Object Orientated Programming

Question 1

Write code to define a ‘Track’ Class which contains the title, artist and musical of the song
It also has a method of display the details for the track

Answer 1

class Track():
def \_\_init\_\_(self, title="",artist="",musical=""):
self.title = title
self.artist = artist
self.musical = musical

def showTrack(self):
print(self.title, self.artist, self.musical)

Question 2

Make an instance of the ‘Track’ Class which has a title, artist and musical instance variables

Answer 2

track1 = Track(“You’ll See”, “Adam Pascal”, 2.2)

Question 3

How do you access methods?

Answer 3

Dot notation

Question 4

Write the init subroutine in a Playlist class that contains

• An array of tracks
• A max length
• A next track value

Answer 4

Class Playlist():
def \_\_init\_\_(self,maxLength):
self.maxLength = maxLength
self.tracks = [""]*maxLength
self.nextTrack = 0

Question 5

Write an add track function on a Playlist class where newTrack is passed in and the instance variables in the class are self.maxLength, self.tracks, self.nextTrack

Answer 5

def addTrack(self,newTrack):
if self.nextTrack == self.maxLength:
print("Playlist is full")
else:
self.tracks[self.nextTrack] = newTrack
self.nextTrack = self.nextTrack + 1

Question 6

Write a delete track function on a Playlist where index in passed in and the instance variables in the class are self.maxLength, self.tracks, self.nextTrack

Answer 6

def deleteTrack(self,index):
if index > self.maxLength or index < 0:
print("Invalid index")
else:
for item in range(index, self.nextTrack-1):
self.tracks[item] = self.tracks[item+1]
end for
self.nextTrack = self.nextTrack - 1

Question 7

Write the generic code for Inheritance

Answer 7

class SubClass(SuperClass):
def \_\_init\_\_(self, attribute1, attribute2, attribute3):
SuperClass.\_\_init\_\_(self,attribute1, attribute2)
self.attribute3 = attribute3

Question 8

Write code to define a generic class with two attributes

Answer 8

class Name:
def \_\_init\_\_(self, attribute1, attribute2):
self.attribute1 = attribute1
self.attribute2 = attribute2

Question 9

Create an instance of this class called Pupil 1 with an age of 17 and a name of Heather
class Pupil:
def \_\_init\_\_(self, age, name):
self.age = age
self.name = name

Answer 9

pupil1 = Pupil(17,’Heather’)

Question 10

What is a class?

Answer 10

Blueprint of an object, definitions for the data format and avaliable procedures for a given type of object

Question 11

What is an object?

Answer 11

An instance of a class

Question 12

What is Instantiation?

Answer 12

The creation of an object from a class

Question 13

What is Inheritance?

Answer 13

Sharing of characteristics between a super class and a newly created subclass

Question 14

What are the benefits of inheritance?(1)

Answer 14

Saves development time, testing already complete, saves lines of code

Question 15

Describe Polymorphism (2)

Answer 15

A method in a sub class can be written to overwrite the method inherited by the superclass
The method called is the one in the subclass instead of the superclass

Question 16

Describe Encapsulation and give a benefit of encapsulation (2)

Answer 16

Restricting how an object’s data can be accessed

Safer, prevents unintended changing of data