OOP

Question 1

Class

Answer 1

Defines a type of object using OOP.

each object is an instance of the class

Question 2

Attribute

Answer 2

a value within an OOP class

Question 3

OOP Method

Answer 3

procedures or functions written within an OOP class

Question 4

OOP Object

Answer 4

an independent entity
OOP defines the attributes of an object
OOP defines the methods that can be applied to the object
many instances of the object can be declared

Question 5

Constructor in OOP

Answer 5

takes place immediatelly after defining the class .
-sets attributes
- gives them starting values
- provides parameters

Question 6

write a constructor in python
(with two attributes called att1 and att2, set to the parameters p1 and p2)

Answer 6

def __init__(self, p1, p2):
self.att1=p1
self.att2=p2

Question 7

advantages of OOP

Answer 7

easier to read code

less work in long run

better control over the process

fewer erros

good for team work

Question 8

disadvantages of OOP

Answer 8

needs careful planning

more work at the start

objects must be similar

Question 9

class Car():
def__init__(self, p1, p2):
self.colour = p1
self.make = p2
self.speed = 0

create an instance of the car class called mycar that is a pink miata

Answer 9

mycar = Car(“Pink”,”Miata”)

Question 10

imagine this method is written within an OOP class:

def gofaster(self):
self.speed = self.speed + 10

in the main program, write a line of code to use this method on mycar

Answer 10

mycar.gofaster()

Question 11

rewrite this constructor in psuedocode:

class Car():
def__init__(self, p1, p2):
self.colour = p1
self.make = p2
self.speed = 0

Answer 11

class Car
procedure new(p1, p2)
colour = p1
make = p2
speed = 0
end procedure
end class

Question 12

inheritance

Answer 12

one class can “inherit” all the features of another class.

Question 13

show the first line of a class definition of a class Y that inherits class X

Answer 13

Class Y inherits X

Question 14

what do we call the class that inherits / the class it inherits from

Answer 14

super class and sub class

or

parent class and child class

Question 15

encapsulation

Answer 15

using private methods and attribites in OOP

• they cannot be altered directly, only accessed via “get” and “set” methods.

Question 16

get and set methods

Answer 16

if an attribute is private we cant show or change it in the main program, so get and set methods are used instead

Question 17

write a get method for the attribute colour in pseudocode

Answer 17

public procedure getcolour()
return colour
end procedure

Question 18

write a set method for the attribute colour in psuedocode, using p1 as the parameter

Answer 18

public procedure setcolour(p1)
colour = p1
end procedure

Question 19

What is inheritance in OOP

Answer 19

A sub class can inherit attributes and methods from an existing super - class. The subclass is then defined by making alterations or additions to the super- class.

Question 20

(psuedocode) here is a superclass.

class Employee
public procedure new(surname, jobtitle):
surname = surname
jobtitle = jobtitle
end procedure
endclass

now write a subclass for manager with their name and title, explaining which line inherits what.

Answer 20

-class manager inherits Employee
- public procedure new (thisname, thistitle)
- super.new( thisname, thistitle)

• end procedure
  -endclass

the first line inherits all the methods of the superclass

the third line inherits all attributes from the super class

Question 21

here is the pseudocode for a sub- class .

class manager inherits Employee
public procedure new (thisname, thistitle)
super.new( thisname, thistitle)

end procedure
endclass

add a line to this constructor, that will add a new attribute called “manages” and set the variable to 0 .

Answer 21

class manager inherits Employee
public procedure new (thisname, thistitle)
super.new( thisname, thistitle)
manages = 0

end procedure
endclass

Question 22

(psuedocode) here is a class defenition. Now write it in python

class Employee
public procedure new(surname, jobtitle):
surname = surname
jobtitle = jobtitle
end procedure
endclass

Answer 22

Class Employee():
def __init__(self, surname, jobtitle)
self.surname = surname
self.jobtitle = jobtitile

Question 23

here is a superclass written in python.

Class Employee():
def __init__(self, surname, jobtitle)
self.surname = surname
self.jobtitle = jobtitile

now write a subclass for manager with their name and title

Answer 23

class Manager (Employee):
def __init__(self, thisname, thistitle)
super(). __init__ (thisname, thistitle)
end procedure
endclass

Question 24

in python, write the opening line for a class constructor called car.

then, write the opening line for a class constructor called car which inherits the class vehicle

Answer 24

class Car():

class Car(Vehicle):

Question 25

in psuedocode, write the opening line for a class constructor called car.

then, write the opening line for a class constructor called car which inherits the class vehicle

Answer 25

class Car

class Car inherits Vehicle

Question 26

list 4 advantages of inheritance

Answer 26

• reduces the amount of work
• fewer new things to learn
• reduces risk of errors
• tried and tested methods

Question 27

How could inheritance be used for logins

Answer 27

The admin login class could inherit attributes of the normal login class, with extra security checks.

This reduces the amount of work the programmer has to do and reduces the risk of errors. As methods are reused

Question 28

when using inheritance, what are the 3 different options for a constructor ( the part of the definition which defines and sets attributes)

Answer 28

No constructor - use attributes of superclass

Inherit constructor - Add new attributes to build on superclass

Make a new constructor

Question 29

what is the line to inherit a constructor in python. Imagine that the attributes being inherited are colour and size

Answer 29

super(). __init__ (colour,size)

Question 30

when attributes use encapsulation, what does this mean

Answer 30

they have been made private

they cannot be shown in the main program

they cannot be changed in the main program

Question 31

is encapsulation a feature in python

Answer 31

no

Question 32

what , other tha attributes, can have encapsulation used on them

Answer 32

methods

Question 33

how to tell if encapsulation has been used in psuedocode

Answer 33

write “public” or “private” before it.

eg.
public procedure new (…)

Question 34

in pseudocode, if i wanted to make one of the attributes in a class definition private, how would i do it?

write an example of a class called shape with the colour being private

Answer 34

the same way you call global variables at the start of a module

class Shape
private colour
…. (rest of constructor)

Question 35

in the main program, i want to set the boolean attribute “verified” on user01 to true. However, it is encapsulated and needs to be accessed using a set method.

Write the single line of code

Answer 35

instead of using
user01.verified = True

use
user01.setverified(True)

Question 36

what does polymorphism mean

Answer 36

the same command has different effects with different data types or classes

eg. py + symbol is different for numerical and string variables

Question 37

how does polymorphism apply to OOP

Answer 37

A method defined for one class of object cant be used with another

A method in a different class might have the same name but do a different thing

Question 38

imagine a geometry program with classes called “square”, “triangle” and “circle”.

All of them have a method “calculate_area”

explain why this is an example of polymorphism

Answer 38

the method will work in different ways for the different classes - it will be defined with the correct formula in each class.