(CIE A2 compsci) Object-oriented programming - key theory terms + Python statements

objects

objects

items in an object-oriented program that do all the processing and each have their own specific attributes + methods (eg. object: a crop → attribute examples: type + water reqs; method example: harvesting)

object classes

provide blueprints for objects by defining common attributes + methods via constructors etc.

encapsulation

a fundamental OOP procedure that wraps attributes + methods into a single entity

info hiding

makes an object’s attributes private so they can be changed + accessed only via the setter/getter methods of the class the object belongs to

inheritance

when an existing superclass’s used to create a new subclass that inherits the superclass’s methods + attributes with the potential for at least one of either to be overridden (eg. person superclass → employee subclass)

containment

aggregating multiple classes within a single class as shown in a class diagram (more suitable than inheritance for cases where in relation to the real world an object would be contained in another object)

polymorphism

redefining a superclass’s methods for a derived subclass

overloading

repeatedly defining a method within a single class for usage in different situations (can be done in Python by changing the number of parameters in a method)

the class constructor in Python

def __init__(self,x,y,z):
>self.attribute1 = x
>self.attribute2 = y
>self.attribute3 = z
>self.attribute4 = 0
>etc.

declaring a getter method in Python

def getAttributeX(self):
>return self.attributeX

declaring a setter method in Python

def setAttributeX(self,p):
>self.attributeX = p

instantiating an object in Python

myObject = myClass(attr1value,attr2value)