Classes

Question 1

Constructor

Answer 1

The constructor is a method that is called when an object is created
_init__

Question 2

Instance variable

Answer 2

Is defined at the instance level. It can be changed across the instances

Question 3

Class variable

Answer 3

Defined at the class level and is not expected to change

Question 4

How to call class variable

Answer 4

Object.class

Question 5

How to change class variable

Answer 5

Class.class = change

Question 6

Types of instance methods

Answer 6

Accessor and mutator methods

Question 7

How do you define class variable in the function

Answer 7

With a decorator @classmethod
And pass cls as an attribute in the function

Question 8

How to define static method

Answer 8

With a decorator @staticmethod

Question 9

What is inheritance

Answer 9

Is a mechanism that allows a class to inherit properties and behaviors from another class

Question 10

Multiple inheritance

Answer 10

Child class passes multiple parent classes as an attribute.

class C(A,B):

Question 11

How does constructor is being called with inheritance

Answer 11

1. If there is no constructor in child class, parent constrictor method is being called
2. If there is a contractor in child class, child class constructor is being called
3. To call parent constructor with child constructor:
   super().__init__()

Question 12

Types of polymorphism

Answer 12

• Duck typing
• operator overloading
• method overloading
• method overriding

Question 13

What is polymorphism

Answer 13

As the word suggests, ‘poly’ means ‘many’ and ‘morph’ points at ‘forms’; thus, polymorphism as a whole would mean ‘a property of having many forms.
One function is doing many different things

Question 14

Duck typing

Answer 14

A way of programming in which an object passed into a function or method supports all method signatures and attributes expected of that object at run time.

You do not check types at all. Instead, you check for the presence of a given method or attribute

Question 15

Operator overloading

Answer 15

Ability to define or redefine the behavior of build it operators(+,-,*,/<,>, etc) for custom objects or classes

Question 16

Method overloading

Answer 16

Two or more methods have the same name but different numbers of parameters or different types of parameters

Question 17

Method overloading implementation

Answer 17

When defining variables, account for express possible variable.
Example:
def sum(self,a=None,b=None,c=None):
s=0
if a!=None and b!=None and c!=None:
s=a+b+c
elif a!=None and b!=None:
s=a+b
else:
s=a

Question 18

Method overriding

Answer 18

When there are 2 the same methods on child and parent class, child class method takes a priority

Question 19

OOP concepts

Answer 19

Class
Objects
Polymorphism
Encapsulation
Inheritance
Data Abstraction

Question 20

What is a class in OOP

Answer 20

A class contains the blueprints or the prototype from which objects are being created.

Question 21

What is object

Answer 21

The object is an entity that has a state and behavior associated with it.

Question 22

Encapsulation

Answer 22

It describes the idea of wrapping data and the methods that work on data within one unit.

To prevent accidental change, an object’s variable can only be changed by an object’s method. Those types of variables are known as private variables.

Question 23

How to define private variable for encapsulated concept

Answer 23

self.__name = name

Question 24

How to get or change private variables from encapsulation

Answer 24

By defining a methods inside the class that returns or changes the variable

Question 25

Data abstraction OOP concept

Answer 25

It hides unnecessary code details or sensitive information from the user.

Question 26

How to create an abstract class for data abstraction OOP concept

Answer 26

from abc import ABC, abstractmethod

…..

Before method definition add decorator:
@abstractmethod