    return super().Car_Acclerate()

def Car_Break(self):
    return super().Car_Break()

def keyOFF(self):
    return super().keyOFF()

fortuner = Toyota("Fortuner")
print(fortuner.Car_Model())
print(fortuner.KeyOn())
print(fortuner.Car_Acclerate())
print(fortuner.Car_Break())
print(fortuner.keyOFF())

[hard junco]

@forest owl

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[heavy dome]

What's the reason behind this?

[tiny tulip]

Do you know how to use abc?

[forest owl]

which reason ? making ABC without ABC or what ?

[heavy dome]

making ABSTRACTION without ABC

[forest owl]

i'hv learnt it. so yes..

[forest owl]

just checking.. got an Assignment to do

[tiny tulip]

It handles everything for you. Just use it

[heavy dome]

ok..

1. NotImplementedError
2. Method Stubs with Documentation
3. Custom Metaclasses
4. init_subclass Hook
   finaly... Duck Typing

most people will go for Duck Typing

you need some examples ? @forest owl

[forest owl]

yes @heavy dome , it would be helpful ..

[tiny tulip]

decorators
decorator factories
overloading functions and methods

[heavy dome]

NotImplementedError

class Animal:
    def speak(self):
        raise NotImplementedError("Subclass must implement speak()")

class Dog(Animal):
    def speak(self):
        return "Woof!"

# Raises error if not implemented
# cat = Animal()  # Error!

Method Stubs + Docs

class Database:
    def connect(self):
        """Must be implemented by subclasses"""
        pass

class MySQL(Database):
    def connect(self):
        return "Connected!"

# Fails silently if not overridden
# db = Database()  # No error (but useless)

Custom Metaclass

class AbstractMeta(type):
    def __new__(cls, name, bases, attrs):
        if "save" not in attrs:
            raise TypeError(f"{name} must implement 'save()'")
        return super().__new__(cls, name, bases, attrs)

class Model(metaclass=AbstractMeta):
    pass

# Raises TypeError if 'save' is missing
# class User(Model): pass  # Error!
class User(Model):
    def save(self): pass  # OK

Decorator (@abstractmethod-like)

def abstractmethod(func):
    func.__is_abstract__ = True
    return func

class Shape:
    @abstractmethod
    def area(self): pass

    def __init_subclass__(cls):
        for name, method in vars(cls).items():
            if getattr(method, "__is_abstract__", False):
                raise TypeError(f"Can't instantiate {cls.__name__} without {name}()")

# Raises TypeError if 'area' is missing
# class Circle(Shape): pass  # Error!

__init_subclass__ Hook

class Plugin:
    required = ["run"]

    def __init_subclass__(cls):
        missing = [method for method in cls.required if method not in vars(cls)]
        if missing:
            raise TypeError(f"Missing required methods: {missing}")

# Raises TypeError if 'run' is missing
# class MyPlugin(Plugin): pass  # Error!
class MyPlugin(Plugin):
    def run(self): pass  # OK

Duck Typing (No Enforcement)

# No parent class! Just assume objects have the method.
def log_to_db(storage):
    storage.save()  # Crashes at runtime if .save() is missing

class DiskStorage:
    def save(self): print("Saved!")

log_to_db(DiskStorage())  # Works
# log_to_db(object())  # Fails at runtime```

these are my old notes.. hope it help u out @forest owl

[hard junco]

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