9. Advanced OOP

Dunder (Magic) Methods

You can teach your objects how to behave with Python operators.

• __init__: Constructor
• __str__: String representation (for users)
• __repr__: Detailed representation (for developers)
• __eq__: Equality (==)
• __add__: Addition (+)

Composition over Inheritance

A classic engineering principle. Instead of building massive Inheritance trees, build small objects that hold other objects.

python
class Engine:
    def start(self): pass

class Car:
    def __init__(self):
        self.engine = Engine() # Has-a Engine