3_OPP

3. OPP

Object

Ex00

Abstract class and inheritance. See Abstract class in Python

• Abstract methots (marked with @abstractmethod) need to be reimplemented by the classes that are going to inherit from that class.
• super() allows to call the implementation of the function of the parent.

from abc import ABC, abstractmethod

class Character(ABC):
    @abstractmethod
    def __init__(self, first_name, is_alive=True):
        self.first_name = first_name
        self.is_alive = is_alive

    @abstractmethod
    def die(self):
        self.is_alive = False

class Stark(Character):
    def __init__(self, first_name, is_alive=True):
        super().__init__(first_name, is_alive)

    def die(self):
        super().die()

Ex01

• Needs to reimplement the abstract methods from ex00.
• Implementes __str__ to return str version of the class.
• Implements __repr__ to return representation of the class.
• @classmethod is a method that is bound to a class rather than its object. It doesn't require creation of a class instance, much like @staticmethod.

	classmethod	staticmethod
Definition	Method belonging to the class itself. Receives class as first argument.	Method that does not receive an implicit first argument.
Decorator	@classmethod	@staticmethod
First Parameter	cls (conventionally named)	None
Usage	Manipulating class-level variables, factory methods.	Utility functions, independent of instances or classes.
Access to Variables	Can access and modify class-level variables.	Cannot access class or instance variables.

Ex02

Multiple inheritance.

• A class that inherits from multiple classes can call any of the functions of them. Example: Baratheon.__init__(self, first_name, is_alive) calls __init__ from Baratheon class.

Ex03

Operator overload.

• __add__ for +
• __sub__ for -
• __mul__ for *
• __truediv__ for /

Ex04

Static methods (see ex01).