Object Orientated Programming

Question 1

What are classes?

Answer 1

• Classes are used as blueprints or templates that can be used to create objects in OOP
• This method allows for reusable and organised code in a modular way

Question 2

What are objects?

Answer 2

• An object is a representation of a real world entity
• A class is a blueprint that describes the properties and behaviours of objects, while an object is a specific instance created using the blueprint

Question 3

What are constructors?

Answer 3

• A special method within a class that is automatically called when an object of that class is instantiated (created)

Question 4

How is a class set up called ItemForSale with 3 attributes: itemName, price, discount

Answer 4

class ItemForSale():
def __init__ (self, itemName, price, discount):
self.__itemName = itemName
self.__price = price
self.__discount = discount

Question 5

How to add a new object to a class ItemForSale with 3 attributes

Answer 5

tank = ItemForSale(“tank”, 10, 10)

Question 6

what is a method and what are the 2 different types?

Answer 6

• A method is a function that is associated with objects or classes that define the behaviour and actions that an object can perform
• The two types are functions and procedures
• Functions: performs a task and returns a value
• Procedure: performs a task but doesn’t return a value

Question 7

Describe a public method

Answer 7

• Accessible and can be invoked by any code within the same class or from any external classes
• Changes to public methods may effect other parts of the code
• Used when you want to provide accessibility of certain functionalities of an object or class to other parts of your program

Question 8

Describe a private method

Answer 8

• Only accessed within the same class and cannot be invoked by external code or other classes
• Changes to private methods have a localised effect
• Used when you have internal implementation details that should not be accessed or used by external code

Question 9

What is an attribute?

Answer 9

• Refers to a data memory or a property associated with an object or class
• They define the state of an object and can have different values for different instances of the same class

Question 10

What is inheritence?

Answer 10

• Allows a class to inherit the properties and behaviours of another class
• Allows a derived class to inherit and utilise existing code from the base class
• The derived class “is a” base class
• E.G: the base class is vehicle and derived class is car. A car “is a” vehicle

Question 11

What is encapsulation?

Answer 11

• The practice of grouping data (attributes) and methods (functions) within a class
• Using encapsulation ensures that data remains secure and is not accidentally modified or misused by controlling access to them using access modifiers (public, private)
• It also helps to organise code by keeping related methods and data together

Question 12

What is abstraction in encapsulation?

Answer 12

• Reduces complexity by hiding the implementation details of the object, making it easier to work with and understand
• Programmers can use methods and classes from other parts of the program without having to understand how they are constructed internally

Question 13

What is polymorphism?

Answer 13

• Allows objects to take on different forms or behaviours
• Different objects can share the same name or behaviour but can work in different ways
• It helps make code more flexible, reusable and easier to manage

Question 14

What are get and set methods?

Answer 14

• A get method returns attributes of a specific object
• A set method changes the attributes of a specific object

Question 15

How would you code a get method for an ItemForSale?

Answer 15

class ItemForSale():
def __init__(self, itemName, price, discount):
self.__itemName = itemName
self.__price = price
self.__discount = discount

def getPrice(self):
     return self.\_\_price

tank.getPrice()

Question 16

What keyword is used for inheritance?

Answer 16

• Use the super(). keyword

Question 17

How would you code inheritance for an ItemForSale?

Answer 17

class tank(ItemForSale):
def __init__(self, itemName, price, discount, quantity):
super().__init__(itemName, price, discount)
self.__quantity = quantity

Question 18

What is encapsulation in terms of get methods?

Answer 18

• The get method is a type of method that is used to retrieve the value of an object’s private attributes
• The main purpose of a get method is to provide controlled access to the data of an object without allowing direct modification
• Attributes are declared as private to achieve encapsulation, so they cannot be accessed directly from outside of the class
• Instead, public get methods are used to read these attributes

Question 19

How would you code encapsulation for an ItemForSale?

Answer 19

class ItemForSale():
def __init__(self, itemName):
self.__itemName = itemName

def getItemName(self):
    return self.\_\_itemName

Question 20

What is encapsulation in terms of set methods?

Answer 20

• Set methods are used to allow controlled access by enforcing conditions or validations before updating an attribute

Question 21

What is run-time polymorphism?

Answer 21

• A subclass overrides a method defined in a superclass, and the correct version is chosen at run-time, not compile-time