Top 40 Python interview questions and answers

Here’s a comprehensive list of Python interview questions along with brief answers. These questions are categorized for ease of study, covering beginner to advanced topics:

Python interview questions and answers

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1. Python Basics

1. What is Python?
   • Python is a high-level, interpreted, and dynamically typed programming language known for its simplicity and readability. It’s widely used for web development, data analysis, AI/ML, and more.
2. What are Python’s key features?
   • Easy to learn, dynamic typing, interpreted, cross-platform, extensive libraries, object-oriented, and supports multiple programming paradigms.
3. What are Python’s data types?
   • Common data types include int, float, str, list, tuple, dict, set, and bool.
4. What are Python’s reserved keywords?
   • Examples include if, else, while, for, True, False, None, try, except, class, def, etc.
5. What is PEP 8?
   • PEP 8 is Python’s style guide for writing clean and readable code.

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2. Data Structures in Python interview questions and answers

6. What is the difference between a list and a tuple?
   • Lists are mutable, while tuples are immutable. Tuples are faster than lists for iteration.
7. How does a set differ from a list?
   • A set is an unordered collection of unique elements, while a list is ordered and allows duplicates.
8. What is a dictionary in Python?
   • A dictionary is an unordered collection of key-value pairs, where keys are unique.
9. What are list comprehensions?
   • A concise way to create lists. Example: [x**2 for x in range(5)] creates [0, 1, 4, 9, 16].
10. How do you sort a list in Python?

• Use list.sort() for in-place sorting or sorted(list) to return a new sorted list.

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3. Python Functions Python interview questions and answers

11. What are Python’s built-in functions?

• Common ones include len(), range(), print(), type(), max(), min(), sum(), sorted(), and input().

12. What is the difference between *args and **kwargs?

• *args passes a variable number of positional arguments, while **kwargs passes a variable number of keyword arguments.

13. What is a lambda function?

• A small anonymous function defined using the lambda keyword. Example: add = lambda x, y: x + y.

14. What is the purpose of decorators in Python?

• Decorators modify the behavior of a function or class without changing its code. Example:

def decorator(func):
    def wrapper():
        print("Before function")
        func()
        print("After function")
    return wrapper
@decorator
def hello():
    print("Hello!")
hello()

15. What are Python’s function annotations?

• They provide optional metadata about function parameters and return values. Example:

def add(a: int, b: int) -> int:
    return a + b

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4. Python OOP (Object-Oriented Programming)

16. What are the principles of OOP?

• Encapsulation, Abstraction, Inheritance, and Polymorphism.

17. How is inheritance implemented in Python?

• By passing the parent class as an argument to the child class. Example:

class Parent:
    pass
class Child(Parent):
    pass

18. What are __init__ and self in Python classes?

• __init__ is the constructor method, and self refers to the instance of the class.

19. What are magic methods?

• Special methods surrounded by double underscores (e.g., __str__, __repr__, __add__), used to override default behaviors.

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

• is checks for object identity, while == checks for value equality.

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5. Advanced Python

21. What are Python generators?

• Generators are functions that yield values one at a time using yield. They are memory-efficient.

22. What is the Global Interpreter Lock (GIL)?

• A mutex in CPython that allows only one thread to execute Python bytecode at a time, limiting true multithreading.

23. What are metaclasses in Python?

• Metaclasses define the behavior of classes themselves. They control class creation.

24. Explain Python’s garbage collection mechanism.

• Python uses reference counting and a cyclic garbage collector to manage memory.

25. What are Python’s built-in modules for threading?

• The threading module for threads and the multiprocessing module for parallel processes.

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6. File Handling In Python interview questions and answers

26. How do you open a file in Python?

• Using the open() function. Example:

with open('file.txt', 'r') as f:
    content = f.read()

27. What modes can you use to open a file?

• 'r' (read), 'w' (write), 'a' (append), 'rb' (read binary), etc.

28. How do you handle exceptions during file operations?

• Use a try...except block. Example:

try:
    with open('file.txt', 'r') as f:
        print(f.read())
except FileNotFoundError:
    print("File not found.")

29. How do you write to a file?

• Use the 'w' or 'a' mode with the write() method:

with open('file.txt', 'w') as f:
    f.write("Hello, world!")

30. What is the difference between read() and readlines()?

• read() reads the entire file as a string, while readlines() returns a list of lines.

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7. Python Libraries Python interview questions

31. What is the difference between NumPy and Pandas?

• NumPy is used for numerical computations, while Pandas is used for data manipulation and analysis.

32. What is Flask/Django, and when would you use them?

• Flask is a lightweight web framework for smaller projects. Django is a full-stack framework for larger, more complex projects.

33. How do you handle HTTP requests in Python?

• Using the requests library for client-side requests and frameworks like Flask/Django for server-side requests.

34. What is the purpose of the os and sys modules?

• The os module interacts with the operating system, and sys provides access to Python runtime environment variables and system functions.

35. What is the difference between pip and conda?

• pip installs Python packages, while conda manages packages and environments for Python and other languages.

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8. Python Debugging and Testing

36. What tools do you use for debugging Python code?

• Tools like pdb, ipdb, logging modules, and IDE debuggers (e.g., in PyCharm or VSCode).

37. What is the difference between unit testing and integration testing?

• Unit testing tests individual components, while integration testing ensures different components work together.

38. What is the unittest module in Python?

• A built-in module for writing and running tests.

39. How do you handle exceptions in Python?

• Using try...except blocks. You can add finally for cleanup and else for code to run if no exception occurs.

40. What are assertions in Python?

• Assertions are statements that test assumptions in code. Example:

assert 2 + 2 == 4, "Math is broken!"

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Tips for Preparation – Python interview questions

• Practice coding problems on platforms like LeetCode or HackerRank.
• Study Python’s official documentation for in-depth knowledge.
• Review projects you’ve worked on to answer real-world scenario questions confidently.

Let me know if you’d like detailed explanations or examples for specific questions! basic python interview questions

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