Python OOPs Interview Questions 2026: 30 Q&A With Code

Last Updated: June 2026 | Level: Freshers to Mid-Level | Read Time: ~16 min

Python's object model is a favourite interview area because it differs subtly from Java and C++. Candidates report that self, class versus instance attributes, dunder methods, and the method resolution order are guaranteed topics for Python developer and data-engineering roles. This guide covers 30 Python OOP questions with full answers and runnable code. Behaviour reflects the official Python data-model documentation; confirm any version-specific detail on the official docs.

Pair this with Python Interview Questions 2026 and Python Data Structures Interview Questions 2026.

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Table of Contents

1. Classes and Instances (Q1 to Q10)
2. Inheritance and MRO (Q11 to Q19)
3. Dunder and Special Methods (Q20 to Q26)
4. Advanced (Q27 to Q30)
5. Predict the Output
6. Quick Revision Table
7. Frequently Asked Questions

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Classes and Instances

Q1. What is the role of self in Python? Easy

class Dog:
    def __init__(self, name):
        self.name = name      # self ties data to this instance
    def bark(self):
        return f"{self.name} says woof"

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Q2. What is the difference between a class attribute and an instance attribute? Medium

class Counter:
    total = 0            # class attribute, shared
    def __init__(self):
        self.id = Counter.total
        Counter.total += 1

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Q3. What is init and is it a constructor? Easy

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Q4. What is the difference between new and init? Hard

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Q5. What are instance, class, and static methods? Medium

class Pizza:
    def __init__(self, size): self.size = size
    @classmethod
    def large(cls): return cls(16)        # alternative constructor
    @staticmethod
    def area(r): return 3.14 * r * r       # utility

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Q6. What is encapsulation in Python? Medium

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Q7. What is name mangling? Hard

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Q8. What are property decorators? Medium

class Account:
    def __init__(self): self._balance = 0
    @property
    def balance(self): return self._balance
    @balance.setter
    def balance(self, v):
        if v >= 0: self._balance = v

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Q9. What does slots do? Hard

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Q10. What is a dataclass? Medium

from dataclasses import dataclass
@dataclass
class Point:
    x: int
    y: int

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Inheritance and MRO

Q11. How does inheritance work in Python? Easy

class Animal:
    def speak(self): return "..."
class Cat(Animal):
    def speak(self): return "meow"

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Q12. What is super() and why use it? Medium

class Base:
    def __init__(self): self.a = 1
class Derived(Base):
    def __init__(self):
        super().__init__()   # run Base setup first
        self.b = 2

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Q13. What is the method resolution order (MRO)? Hard

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Q14. How does Python solve the diamond problem? Hard

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Q15. What is the difference between isinstance and issubclass? Easy

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Q16. What is duck typing? Medium

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Q17. What is an abstract base class? Medium

from abc import ABC, abstractmethod
class Shape(ABC):
    @abstractmethod
    def area(self): ...

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Q18. What is method overriding and does Python have overloading? Medium

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Q19. What is a mixin? Hard

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Dunder and Special Methods

Q20. What is the difference between str and repr? Medium

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Q21. How do you make a class comparable? Medium

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Q22. How do you make an object iterable? Medium

class Range3:
    def __iter__(self):
        for i in range(3): yield i

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Q23. What does call do? Hard

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Q24. How do you support len() and indexing? Medium

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Q25. What is eq and its link to hash? Hard

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Q26. What are context managers and enter/exit? Medium

with open("f.txt") as f:    # __enter__/__exit__ handle close
    data = f.read()

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Advanced

Q27. What is a metaclass? Hard

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Q28. What is the difference between composition and inheritance in Python? Medium

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Q29. Are everything-is-an-object claims true in Python? Medium

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Q30. How does garbage collection work in Python? Hard

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Predict the Output

Snippet 1

class A:
    items = []
    def add(self, x): self.items.append(x)
a, b = A(), A()
a.add(1); b.add(2)
print(a.items)

Output:

[1, 2]

Why: items is a class attribute shared by all instances, so both appends modify the same list. The classic mutable-class-attribute trap. Use self.items = [] in __init__ for per-instance lists.

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Snippet 2

class A:
    def who(self): return "A"
class B(A):
    def who(self): return "B " + super().who()
print(B().who())

Output:

B A

Why: B.who calls super().who() which resolves to A.who via the MRO, concatenating the results.

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Snippet 3

print(type(type))
print(isinstance(5, object))

Output:

<class 'type'>
True

Why: type is its own metaclass, and every value including int derives from object, so 5 is an instance of object.

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Quick Revision Table

Concept	Key takeaway
self	explicit instance reference
class vs instance attr	shared vs per-object
init vs new	initialise vs create
MRO	C3 linearisation, deterministic
super()	delegates to next in MRO
str vs repr	readable vs unambiguous
eq and hash	define together for hashable
mutable class attr	shared, common trap

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Frequently Asked Questions

Which Python OOP topic is asked most in 2026?

Candidates report that the difference between class and instance attributes, the role of self, and the method resolution order for multiple inheritance are the three most repeated Python OOP questions.

Do Python interviews ask about dunder methods?

Yes. __init__, __str__, __repr__, __eq__, and __len__ come up regularly, with interviewers asking you to make a class printable, comparable, or iterable by implementing the right dunder.

Is multiple inheritance asked in Python interviews?

Often, because Python allows it. Interviewers probe the C3 linearisation MRO, the role of super, and the diamond problem, which Python resolves deterministically unlike Java, which bans class multiple inheritance.

Why does a mutable class attribute cause bugs?

Because it is shared across all instances, so appending to a class-level list affects every object. Always initialise mutable per-instance state inside __init__ with self, never as a bare class attribute.

What is the difference between a classmethod and a staticmethod?

A classmethod receives the class as cls and is commonly used for alternative constructors, while a staticmethod receives nothing and is just a function grouped under the class for namespacing.

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Related Articles

• Python Interview Questions 2026, the master set
• Python Data Structures Interview Questions 2026, lists, dicts and more
• Python Output Prediction Questions 2026, tricky snippets
• Java OOPs Interview Questions 2026, compare with Java's model

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Confirm any version-specific behaviour on the official Python documentation before your interview. This guide reflects candidate-reported patterns and public preparation resources as of June 2026.