OOP

Question 1

objects

Answer 1

instances of a class

Question 2

class

Answer 2

objects characterised by the same attributes & behaviour

Question 3

3 special methods

Answer 3

1. __init__
2. __str__ & __repr
3. __len__

Question 4

__init__

Answer 4

constructor method

Question 5

__str__

Answer 5

• str() on an object
• more readable & user-friendly
• targeted for end-users

Question 6

__repr__

Answer 6

• repr() on an object
• more detailed
• used for debugging & logging
• targeted for developers

Question 7

what are the 2 types of instance relationships

Answer 7

1. association
2. comparision

Question 8

association relationship

Answer 8

for general relationship describing when one class uses the functionalities provided by another class

Question 9

composition relationship

Answer 9

for the relationship between a whole thing & its component parts

Question 10

why do we use inheritance

Answer 10

1. model an ‘is a kind of’ relationship
2. subclasses can add more fields & methods or make changes to existing methods in the parentclass to extend behaviour

Question 11

when should we not use inheritance

Answer 11

just as a way of sharing fields & methods between classes

Question 12

syntax for inheritance

Answer 12

class subClass(SuperClass)

Question 13

superclass vs subclass

Answer 13

• subclasses can override methods from superclass to provide specific functionality
• when a method with the same name were defined in both superclass & a subclass, use super() to refer to method in superclass
• using super to reuse initialisation and other superclass’ methods helps avoid repeating code across classes

Question 14

why doesn’t comparing objects usually work

Answer 14

objects with identical values are not considered equal by default as they are not the same object and have different memory addresses