Top Python OOPS Interview Questions and Answers You Must Know

1. What is Object-Oriented Programming (OOP)?

OOPs is a programming approach that focuses on organizing code into reusable structures called objects. These objects are based on classes, which define the data and behavior of the object.

OOP helps make programs more structured, modular, and reusable by following principles like encapsulation, inheritance, polymorphism, and abstraction. Python is an object-oriented language that makes it easy for programmers to build and work with objects.

2. What are Classes in Python?

A class is like a blueprint or template used to create objects in Python. It defines the properties and actions that the objects will have. Let's take the example of a Car class. Every automobile has unique characteristics, such its brand and model, and it can do things like display its details.

Code Example:

class Car:
    def __init__(self, brand, model):
        # Initializing object attributes
        self.brand = brand  
        self.model = model  

    def display(self):
        # Method to display car details
        print(f"Car: {self.brand} {self.model}")  

# Creating a Car class object (instance)
my_car = Car("Toyota", "Camry")

# Calling the display method
my_car.display()

3. What is an object?

An object is a specific example of a class. It contains both data (attributes) and behaviors (methods) that are part of that class and reflect a real-world entity. For example, if we have a class called Car, we can create multiple objects from it, each representing a different car with unique details like brand and model.

Code Example:

class Car:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def display(self):
        print(f"Car: {self.brand} {self.model}")

# Creating an object of the Car class
car1 = Car("Toyota", "Corolla")
car1.display()  # Output: Car: Toyota Corolla

4. Explain Encapsulation

The theory of encapsulation is to maintain data and the functions that manipulate it together in a single class unit. Additionally, it limits direct access to specific object details by ensuring that data cannot be accidentally altered. Instead of accessing variables directly, special methods are used to retrieve or update values safely.

For example, in a BankAccount class, the balance should not be directly accessed or changed from outside the class to prevent unauthorized modifications. Instead, it is kept private, and controlled methods allow interaction with it.

Code Example:

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance  #Private variables are not directly accessible.

    def get_balance(self):
        """ The balance can be accessed safely using this approach. """
        return self.__balance

5. What is inheritance?

Inheritance is a core focus in object-oriented programming (OOP) that allows one class, known as the child or subclass, to acquire properties and behaviors from another class, known as the parent or superclass. This helps in code reuse, reduces redundancy, and maintains a hierarchical structure in programming. Understanding inheritance is crucial when preparing for Python object oriented programming interview questions, as it is crucial in designing efficient and scalable applications.

For example, you have a general category called Animal, which has a common behavior, speaking. Different animals make different sounds, but all animals can make sounds. Instead of writing the same functionality separately for each type of animal, you can define it in a general class (parent class) and let specific animals (child classes) modify or extend that behavior.

Code Example:

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance  #Private variables are not directly accessible.

    def get_balance(self):
        """ The balance can be accessed safely using this approach. """
        return self.__balance

6. What is Polymorphism?

In object-oriented programming, polymorphism is a notion that permits several classes to perform distinct behavior despite using the same method name. This suggests that, depending on the object calling a method, its implementation may change. Python OOPS Interview Questions use polymorphism to gauge a candidate's understanding of this essential idea.

Consider, for instance, a general class named Animal that has the method speak(). Different animals, like dogs and cats, can have their own versions of speak(), producing different sounds.

Code Example:

class Animal:
    def speak(self):
        return "Some generic animal sound"

class Dog(Animal):
    def speak(self):
        return "Bark"

class Cat(Animal):
    def speak(self):
        return "Meow"

# Using polymorphism
animals = [Dog(), Cat(), Animal()]

for animal in animals:
    print(animal.speak())

‍7. What are instance variables?

Variables that are associated with a particular object (or instance) of a class are known as instance variables. Each object has a separate copy of these variables, meaning changes to one instance do not affect another. Understanding instance variables is important when preparing for Python object oriented interview questions, as it is important in managing object-specific data.

Code Example:

class Student:
    def __init__(self, name):
        self.name = name  # Instance variable

8. What are class variables?

Class variables are attributes that belong to the class itself rather than any specific model. Since they are shared by all instances of the class, any changes made to the class variable by one instance will have an impact on all other instances.

Code Example:

class Employee:
    company = "TechCorp"  
# Creating two instances of Employee
emp1 = Employee()
emp2 = Employee()

print(emp1.company)  # Output: TechCorp
print(emp2.company)  # Output: TechCorp

# Modifying the class variable
Employee.company = "NewCorp"

print(emp1.company)  # Output: NewCorp
print(emp2.company)  # Output: NewCorp

9. Explain the __init__ method. 

When a class object is formed in Python, the __init__ method is immediately called, acting as a constructor. It mostly establishes the object's initial state by giving its attributes values, either the default values or the values supplied at instantiation.

How It Works:

• The __init__ method is a special function in a class, defined using def __init__(self, ...), where self indicates the current version of the class.
• It allows passing arguments to set up the object with specific values when it is created.
• Without an __init__ method, an object can still be created, but it won't have any initial values assigned unless done manually.

Code Example:

class Car:
    def __init__(self, brand, model, year):
        self.brand = brand
        self.model = model
        self.year = year

# Creating an object of the Car class
my_car = Car("Toyota", "Corolla", 2022)

# Accessing attributes
print(my_car.brand)  # Output: Toyota
print(my_car.model)  # Output: Corolla
print(my_car.year)   # Output: 2022

10. How do you create an instance of a class?

In Python, you must call a class with its name enclosed in parenthesis in order to make an instance of it. Using the class blueprint as a guide, this procedure initializes a new object.

Code Example:

class Car:  
    def __init__(self, brand, model):  
        self.brand = brand  
        self.model = model  

# Creating an instance of the Car class  
my_car = Car("Toyota", "Corolla")  

Note:

The secret to answering Python OOPS interview questions is to grasp these fundamental ideas. They offer a strong foundation for understanding real-world applications. To get better, concentrate on examples, clarity, and regular practice.

At the intermediate level, interviewers often evaluate how well you apply OOP concepts in real-world scenarios rather than just defining them. These Python coding questions for interview usually focus on classes, inheritance, polymorphism, and writing clean, reusable code.

11. What is Method Overriding?

Method overriding is when a subclass changes a method that its parent class already has. The method name and parameters remain unchanged, so the child class can have different behavior.

In the context of Python object-oriented programming interview questions, method overriding is a commonly discussed topic, as it shows polymorphism and how subclasses can customize inherited methods.

In Python, method overriding happens when a subclass defines a method with the same name and parameters as a method in its superclass. The version from the child class is used rather than the parent when an object of the subclass invokes the overridden method. This is useful for modifying or extending the functionality of inherited methods without changing the parent class.

Code Example:

class Animal:
    def speak(self):
        return "Some generic sound"

class Dog(Animal):
    def speak(self):
        return "Bark"

dog = Dog()
print(dog.speak())  # Output: Bark

12. How does Python support multiple inheritance?

Inheritance, especially multiple inheritance, which permits a class to inherit from more than one parent class, is often addressed in Python OOPS interview questions. This means a child class can access attributes and methods from multiple parent classes. To achieve this, you simply list the parent classes in parentheses, separated by commas, when defining the child class.

Code Example:

class Parent1:
    def method1(self):
        return "Method from Parent1"

class Parent2:
    def method2(self):
        return "Method from Parent2"

class Child(Parent1, Parent2):
    pass

obj = Child()
print(obj.method1())  # Output: Method from Parent1
print(obj.method2())  # Output: Method from Parent2

13. What is the use of the self keyword?

Within a class, the current instance of the class is referred to using the self keyword. It makes instance variables and methods accessible. Python wouldn't know which object's data to operate with without self. In order to differentiate between instance characteristics and local variables, it is essential to comprehend the role of the self.

Code Example:

class Car:
    def __init__(self, brand):
        self.brand = brand  # self.brand refers to the instance variable

    def show_brand(self):
        return f"The car brand is {self.brand}"

my_car = Car("Toyota")
print(my_car.show_brand())  # Output: The car brand is Toyota

14. What are decorators in Python?

Functions known as decorators change how other functions or methods behave without changing their underlying code. They are used to add functionality like logging, authentication, or timing execution.

Code Example:

def decorator_function(original_function):
    def wrapper():
        print("Function is being called...")
        original_function()
        print("Function execution completed.")
    return wrapper

@decorator_function
def say_hello():
    print("Hello!")

say_hello()

Output:

Function is being called...
Hello!
Function execution completed.

15. How can you implement abstraction in Python?

Abstraction is achieved by using abstract base classes (ABCs) from the abc module. An abstract class defines methods that must be implemented by its subclasses.

Code Example:

from abc import ABC, abstractmethod

class Animal(ABC):
    @abstractmethod
    def make_sound(self):
        pass  # This method must be implemented in child classes

class Dog(Animal):
    def make_sound(self):
        return "Bark"

class Cat(Animal):
    def make_sound(self):
        return "Meow"

dog = Dog()
cat = Cat()
print(dog.make_sound())  # Output: Bark
print(cat.make_sound())  # Output: Meow

16. What is operator overloading?

By using operator overloading, you can specify how operators (such as +, -, *, etc.) interact with your classes' objects.

Code Example:

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Point(self.x + other.x, self.y + other.y)

p1 = Point(2, 3)
p2 = Point(4, 5)
result = p1 + p2
print(result.x, result.y)  # Output: 6 8

17. Difference between public, protected, and private attributes

• Public (var): Accessible from any location. 
• Protected (_var): Only members of the class and its subclasses should be able to access protected (_var). 
• Private (__var): Cannot be accessed directly outside the class.

Code Example:

class Example:
    def __init__(self):
        self.public = "I am public"
        self._protected = "I am protected"
        self.__private = "I am private"

obj = Example()
print(obj.public)      # Allowed
print(obj._protected)  # Allowed (but should be used carefully)
print(obj.__private)   # Error: AttributeError

18. What are mixins in Python?

Special classes called mixins are used to include reusable methods into other classes without joining the main inheritance structure. Without imposing a rigid parent-child connection, they provide modular functioning. Examining Python object-oriented interview questions might help you better grasp ideas like mixins, multiple inheritance, and design patterns if you're getting ready for a technical talk.

Code Example:

class LoggingMixin:
    def log(self, message):
        print(f"LOG: {message}")

class User(LoggingMixin):
    def __init__(self, name):
        self.name = name

    def greet(self):
        self.log(f"{self.name} says hello!")  # Using mixin method

user = User("Alice")
user.greet()  # Output: LOG: Alice says hello!

19. How do you define static methods in Python?

Instead of being connected to any specific object, a static method is connected to the class itself. It is defined using @staticmethod and does not need self.

Code Example:

class MathUtils:
    @staticmethod
    def add(x, y):
        return x + y

print(MathUtils.add(5, 10))  # Output: 15

20. What is method chaining?

Method chaining allows multiple methods to be called on the same object in a single statement, making the code more concise.

Code Example:

class TextProcessor:
    def __init__(self, text):
        self.text = text

    def to_upper(self):
        self.text = self.text.upper()
        return self

    def remove_spaces(self):
        self.text = self.text.replace(" ", "")
        return self

    def show(self):
        print(self.text)
        return self

TextProcessor("Hello World").to_upper().remove_spaces().show()

Output:

HELLO WORLD

Note:

Mastering these intermediate-level Python OOPs interview questions deepens your grasp of real-world OOP applications. They reveal how Python handles core principles like abstraction, method overriding, and mixins effectively. Prepare with examples and real scenarios to confidently tackle OOP-based Python interviews.

21. How can polymorphism help create different report formats?

You may design a common interface for several report kinds thanks to polymorphism. You may develop subclasses like PDFReport and HTMLReport after creating a base class called Report with a method like generate_report(). Generate_report() is implemented by each subclass in a way that produces the report in its own format. This makes it possible to introduce new report formats without changing the code that already exists.

22. How do you implement a context manager using a class?

A context manager in Python helps manage resources like file handling or database connections efficiently. It can be implemented using a class by defining the __enter__() and __exit__() methods. The __enter__() method sets up the resource, while __exit__() ensures proper cleanup. This allows the use of the with statement for automatic resource management.

23. How would you design a library management system using OOP?

Classes like Book, Member, and Transaction can be used to develop a library management system. Relevant attributes would be contained in each class (e.g., title, author for Book; name, membership_id for Member). While methods like borrow_book() and return_book() handle essential functions, inheritance may be utilized for many kinds of books or users.

24. How can OOP help with API versioning?

API versioning is made simpler by OOP concepts like abstraction and encapsulation. Creating distinct API class versions (e.g., APIv1, APIv2) with their methods while maintaining a similar interface is one strategy. Smooth version transitions are ensured via a factory design that can dynamically create the appropriate version based on user requests.

25. What are the best practices for error handling in OOP?

Using exceptions is a key component of effective OOP error handling. Create unique exception classes for particular application issues (e.g., InvalidInputError, DatabaseConnectionError) in place of general errors. Debugging is improved and crashes are avoided when exceptions are caught and handled at the proper levels.

Note: When preparing for Python object oriented programming interview questions, learning how to implement structured error handling with custom exceptions can indicate strong OOP principles.

26. What are abstract base classes (ABCs), and when should you use them?

Python's abstract base classes, or ABCs, serve as a model for other classes. They include abstract methods that subclasses are required to implement. ABCs ensure a consistent interface across multiple implementations. Use them when you want to enforce method definitions without providing actual implementations.

27. How would you design a plugin system using OOP?

A plugin system can be implemented using interfaces or abstract classes. The base Plugin class can define methods that all plugins must implement. Specific plugins can then inherit from this class and provide functionality. Plugins can be loaded dynamically at runtime using Python’s importlib module, making the system flexible and extensible.

28. How do you decide between using inheritance and composition in Python?

• Inheritance: Inheritance is used when there is a logical "is-a" relationship between classes — for instance, a Car can be considered a type of Vehicle.
• Composition: It is used when one class contains another as a component (e.g., a Car class having an Engine object).

When components may alter independently, composition is preferred because it offers greater flexibility and avoids complicated inheritance hierarchies.

29. What are descriptors in Python?

You can determine how attributes are accessible within a class by using descriptors. They make use of unique functions like set(), delete(), and get(). In frameworks like Django, descriptors are frequently used to manage model fields and dynamically enforce validation criteria. Given their importance in attribute management and customisation, descriptors must be understood in order to answer sophisticated Python object-oriented interview questions.

30. How can you dynamically load classes based on user input?

Applications are more adaptable when dynamic class loading is used. It can be done using:

• getattr(): Uses a string input to retrieve a class or function from a module.
• importlib.import_module(): Loads a module dynamically at runtime.

31. What is the method resolution order (MRO), and how can it affect operator overloading in multiple inheritance scenarios?

The method resolution order (MRO) determines the order in which Python looks for methods (including special methods like __add__) in a class hierarchy when multiple inheritance is used. If multiple parent classes implement __add__, Python uses the MRO (calculated using the C3 linearization algorithm) to decide which implementation to use. In complicated inheritance hierarchies, this guarantees predictable and consistent operator behavior.

32. Can you overload other operators besides + in Python? Provide an example with a different operator.

Yes, you may define the equivalent custom methods for many operators in Python to overload them. For instance, you use __mul__ to overload the * operator. 

Example:

class Scalar:
    def init(self, value):
        self.value = value

    def __mul__(self, other):
        return Scalar(self.value * other.value)

a = Scalar(2)
b = Scalar(5)

result = a * b  # Uses mul
print(result.value)  # Output: 10

1. Explain concepts without using technical jargon
   Interviewers value clarity. Practice explaining OOP ideas like inheritance or polymorphism in plain language, as if teaching a beginner.
2. Know why OOP is not the best choice sometimes
   Being able to say when OOP is unnecessary, or when a simple function-based approach works better, shows mature problem-solving skills.
3. Understand Python’s behavior, not just definitions
   Learn how Python actually handles things like object references, mutable vs immutable objects, and method resolution order (MRO).
4. Be comfortable reading unfamiliar code
   Instead of coding from scratch, interviews frequently include examining or troubleshooting code. Practice rapidly comprehending the OOP code of others.
5. Link OOP concepts to performance and maintainability
   Prepare an explanation of how OOP design enhances not just accuracy but also code reuse, testing, and long-term maintenance.

It's important to fully comprehend object-oriented programming ideas in order to respond appropriately to Python OOPs interview questions. You may efficiently prepare with the aid of these questions, which range in difficulty from beginner to intermediate. In order to successfully respond to questions about Python OOP and inheritance in your interview, practice developing code examples and concentrate on understanding the fundamental concepts.