NULP oop introduction

NULP oop introduction

Transcript

1. Introduction into OOP in Python Hulpa Yura 2016, NULP Python course
2. “Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which are data structures that contain data, in the form of fields, o en known as a ributes; and code, in the form of procedures, o en known as methods.” Wikipedia Definition
3. Why OOP exists? To manipulate data in human readable form
4. How it is represented in Python 1. Class! 2. Instance!
5. Class definition class WarLord(object): """warlord class”"" # Methods, attributes goes here
6. Instance class WarLord(object): """warlord class”"" # Methods, attributes goes here # lord is an instance of WarLord class lord = WarLord()
7. Magic methods
8. Magic methods __init__ class ClassName(object): """warlord class""" def __init__(self, name): super(ClassName, self).__init__() self.name = name
9. __init__ Use __init__ when you need to control initialization of a new instance.
10. Magic methods __new__ class WarlordClass(object): """warlord class""" instance = None def __new__(cls, name): if cls.instance is None: cls.instance = super(WarlordClass, cls) .__new__(cls) return cls.instance
11. __new__ Use __new__ when you need to control the creation of a new instance
12. More theory __new__ is the first step of instance creation. It's called first, and is responsible for returning a new instance of your class. In contrast, __init__ doesn't return anything; it's only responsible for initializing the instance a er it's been created.
13. OOP theory
14. 1. Inheritance 2. Encapsulation 3. Polymorphism OOP features
15. “In object-oriented programming, inheritance is when an object or class is based on another object (prototypal inheritance) or class (class-based inheritance), using the same implementation (inheriting from an object or class) specifying implementation to maintain the same behavior (realizing an interface; inheriting behavior). It is a mechanism for code reuse and to allow independent extensions of the original so ware via public classes and interfaces. The relationships of objects or classes through inheritance give rise to a hierarchy. Inheritance was invented in 1967 for Simula.” Wikipedia Inheritance
16. class PLayerCharacter(object): def get_weapon(self): print 'I am trying, sir!' def war_song(self): print 'With what?' class Orc(PLayerCharacter): def get_weapon(self): print 'My Axe is ready' def war_song(self): print "For the Sauron!" class Uruk(PLayerCharacter): def get_weapon(self): print 'Broad-bladed swords are ready!' def war_song(self): print 'For the Saruman!' class MutantOrc(Orc, Uruk): pass class TestPlayers(object): def get_character_weapon(self, character): character.get_weapon() def test_character_song(self, character): character.war_song() fantasy_test = TestPlayers() orc = Orc() uruk = Uruk() fantasy_test.test_character_song(orc) fantasy_test.test_character_song(uruk) fantasy_test.get_character_weapon(orc) fantasy_test.get_character_weapon(uruk)
17. “In programming languages, encapsulation is used to refer to one of two related but distinct notions, and sometimes to the combination thereof: A language mechanism for restricting access to some of the object's components. A language construct that facilitates the bundling of data with the methods (or other functions) operating on that data” Wikipedia Encapsulation
18. class PLayerCharacter(object): def __get_weapon(self): print 'I am hidden secret weapon' def get_weapon(self): print 'My sword is ready!!!' player = PLayerCharacter() player.__get_weapon() Traceback (most recent call last): File "incapsulating.py", line 14, in <module> player.__get_weapon() AttributeError: 'PLayerCharacter' object has no attribute '__get_weapon' # But you can call it like this: player._PLayerCharacter__get_weapon() ==> 'I am hidden secret weapon'
19. “In programming languages and type theory, polymorphism is the provision of a single interface to entities of different types. A polymorphic type is one whose operations can also be applied to values of some other type, or types” Wikipedia Polymorphism
20. class PLayerCharacter(object): def get_weapon(self): pass def attack(self): pass class OrcWarior(PLayerCharacter): def get_weapon(self): print 'My Axe is ready' def attack(self): print '(Orc is atacking you with Axe)' class ElfArcher(PLayerCharacter): def get_weapon(self): print 'Arrows are ready!' def attack(self): print '(Elf is shooting you with arrow)' class TestCharacter(object): def get_character_weapon(self, character): character.get_weapon() def test_character_attack(self, character): character.attack() fantasy_test = TestCharacter() orc = OrcWarior() elf = ElfArcher() fantasy_test.get_character_weapon(orc) fantasy_test.get_character_weapon(elf) fantasy_test.test_character_attack(orc) fantasy_test.test_character_attack(elf)