The Best Python Interview Questions and Answers (2025 Guide)

Preparing for a Python interview requires more than just knowing the syntax; it demands a solid understanding of the language’s core principles. This comprehensive guide provides answers to the most frequently asked Python interview questions, helping you build a strong foundation and demonstrate your expertise with confidence.

Let’s dive into the questions that will help you ace your next Python interview.

Python Fundamentals & Core Concepts

1. What is Python?

Python is a high-level, interpreted, dynamically typed, and general-purpose programming language. Created by Guido van Rossum and first released in 1991, it is famous for its simple, readable syntax, which emphasizes code clarity and reduces development time. Python supports multiple programming paradigms, including object-oriented, imperative, and functional programming.

2. What are Python’s key features?

Interviewers often ask about Python’s standout features to gauge your overall knowledge. Key features include:

Easy to Learn and Read: Python’s syntax is designed to be clean and simple, making it accessible for beginners.
Dynamically Typed: You don’t need to declare the data type of a variable, as Python determines it at runtime.
Interpreted: Python code is executed line by line, which makes debugging easier.
Vast Standard Library: Python comes with a massive library of modules for a wide range of tasks, from web development to data science.
Cross-Platform: Python code can run on various operating systems, including Windows, macOS, and Linux.

3. What is PEP 8?

PEP 8 is the official style guide for writing Python code. It stands for Python Enhancement Proposal 8. It provides a set of conventions for code layout, naming conventions, and best practices to ensure code is clean, readable, and consistent across the Python community. Following PEP 8 is a sign of good practice. You can find the full guide in the official PEP 8 documentation.

4. How is Python an interpreted language?

Python is considered an interpreted language because the Python interpreter executes the code directly. When a Python script is run, the interpreter first compiles the source code into an intermediate format called bytecode. This bytecode is then executed by the Python Virtual Machine (PVM), which makes Python code portable across different platforms without needing to recompile.

5. What is the difference between `is` and `==`?

This is a classic question to test your knowledge of object identity:

== (double equals) is a comparison operator that checks if the values of two objects are equal.
is is an identity operator that checks if two variables refer to the exact same object in memory.

Python

a = [1, 2, 3]
b = [1, 2, 3]
c = a

print(a == b)  # Output: True (values are equal)
print(a is b)  # Output: False (they are different objects)
print(a is c)  # Output: True (they refer to the same object)

Python Data Structures & Types

6. What are Python’s built-in data types?

Python’s core data types are essential to know. They include:

Numeric Types: int, float, complex
Sequence Types: str, list, tuple, range
Mapping Type: dict
Set Types: set, frozenset
Boolean: bool (True and False)
NoneType: None

Python

int, float, str, list, tuple, dict, set, bool, NoneType

int, float, str, list, tuple, dict, set, bool, NoneType

For a deeper dive, the official Python documentation on Built-in Types is an excellent resource.

7. What is the difference between a list and a tuple?

This is one of the most common Python interview questions for beginners. Both are ordered collections of items, but they differ in mutability:

Lists are mutable, meaning you can add, remove, or modify elements after the list has been created. They are defined using square brackets: [1, 2, 'a'].
Tuples are immutable, meaning their elements cannot be changed once the tuple is created. They are defined using parentheses: (1, 2, 'a').

8. What is a dictionary in Python?

A dictionary is an unordered collection of key-value pairs. Dictionaries are optimized for retrieving values when the key is known. Keys must be unique and immutable, while values can be of any data type.

9. What is the difference between `append()` and `extend()`?

Both methods are used to add elements to a list:

append() adds a single element to the end of a list. This element can be another list, making it a nested list.
extend() iterates over an iterable (like another list, tuple, or string) and adds each element of that iterable to the end of the original list.

Object-Oriented Programming (OOP) in Python

10. What is a class?

A class is a blueprint or a template for creating objects. It defines a set of attributes (data) and methods (functions) that the objects created from it will have.

11. What is the `self` keyword used for?

In a class, self is a reference to the instance of the class. It is the first parameter of every method inside a class. When a method is called on an object, self gives you access to the object’s attributes and methods.

12. Explain the `init` method.

The __init__ method is a special method in Python classes, known as the constructor. It is automatically called when a new instance of a class is created. Its purpose is to initialize the attributes of the new object.

Functions & Control Flow

13. How do you define a function in Python?

You define a function using the def keyword, followed by the function name, parentheses (), and a colon :. The function body is indented below.

Python

def greet(): print("Hello")

def greet(): print("Hello")

14. What is a `lambda` function?

A lambda function is a small, anonymous function defined with a single expression. They are typically used for a short period and are great for functional programming tasks, such as being passed as an argument to a higher-order function like map(), filter(), or sorted().

Python

square = lambda x: x*x

square = lambda x: x*x

15. What are `*args` and `**kwargs`?

These are used to pass a variable number of arguments to a function:

*args allows a function to accept a variable number of positional arguments. It collects these arguments into a tuple.
**kwargs allows a function to accept a variable number of keyword arguments. It collects these arguments into a dictionary.

Python

 *args: variable positional args
 **kwargs: variable keyword args

 *args: variable positional args
 **kwargs: variable keyword args

16. What is a decorator?

A decorator is a design pattern in Python that allows you to wrap another function to extend or modify its behavior without permanently altering the function itself. Decorators are defined using the @ symbol before a function definition.

17. What is a generator?

A generator is a function that returns an iterator. It uses the yield keyword instead of return to produce a sequence of values one at a time. Generators are memory-efficient, as they generate values on the fly rather than storing them all in memory at once.

18. What is recursion?

Recursion is a programming technique where a function calls itself to solve a problem. It must have a base case—a condition that stops the recursion—to prevent an infinite loop.

Additional Python Interview Questions

Here are a few more advanced topics that are great to know for your interview:

19. What is a Python virtual environment?

A virtual environment is an isolated Python environment that allows you to manage dependencies for a specific project without affecting other projects or the global Python installation.

20. What is the Python GIL (Global Interpreter Lock)?

The GIL is a mutex (or a lock) that protects access to Python objects, preventing multiple native threads from executing Python bytecode at the same time. While it makes a single-threaded program run faster, it can be a bottleneck for CPU-bound multi-threaded programs. For more information, you can read about the GIL on Wikipedia.

By thoroughly reviewing these Python interview questions, you will be well-prepared to demonstrate a comprehensive understanding of the language. Good luck!

This article is part of our Interview Prep series.

Introduction

Python Fundamentals & Core Concepts

1. What is Python?

2. What are Python’s key features?

3. What is PEP 8?

4. How is Python an interpreted language?

5. What is the difference between is and ==?

Python Data Structures & Types

6. What are Python’s built-in data types?

7. What is the difference between a list and a tuple?

8. What is a dictionary in Python?

9. What is the difference between append() and extend()?

Object-Oriented Programming (OOP) in Python

10. What is a class?

11. What is the self keyword used for?

12. Explain the __init__ method.

Functions & Control Flow

13. How do you define a function in Python?

14. What is a lambda function?

15. What are *args and **kwargs?

16. What is a decorator?

17. What is a generator?

18. What is recursion?

Additional Python Interview Questions

19. What is a Python virtual environment?

20. What is the Python GIL (Global Interpreter Lock)?

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5. What is the difference between `is` and `==`?

9. What is the difference between `append()` and `extend()`?

11. What is the `self` keyword used for?

12. Explain the `init` method.

14. What is a `lambda` function?

15. What are `*args` and `**kwargs`?