Over time, many computer experts have grown to love Python. Many companies value it and 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 used to instruct the computer to perform certain functions. They use syntax and keywords that the coders/developers understand and are then compiled/interpreted to be converted/translated into machine language.
The flow of code:
Step 1:
- The source code is sent to the compiler.
- The extension of the source could differ depending on 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.
- The extension of the executable code is .exe
- Python can be used as a procedural programming language or object-oriented programming language.
What is Object-Oriented Programming Language, and how does it benefit?
As the name suggests, Object-Oriented Programming, popularly known as OOPS, is based on the class-object programming model.
Objects are instances of a class that contain the data and the function. Thus, the object encapsulates the function it is to perform and the data it is to perform with.
Object-oriented programming has a few key features that make it widely used and accepted. Those features are:
Inheritance:
In the real world, inheritance signifies inheriting possessions from someone. The same concept applies to 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 can access the parent_class method without creating an object for the parent_class. This was done by inheritance.
If the inheritance had not been 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,breadth): #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 three classes use the same method, Area(), to calculate the 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, ensuring 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 method’s identity is exposed while keeping internal data hidden. This 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; the implementation is 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 theoretical knowledge of the subject and the knowledge to create meaningful and running codes.
List of 50 Python OOPS Interview Questions
Section 1: Basic Python OOPs Interview Questions for Freshers
1: What kind of a programming language is Python?
Answer:
- Python is basically a High-Level Object-Oriented Programming Language.
- 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 1991 by a Dutch programmer, Guido Van Rossum.
3: What are the advantages of using Python?
Answer: Python has various advantages, making 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, making it easier to identify errors.
Python is flexible enough to be treated as a Procedural Programming Language in case it is needed
Python has a very simple syntax, which is quite similar to that of English
Example:
num = int(input())
square = (num*num)
print(square)
4: What are the limitations of Python?
We have learned a lot about the advantages and positive points of Python. However, while asking Python OOPS interview questions, the interviewer will not only be concerned about knowing how much you know but also about 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 suited 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 Python’s long list of advantages, there are also a few shortcomings. 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
5: How can Python be used?
Answer: Python can be used in many functionalities, such as Software and web application development. Python has 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
6: Is Python Case Sensitive?
Answer: Yes! Python is case-sensitive. In other words, python distinguishes between uppercase and lowercase.
7: Why is indentation important in Python?
Answer: Python does not require or involve multiple parentheses and semicolons to identify code blocks. Indentation is used to identify the blocks, and thus, it is of the utmost importance while coding in Python.
It is important to understand which line of code falls under which part of the code block. 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 will be executed for which decision.
for i in range (20):
print(“Line number:”+i)
Again, the indentation below ‘for’ makes it clear which statement will be repeatedly executed until the condition is met.
Section 2: Python Syntax and Operations Interview Questions
8: 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 three types of namespace in Python:
1. Built-in namespace
2. Global namespace
3. Local namespace
Built-in namespace: This contains all the Python objects built into the Python programming language. Whenever Python starts, these objects are imported and exist 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 namespaces are created during 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, which is the local namespace. This namespace exists until the function is terminated.
9: 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 declared/defined within a function or class is local to that function or class. The variable will exist until 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.
The error shown for trying to access local variables from outside the scope is as follows:
Global Variable: When a variable is declared/defined outside a function or class, it can be accessed 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.
10: What is type conversion in Python?
Answer: Type conversion is used to change the data type when required manually. 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
11: What is the usage of in, is, and not operators?
Answer: The ‘in’ operator checks if a value is within a given range. It returns true or false based on whether the value is present.
Example:
for i in range(10):
print(i)
The ‘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)
The ‘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)
12: Write the functions used to convert user input into lower and upper case.
Answer: The function upper() converts 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())
13: What is the lambda function?
Answer: An anonymous function accepts multiple parameters but can have only one statement.
For example:
lambda_data = lambda a,b: a*b
print(lambda_data(8,9))
14: Describe break, continue and pass keywords.
Answer:
Break: This keyword terminates the loop when a condition is fulfilled. The control is shifted out of the loop to the next statement.
Continue: This function skips one flow of the loop for a certain condition and returns the control 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
15: What are assignment operators in Python?
Answer: Assignment operators are 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 differences to the variable
16: What are split() and join()?
As we are appearing for a Python code interview, it is always suggested that we 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 used to split up a string base on a delimiter 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 recognise 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.
17: 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 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 counts as index 0
For negative indexing, the counting starts from index -1
Section 3: Python Object-Oriented Programming (OOP) Concepts
18:What are functions in Python?
Answer: Functions in Python are used to perform certain actions 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: The developer writes These customised functions to perform the required actions. Functions within a class are called methods.
19:What is __init__?
Answer: The __init__ function is like a constructor created by default when a class is created. It assigns values to the class members. 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: The 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 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. Still, other classes need permission based on the access modifiers 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.
22: 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.
23: What is a constructor?
Answer:
- A constructor is a class function initiated every time a class is created. All the members of a class are initialised within the constructor.
- For JAVA or C++, the constructor has the same name as the class, but for Python, __init__() is used to invoke the constructor.
- Constructors in Python can be parameterised or non-parameterized.
24: 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 objects and can be used only by inheritance.
25: What are abstract methods?
Answer: Abstract methods are declarations of methods without proper implementation. The implementation is done when inherited and defined into child classes.
26: 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.
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>)
28: What are Python Iterators?
In Python, an iterator is an object that can be iterated (looped) upon. Iterators are implemented using two primary methods: __iter__() and __next__().
- __iter__(): This method initialises the iterator. It is called once and returns the iterator object itself.
- __next__(): This method retrieves the next value from the iterator. When there are no more items to return, it raises a StopIteration exception to signal the end of the iteration.
29: What are generators in Python?
Answer: Generators are a simple and powerful tool for creating iterators. They allow you to iterate lazily over a sequence of values, producing items only as needed. Generators are implemented using functions and the yield statement.
Key Features of Generators
- Lazy Evaluation: Generators produce items one at a time and only when required, which makes them memory efficient.
- State Preservation: Generators automatically preserve their state between each yield, making it easier to write complex iteration logic.
Section 4: Functions and Methods
30:What is a dictionary in Python? Explain with a code.
Answer:
Dictionaries in Python store data in key-value pairings. They are unordered and written in curly braces.
dict={
“name”: “Fname”,
“age”: “18”,
“address”: “Kolkata”
}
Print(dict)
31: What is a map() function in Python?
Answer: The map function executes a given function to all iterable items.
32: How do you write comments in Python?
Answer:
Comments are lined developers use to explain a line of code without executing it.
# is used to comment on a line
Example:
num = int(input()) #taking input
Print(num) #printing the value
33: Explain the memory management of Python.
Answer:
- Python Memory Manager is responsible for creating a private memory heap 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.
34: What are new and override modifiers?
Answer:
- New modifiers state that the compiler should run a new function instead of using the one from the base class.
- The 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.
35: What is the use of len()?
Answer: len() calculates the length or the number of elements in a list, array, or string.
36: What does set() do?
Answer: set() converts the iterable element into unique and distinct elements. In other words, set() helps remove duplicate elements from an iterable.
Section 5: Data Structures
37: Differentiate between arrays, lists, and tuples in Python.
Let us return to some technical Python OOPS interview questions. Although they may sound theoretical, simple coding examples will elevate the answers.
Answer:
Differences between list, array, and tuple are:
| List | Array | Tuple |
| 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 indexed | Ordered and indexed | Ordered and indexed |
| Can store one or many data types in a list | It can store the same data type in an array. Mixed data types are not allowed | Can store one or many data types in a list |
| In-built in Python library | Has to be imported | In-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])
38: 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 code that does a module.
- Imagine a single file with data and functions; that is what a 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.
Section 6: Python coding interview questions:
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 and 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 them.
39: Write a code to open a file.
Answer: File_open = open(“samplefile.txt”)
40: Write a code to delete a file.
Answer:
import os
if (os.path.exists(“samplefile.txt”)):
os.remove(“samplefile.txt”)
41: 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)
42: 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)
43: 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()
44: 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
45: What is the difference between range() and xrange()?
Answer:
- range() creates a static list that can be iterated while checking some conditions. This function returns a list with integer sequences.
- xrange() is the same in functionality as range() but it does not return a list, instead it returns an object of xrange(). xrange() is used in yielding generators.
46: What are help() and dir() functions used for?
Answer:
- help() function provides complete information on the modules, classes, and members.
- When help() is called without arguments, it launches an interactive help utility
Below is what the interactive help utility looks like:
dir() function only returns a relevant list of object data 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())
47: What are the different kinds of inheritances supported by Python?
Answer: Python supports four types of inheritance. Those are as follows:
Single inheritance:
When a single child class inherits a single parent 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 child class inherits a parent 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()
48: What are pandas?
Answer:
- Pandas is a name derived from Panel Data, an open-source library for manipulating data.
- Pandas can load data, manipulate data, and analyse and prepare data.
- Pandas is often used for file handling.
49: Is it possible to create an empty class in Python?
Answer: Yes! It is possible. In such instances, the pass keyword is used, which lets the control pass through.
50: How do you 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))
These 50 Python Oops interview questions will help you answer your interviewers and greatly impact 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 of guidelines, you can answer any Python Oops interview questions you are asked.
Conclusion on Python OOPS Interview Questions :
In conclusion, these carefully curated 50 Python OOPS interview questions are a comprehensive resource to help you navigate the intricacies of Object-Oriented Programming in Python.Whether you’re a seasoned developer or a newcomer, mastering these questions will 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 pursuing Python-related career opportunities.
