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Best 50 Python OOPS Interview Questions and Answers

Over time, many computer experts have grown to love Python. It’s a language that lots of companies value, and they offer opportunities to those who understand it.

Here, we’ve put together 50 Python OOPS interview questions. These questions can help you perform well in Python job interviews and provide great answers.

But before we dive into those questions, let’s start by learning the fundamentals of Python OOPS.

What is a programming language?

Programming languages are computer languages that are used to instruct the computer to perform some functions. These are languages that use syntax and keywords that are understandable by the coders/developers and are then compiled/interpreted to be converted/translated in machine language.

The flow of code:

Step 1:

The source code is sent to the compiler. 

The extension of the source could differ with the language. For example, for Python it is .py, for Java it is .java, etc.

Step 2:

The compiler then outputs the object code.

Extension of object code is .obj

The object code is then passed to a linker.

Step 3:

The linker outputs the final executable code.

Extension of the executable code is .exe

Python can be used as a Procedural Programming Language as well as an Object-Oriented Programming Language

What is Object-Oriented Programming Language and how does it benefit?

As the name suggests, Object-Oriented Programming that is popularly known as OOPS is based on the class-object model of programming.

Objects are instances of a class that contain the data and the function. Thus, the object encapsulates what function it is to perform and the data to perform with.

Object-Oriented Programming has a few key features that make it so widely used and accepted. Those features are:

Inheritance:

As the word signifies in the real-world, inheriting possessions from someone, the same concept goes with OOPS. When one class inherits data and methods from another it is called inheritance.

It is mainly used to reuse code instead of redundant coding.

Example:

As we are going to discuss Python OOPS interview questions or python coding interview questions, here is an example of inheritance using Python:

class parent_class:  

    def Summation(self,num1,num2):  

        return num1+num2;  

class child_class(parent_class):  #inheriting parent_class

    def Average(self,num1,num2): 

        return num1/num2;  

fm=child_class() 

print(fm.Average(10,20))

print(fm.Summation(78,10)) #accessing parent_class method with object of child_class

As the above example shows, the child_class is able to access the parent_class method without having to create an object for parent_class. It was done by inheritance.

If the inheritance was not implemented, the code would have required two objects for two classes.

Polymorphism:

The word literally means occurring in several forms. 

When one function is performed in multiple ways, that is called polymorphism.

Again let’s use Python code to explain this better.

class Square:

    def Area(self,side): #definiting method with 1 argument

        return side*side

class Rectangle(Square):

    def Area(self,length,bredth): #overriding method with 2 arguments

        return length*bredth

class Circle(Square):

    def Area(self,radius):

        return 2*3.14*radius*radius #overriding method with 1 argument

sqr = Square()

rct = Rectangle()

crc = Circle()

print(sqr.Area(12))

print(rct.Area(12,10))

print(crc.Area(6))

In the above example, we see that the same method Area() is being used by three classes to calculate areas of three different shapes with different arguments passed.

Data Encapsulation:

The name is self-explanatory for this concept. The idea of class encapsulating variables and objects to restrict unnecessary access.

Only an object of the class can access the data based on the access modifiers. This ensures data privacy.

Data Abstraction:

This concept ensures access to only the implementation of a function and not its internal data and function. Thus only a part of the identity of the method is exposed while keeping internal data hidden is the concept behind data abstraction. 

This increases the efficiency of code.

This is achieved with the help of abstract classes and methods.

Abstract classes and methods are only the declarations of the class or method but the implementation of these are done when inherited by another class. The definition of the abstract class or method is written in the class inheriting the abstract class or method. 

Now that we have covered the basics, let’s start with Python OOPS interview questions.

Coding interview questions often require not just the theoretical knowledge of the subject but also the knowledge to create meaningful and running codes.

List of 50 Python OOPS Interview Questions

1: What kind of a programming language is Python?

Answer: Python is basically a High-Level Object-Oriented Programming Language.

But, Python can also be used as a Procedural Language.

Python is an interpreted language i.e. it uses line-by-line execution 

2: When and by whom was it introduced?

Answer: Python was introduced in the year 1991 by a Dutch programmer Guido Van Rossum.

3: What are the advantages of using Python?

Answer: There are various advantages of Python which have made it very popular among coders/developers. A few of its advantages are:

Open-source language

Compact coding: Python can be written with very few lines of code.

Comparison:

Printing “Hello World” in Java:

public class Main{

Public static void main(System[] args){

System.out.println(“Hello World”);

}

}

Printing “Hello World” in Python:

print(“Hello World”)

It is an interpreted language which means the processing of the source code is done through an interpreter. An interpreter executes the source code line-by-line, which makes it easier to identify errors.

Python is flexible enough to be treated as a Procedural Programming Language, in case needed

Python has a very simple syntax which is quite similar to English

Example:

num = int(input())

square = (num*num)

print(square)

4: What is namespace in Python?

Answer: Imagine a dictionary of objects where the key value is the name given to the object and the value is the object itself. 

There are 3 types of namespace in Python:

1. Built-in namespace

2. Global namespace

3. Local namespace

Built-in namespace:

This contains all the objects of Python that are built-in to the Python Programming Language.

Whenever Python starts, these objects are imported and exists until the interpreter is terminated.

Below is the process of listing built-in objects in the console:

dir(__builtins__) is the command used to display the objects

Global namespace:

Global namespace are created while the execution of the main program, or when objects are included in the program using “import”.

This namespace belongs to the main program and will exist until the interpreter terminates.

Local namespace:

Whenever a function is created, Python automatically creates a namespace and that is the local namespace. This namespace exists till the function is terminated.

5:What is the significance of local and global variables in Python?

Answer: Local and global variables are kinds of variables with different scopes.

Scope: The part of the code that can access a particular variable, represents the scope of that variable. 

Local Variable:

A variable that is declared/defined within a function or class, is local to that function or class. The existence of the variable will be till the control remains within that function or class. These variables cannot be accessed from outside its scope.

For example:

def Summation():

number_first = int(input)

number_second = int(input)

sum_result = number_first + number_second

Summation() #calling the function

Thus, from the above example, we understand that number_first, number_second, and sum are local variables to the function Summation. 

It cannot be accessed from outside the function Summation.

Error shown for trying to access local variables from outside the scope is as below:

Global Variable:

When a variable is declared/defined outside of a function or class, it can be accessed from outside that function or class. Such variables fall under global variables. In other words, when a variable is not enclosed within a class or function, its scope runs throughout the program and will only cease to exist when the execution is terminated.

For example:

number_first = 5 #global variable

def Summation():

     number_second = 7

     sum_result = number_first+number_second #accessing the global variable

     print(sum_result) 

Summation() #calling the function

From the above example we see that as number_first was defined outside the function Summation, it was considered a global variable and the function Summation could access it without any error generated

6: How can Python be used?

Answer: Python can be used in many functionalities such as:

Software development , Web application development

Python has some very popular and effective web development frameworks such as Django, CherryPy, Flask, etc. 

Spotify and Mozilla are two of the widely used applications that were created using such frameworks.

  • It is hugely popular for Artificial Intelligence and Machine Learning due to its simplicity, flexibility, and stability
  • Python is also used for software testing through tools like Selenium
  • Python can connect to databases and handle files
  • Data Analytics

7: Is Python Case Sensitive?

Answer: Yes! Python is definitely case-sensitive. In other words, python distinguishes between uppercase and lowercase.

8: Why is indentation important in python?

Answer: Python does not require or involve multiple parentheses and semicolons to identify blocks of code. Indentation is used to identify the blocks and thus it is of utmost importance while coding in Python. 

This is specifically important to understand which line of code falls under which part of the block of code. While using loops and decision-making functionalities it is very important to understand which lines of code fall under the loop or decision-making block.

For example:

num = int(input)

If(num%2==0):

print(“Even Number”)

else:

print(“Odd Number”)

Observe how the indentation below ‘if’ and ‘else’ makes it clear which statement is to be executed for which decision.

for i in range (20):

print(“Line number:”+i)

Again the indentation below ‘for’ makes it clear which statement is to be repeatedly executed until the condition is being met.

In case of indentation mismatch, below is the example of the error displayed:

9: What are the limitations of Python?

We have learned a lot about the advantages and positive points of Python. But, while asking Python OOPS interview questions, the interviewer will not only be concerned about knowing how much you know of just the advantages of Python. Coding interview questions often include the shortcomings of a language and how that can be overcome. There are several aspects of coding that are not the best suit for Python and in such scenarios some other languages or approaches are required. 

Let us see how to answer such Python coding interview questions.

Answer:

Apart from the long list of advantages that Python has, there are a few shortcomings as well. Such as:

1. Speed: Python being an interpreted language, the line-by-line execution is slower than many modern-day programming languages

2. Memory Efficiency: Due to dynamic data types in Python it consumes a lot more memory space 

3. Mobile Application: Due to slow speed and high memory consumption, Python is best suited for server end programming and not mobile applications

4. Runtime Error: Due to dynamic coding, data types can throw runtime error

10: Differentiate between arrays, lists, and tuples in Python?

Let us get back to some technical Python OOPS interview questions, which may sound theoretical but the answer will be elevated with simple coding examples. 

Answer:

Differences between list, array, and tuple are:

ListArrayTuple
Mutable. That means the data can be modified, added, removed etc.Mutable. That means the data can be modified, added, removed etc.Immutable. Data in the tuple are not changeable
Enclosed in []Enclosed in []Enclosed in ()
Ordered and indexedOrdered and indexedOrdered and indexed
Can store one or many data types in a listCan store the same data type in an array. Mixed data types are not allowedCan store one or many data types in a list
In-built in Python libraryHas to be importedIn-built in Python library

Let us now see the syntax of each with examples:

List:

  <List_name> = [<values separated by comma>]

Code:

List_mixed = [‘Rose’, 12, ‘Apple’, 89.98]

print(List_mixed[0]) #prints first element of list

print(List_mixed[:]) #prints all elements of list

print(len(List_mixed)) #prints length of the list

List_mixed.append(‘Kolkata’) #adding to the list

print(List_mixed[:])

List_mixed.remove(12) #removing from the list

print(List_mixed[:])

Array:

import array as <object_name>

<Array name> = <object_name>.array[<type code>,<values separated by commas>]

Code:

Array_numbers= a.array(‘i’, [12,89,97])

Array_floats= a.array(‘f’, [ 18.00, 78.66, 56.98])

Tuple:

<tuple name> = (tuple values separated by comm)

Code:

tuple_fruits = (“Mango”, “Apple”, “Cherry”)

print(tuple_fruits)

print(tuple_fruits[1])

11: What is the lambda function?

Answer:

It is an anonymous function that accepts multiple parameters but can have only one statement.

For example:

lambda_data = lambda a,b: a*b

print(lambda_data(8,9))

12: Describe break, continue and pass keywords.

Answer:

Break:

This keyword is used to terminate the loop when a condition is fulfilled. The control is shifted out of the loop and to the next statement

Continue:

Skips one flow of the loop for a certain condition and takes the control back to the beginning of the loop to continue with the next condition checking.

Pass:

This is a null operation and helps to skip a function without facing a syntactical error. 

Example:

Break:

for i in range (12):

if(i==7):

break

else:

print(i)

Continue:

for i in range (12):

if(i==7):

continue

else:

print(i)

Pass:

for i in range (12):

pass

13: What are modifiers in Python?

Answer: Access modifiers define the accessibility of a function or class.

Functions within a class can access all the variables and functions of the same class, but other classes need permission based on the access modifiers to be able to access the functions and variables.

There are three access modifiers in Python:

Private: Private members are only accessible from within the class and not from outside. Even using objects does not allow accessing these members.

Protected: Protected members can be accessed only by child classes or subclasses of the class.

Public: Public members can be accessed from outside the class, through an object of the class. 

By default, the members of a class are public.

14:Write the functions used to convert user input into lower and upper case.

Answer:The function upper() is used to convert a string or character to an upper case

The function lower() is used to convert a string or character to lowercase

Example:

str = input()

print(str.upper())

print(str.lower())

15:What is the usage of in, is, and not operators?

Answer:

‘in’ operator is used to check if a value is within a given range. It returns true or false based on if the value is present.

Example:

for i in range(10):

print(i)

‘is’ operator checks if the operands are true and returns true or false based on the outcome.

Example:

Num1 = 56

Num2 = 78

print( Num1 is Num2)

‘not’ operator is used to reverse the result generated.

If the result is false, the not operator changes it to true.

Example:

Num1 = 10

print( not( Num1<7)

16:What is a dictionary in Python? Explain with a code

Answer:

Dictionaries in Python are used for data storage in key-value pairing.

Dictionaries are unordered and written in curly braces.

dict={

“name”: “Fname”,

“age”: “18”,

“address”: “Kolkata”

}

Print(dict)

17:What is type conversion in Python?

Answer:

Type conversion is used to manually change the data type when required. This is also called explicit type conversion.

int() = this is to convert the data type to int

float() = this is to convert the data type to float

list() = this is to convert the data type to list

str() = this is to convert the data type to string

dict() = this is to convert the data type to dictionary

18:What are functions in Python?

Answer:

Functions in python are used to perform a certain action using data. 

There are two kinds of functions:

Built-in function:

 These are functions defined in the Python library.

Example: sum(), print(), upper(), islower() etc.

User-defined:

These are customized functions written by the developer to perform required actions. 

Functions within a class are called methods.

19:What is __init__?

Answer: __init__ function is like a constructor that is created by default when a class is created. This function is used to assign values to the members of the class.

This is executed whenever a class is initiated. 

Example:

class Employee:

  def __init__(self, Fname, Lname, EmpID):

    self.First_name = Fname

    self.Last_name = Lname

    self.Employee_ID = EmpID

Emp = Employee(“FirstName”,”LastName”, 11111)

print(Emp.First_name)

print(Emp.Last_name)

20:What is self in Python?

Answer: Self represents the instance of a class and acts as the object of the class. Self is used to access the members of a class.

class Employee:

def __init__(self, Fname, Lname, EmpID):

     self.First_name = Fname

     self.Last_name = Lname

     self.Employee_ID = EmpID

As the above example shows, the self is used as an object of the class.

21: What are Python iterators?

Answer: These are objects that can be iterated or traversed.

22: How to generate random numbers in Python?

Answer: Random is used to get any random number. Random is a module that is generally used in Python for this purpose

Example:

import random

List_n=[1,8,65,13]

print(random.choice(List_n))

23: What are generators in Python?

Answer: Generators are functions that are used to generate an iterable set of items or items that can be iterated through.

24: What are assignment operators in Python?

Answer: Assignment operators are basically used to assign a value to a variable. These can also be combined with arithmetic operators to calculate and assign values at the same time.

= is used for value assigning

+= is used for assigning the summation result to the variable

-= is used for assigning difference to the variable

25: What is a map() function in Python?

Answer: Map function executes a given function to all iterable items. 

26: How do you write comments in Python?

Answer:

Comments are lines used for developers to explain a line of code without executing it.

# is used to comment a line

Example:

num = int(input()) #taking input

Print(num) #printing the value

27: Is multiple inheritance supported in Python?

Answer: Multiple inheritance is when a child class inherits multiple classes.

Python supports multiple inheritance.

class <child_class> (<parent_class1>,<parent_class2>)

We have been discussing Python OOPS interview questions in detail till now. But let’s not forget to cover the coding interview questions. When one appears for Python OOPS interview questions the interviewer will always look for opportunities to test your coding skills along with the theoretical skills. To answer Python OOPS interview questions and coding interview questions, one must have a clear idea of how to think of the most efficient logic behind solving a problem. Let us look into some coding interview questions and understand how to answer those.

Python coding interview questions:

28: Write a code to open a file.

Answer: File_open = open(“samplefile.txt”)

29: Write a code to delete a file.

Answer:

import os

if (os.path.exists(“samplefile.txt”)):

os.remove(“samplefile.txt”)

30: Write a code to calculate the number of lines in a file.

Answer:

File_open = open(“samplefile.txt”)

count = 0

text = file.read()

Text_list= text.split(“\n”)

for i in Text_list:

    if i:

        count+=1

 print (count)

31: Write a code to add values to the Python array.

Answer:

import array as arr

a = arr.array ( ‘i’ ,[ 21, 89, 77])

a.append(54)

print(a)

32: Write a code to show how classes are created, and methods are called

Answer:

class Parent():

        def summation(self):

            i=99

            j=45

            print(i+j)

p = Parent()

p.summation()

33: Write a code to show multiple inheritance in Python

Answer:

class Parent1:

    def first_parent(self):

        print(‘This is first parent class’)

class Parent2:

    def second_parent(self):

        print(‘This is second parent class’)

class ChildClass(Parent1, Parent2):

    def child_class (slef):

        print(‘This is child class’)

obj = ChildClass()

obj.first_parent()

obj.second_parent()

obj.child_class()

Now that we have answered some simple yet common coding interview questions, let us get back to answering some more of the Python oops interview questions

34: What is a package and module in Python?

Answer:

Module:

Module in Python is the collection of classes and methods that constitute one .py file. 

Whenever we write a code that makes a module.

Imagine a single file with data and functions and that is what module is to Python

The module ensures unique variable and method names.

Package:

The package is a collection of modules.

It acts as a folder that collects all modules in one place.

The package ensures unique module names.

Question 35: Explain memory management of Python.

Answer:

Python Memory Manager is responsible for creating a private memory heap space dedicated to python. All objects are stored in this heap space and are not accessible as it is private.

Python memory manager also ensures the reuse of unused spaces.

36: What is the difference between range() and xrange()?

Answer:

range() creates a static list that can be iterated through while checking some conditions. This is a function that returns a list with integer sequences.

xrange() is same in functionality as range() but it does not return a list, instead it returns an object of xrange(). xrange() is used in generators for yielding.

37: What are help() and dir() functions used for?

Answer:

help() function provides complete information of the modules, classes, and members.

When help() is called without arguments it launched a help utility that is interactive

Below is how the interactive help utility looks like:

dir() function only returns a relevant list of data of the object that is in scope. It provides more relevant information about the scope rather than complete detailed information

Example:

Code:

dir()

print(“This is dir() function”)

print(dir())

Below is the output of dir():

38: What are split() and join()?

As we are appearing for a Python code interview, it is always suggested to back our answers with proper codes. Let’s see how we can answer this with a code

Answer:

str = “Splitting and Joining in Python”

str_modify = str.split(‘ ‘)

print(str_modify)

print(‘ ‘.join(str_modify))

As we see above, the split() function is being used to split up a string base on a delimiter that is passed as the argument. With this delimiter, split() function with cut the string into multiple words from wherever it finds a space (‘ ‘)

join() function also has a delimiter mentioned as the argument which is used to recognize the point of joining the words into a string.

In other words, the split() function splits the string into multiple words based on the delimiter, and join() sews the string back together using the delimiter.

39: What is the use of negative indexing in Python?

Answer: Negative indexes simply mean from the end of the list, tuple, or string. The control goes to the very end and starts backtracking through the list, tuple, or string.

Let us see an example:

list_num = [12,98,85,25,46]

print(list_num[0]) #positive indexing to check the first element

print(list_num[1]) #positive indexing to check the second element

print(list_num[-1]) #negative indexing to check the last element

print(list_num[-2]) #negative indexing to check the second last element

The indexing for positive indexing starts with 0, the first element is counted as index 0. 

For negative indexing, the counting starts from index -1.

40: What are the different kinds of inheritances supported by Python?

Answer: There are 4 types of inheritance supported by Python. Those are as follows:

Single inheritance:

When a single parent class is inherited by a single child class, it is called Single Inheritance.

Code:

class Parent:

    def method_parent(self):

        print(“Parent Class”)

class Child(Parent):

    def method_child(self):

        print(“Child Class”)

obj = Child()

obj.method_parent()

obj.method_child()

Multi-level Inheritance:

When a parent class is inherited by a child class and the child class is again inherited by another child class, it is called Multi-level inheritance

Code:

class Parent:

    def method_parent(self):

        print(“Parent Class”)

class Child(Parent):

    def method_child(self):

        print(“Child Class”)

class Child2(Child):

    def method_child2(self):

        print(“Second Child Class”)

obj = Child2()

obj.method_parent()

obj.method_child()

obj.method_child2()

Multiple Inheritance:

When one child class inherits more than one parent class, it is called Multiple Inheritance.

Code:

class Parent:

    def method_parent(self):

        print(“Parent Class”)

class Parent2():

    def method_parent2(self):

        print(“Second Parent Class”)

class Child(Child):

    def method_child(self):

        print(“Child Class”)

obj = Child()

obj.method_parent()

obj.method_parent2()

obj.method_child()

Hierarchical Inheritance:

When one parent class is inherited by multiple child classes, it is called Hierarchical Inheritance.

Code:

class Parent:

    def method_parent(self):

        print(“Parent Class”)

class Child(Parent):

    def method_child(self):

        print(“Child Class”)

class Child2(Parent):

    def method_child2(self):

        print(“Second Child Class”)

obj = Child()

Obj2 = Child2()

obj.method_parent()

obj.method_child()

Obj2.method_parent()

Obj2.method_child2()

41: What is the use of super()?

Answer: super() is used as a temporary object of the parent class, in a child class. 

Using super(), the child class can refer to any method of the parent class.

42: What is a static method?

Answer: A static method is a method that is bound by the class itself and not the object. Accessing static methods can be done using the class name alone.

43: What is a constructor?

Answer: A constructor is a function of a class that is initiated every time a class is created. All the members of a class are initialized within the constructor. 

For JAVA or C++, the constructor is of the same name as the class but for Python, __init__() is used to invoke the constructor.

Constructors in Python can be parameterized or non-parameterized.

44: What are pandas?

Answer: Pandas is a name derived from Panel Data. This is an open-source library used for the manipulation of data.

Pandas can load data, manipulate data, analyze and prepare data.

Pandas is often used for file handling.

45: Is it possible to create an empty class in Python?

Answer: Yes! It definitely is possible. In such instances, the pass keyword is used. Pass keyword lets the control pass through.

46: What are new and override modifiers?

Answer: new modifiers state the compiler to run a new function and not use the one from the base class.

override modifier instructs to run the base class version of a class and not create a new one.

This reduces unnecessary repetitions of writing codes.

47: What is an abstract class in Python?

Answer: An abstract class acts as a template of a class that can be used by the child classes.

An abstract class cannot create any objects and can be used only by inheritance.

48: What are abstract methods?

Answer: Abstract methods are declarations of methods without proper implementation. The implementation is done when inherited into child classes and defined.

49: What is the use of len()?

Answer: len() is used to calculate the length or the number of elements in a list, array, or string.

50: What does set() do?

Answer: set() converts the iterable element into unique and distinct elements. In other words, set() helps in removing duplicate elements from an iterable.

Hopefully, these 50 Python oops interview questions will help you answer your interviewers and make a great impact throughout the interview process.

These Python oops interview questions were answered in a way that will help you answer questions related to the topics.

There might be different questions but with this set in mind, you will be able to answer any python oops interview questions that you are asked.

Conclusion on Python OOPS Interview Questions :

In conclusion, these carefully curated 50 Python OOPS interview questions serve as a comprehensive resource to help you navigate the intricacies of Object-Oriented Programming in Python.

Whether you’re a seasoned developer or a newcomer to the field, mastering these questions will undoubtedly bolster your confidence and readiness for Python interviews.

By understanding these fundamental concepts, you’ll be better equipped to showcase your expertise and secure success in your pursuit of Python-related career opportunities.

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