Object Oriented Programming

Question 1

What does OOP stand for?

Answer 1

Object Oriented Programming

Question 2

True or False: In OOP, an object is an instance of a class.

Answer 2

True

Question 3

Fill in the blank: The four main principles of OOP are encapsulation, inheritance, ______, and polymorphism.

Answer 3

abstraction

Question 4

What is the purpose of encapsulation in OOP?

Answer 4

To restrict access to certain components of an object and protect its state.

All you need to know is the interface of a class to use it.

Question 5

Define inheritance in the context of OOP.

Answer 5

Inheritance allows a new class to inherit properties and methods from an existing class.

Question 6

True or False: Polymorphism allows methods to do different things based on the object that it is acting upon.

Answer 6

True

Question 7

What is a class in OOP?

Answer 7

A blueprint for creating objects that defines properties and methods.

Question 8

What does the term abstraction mean in OOP?

Answer 8

Abstraction is the concept of hiding complex implementation details and showing only the essential features of an object.

Question 9

What is the name for the process of creating an object from a class?

Answer 9

Instantiation.

Question 10

What is the purpose of a ‘getter’ method in a class?

Answer 10

They are used to access non-public attributes from a class.

See here for using the property decorator in Python instead of getter and setter methods.

Question 11

What is the purpose of a ‘setter’ method in a class?

Answer 11

To set the value of non-public attributes in a class.

See here for using the property decorator in Python instead of getter and setter methods.

Question 12

What are the advantages of using OOP to build a software program?

Answer 12

• Organisation
• Reusability - inheritance reduces the need to replicate code, reduces redundancy.
• Collaboration - developers can work on different classes simultaneously.

Question 13

What are the disadvantages of using OOP to build a software program?

Answer 13

• It can create longer programs than using a procedural approach - can slow performance.
• Greater complexity can make code more difficult to understand.

Question 14

What is the relationship between a superclass and subclass?

Answer 14

A subclass is derived from a superclass (aka base class or parent class).

Question 15

What is a helper class?

Answer 15

A class which is used to assist in providing functionality which is not the main objective of the application in which it is used.

Question 16

What is the difference between a method and a function?

Answer 16

Methods are tied to objects/classes and need an instance of an object/class to be called.
Functions are independent and can be called anywhere.

Question 17

How do you make a protected variable or method in Python?

Answer 17

By prefixing the variable or method name with _.

Question 18

What is an abstract class?

Answer 18

A class which is not instantiated, but used to define other classes.

~ a base class.

Question 19

What is a static method?

Answer 19

A method defined inside a class which has no access to anything else in the class (e.g. self)

Created using the @staticmethod decorator in Python.

Question 20

What is a class method?

Answer 20

A method defined inside a class which only has access to class variables and other class methods, not specific instance attributes.

Created using the @classmethod decorator in Python.

Question 21

Which constructor function is run every time a new instance of a class is created?

Answer 21

\_\_init\_\_()

Question 22

When are try/except blocks appropriately used in Python?

Answer 22

When an error cannot be avoided and you are aware of it, plus you have a specific plan to handle the error.

Should probably be limited to cases where taking in external data.

Question 23

How do you create a child class in Python?

Answer 23

By passing the name of the parent class in parentheses after the child class name:

def parent_class():
...
def child_class(parent_class):
...

Question 24

Liskov substitution principle

How does it apply to inheriting classes in Python?

Answer 24

Every instance of an inheriting child class is a valid instance of the parent class.

Question 25

How are subclasses of an abstract class guaranteed to contain the methods of the abstract class?

Answer 25

Because these methods must be explicitly defined inside the subclasses.

Question 26

Explain the following command seen within a child class definition: `super().__init__`

Answer 26

Call the initialisation function from the super class (parent class).

Question 27

How do you make a private variable in Python? | Private variable cannot be directly accessed outside the relevant class.

Answer 27

By prefixing the variable name with double underscore, `__`.

Question 28

What is the purpose of creating a class in OOP?

Answer 28

To bring related data and functions together, creating a blueprint for individual instances with specific attributes and methods.