Top 50 Python Interview Questions (2026)
OOP, decorators, generators, GIL, data structures and more — everything you need for your Python interview.
Interview Questions & Answers
What is Python?
Python is a high-level, interpreted, general-purpose programming language. Known for its simple, readable syntax. Supports multiple programming paradigms: procedural, object-oriented, and functional. Used in web dev, data science, AI/ML, automation.
What is the difference between a list and a tuple?
Lists are mutable (can be changed) and use square brackets []. Tuples are immutable (cannot be changed) and use parentheses (). Tuples are faster and used for fixed data. Lists are for collections that change.
What are Python decorators?
A decorator is a function that takes another function and extends its behavior without modifying it. Uses @syntax. Common examples: @staticmethod, @classmethod, @property, @login_required in Django.
What is a generator in Python?
A generator is a function that yields values one at a time using the yield keyword instead of return. It is memory efficient for large data sets because it produces items only when needed, not all at once.
What is the difference between deep copy and shallow copy?
Shallow copy creates a new object but references the same nested objects (copy.copy()). Deep copy creates a completely independent clone including nested objects (copy.deepcopy()). Modifying nested objects in shallow copy affects the original.
What is *args and **kwargs?
*args allows passing a variable number of positional arguments to a function as a tuple. **kwargs allows passing a variable number of keyword arguments as a dictionary. Useful for flexible function signatures.
What are list comprehensions?
List comprehensions provide a concise way to create lists. Syntax: [expression for item in iterable if condition]. Example: [x*2 for x in range(10) if x%2==0]. Faster and more Pythonic than for loops.
What is the GIL (Global Interpreter Lock)?
The GIL is a mutex that protects access to Python objects, preventing multiple threads from executing Python bytecode simultaneously. It limits true parallelism in CPU-bound tasks. Use multiprocessing for CPU-bound, threading for I/O-bound tasks.
What is the difference between is and ==?
== checks value equality (do they have the same value?). is checks identity equality (are they the same object in memory?). Example: a = [1,2]; b = [1,2]; a==b is True but a is b is False.
What are Python data types?
Built-in types: int, float, complex (numbers), str (string), bool, list, tuple, dict, set, frozenset, None. Everything in Python is an object.
What is OOP in Python?
Object-Oriented Programming in Python uses classes and objects. Four pillars: Encapsulation (bundling data and methods), Inheritance (child class inherits from parent), Polymorphism (same interface, different behavior), Abstraction (hiding implementation).
What is the difference between @staticmethod and @classmethod?
@staticmethod does not receive any implicit first argument — it's just a regular function inside a class. @classmethod receives the class (cls) as first argument and can access/modify class state.
What are lambda functions?
Lambda functions are anonymous, single-expression functions. Syntax: lambda arguments: expression. Example: square = lambda x: x**2. Used in map(), filter(), sorted() as short, throwaway functions.
What is exception handling in Python?
Use try/except/finally blocks. try contains code that might fail. except catches specific exceptions. else runs if no exception occurred. finally always runs. Raise custom exceptions by inheriting from Exception class.
What is a Python dictionary?
A dictionary is an unordered (ordered in Python 3.7+) collection of key-value pairs. Keys must be unique and immutable. Operations: dict[key] to access, dict.get(key) for safe access, dict.items() to iterate.
What is __init__ in Python?
__init__ is the constructor method in Python classes. It is called automatically when a new instance is created. Used to initialize the object's attributes. self refers to the current instance.
What is the difference between mutable and immutable objects?
Mutable objects can be changed after creation: list, dict, set. Immutable objects cannot be changed: int, float, str, tuple, frozenset. Immutable objects are hashable and can be used as dictionary keys.
What is map() and filter()?
map(function, iterable) applies a function to every item in an iterable and returns a map object. filter(function, iterable) filters items where function returns True. Both are lazy — use list() to evaluate.
What is PEP 8?
PEP 8 is the style guide for Python code. Key rules: 4 spaces for indentation, max 79 characters per line, two blank lines between top-level functions/classes, one blank line between methods, lowercase with underscores for variable names.
What are Python modules and packages?
A module is a single .py file containing Python code. A package is a directory containing multiple modules and an __init__.py file. Use import to access them. Example: import os, from datetime import datetime.
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