75+ Python Interview Questions and Answers in 2024

1. What is Python?
   • Answer: Python is an interpreted, high-level, general-purpose programming language known for its readable syntax and dynamic typing. It supports various programming paradigms, including procedural, object-oriented, and functional programming.
2. What are the key features of Python?
   • Answer: Key features include easy syntax, interpreted language, dynamically typed, extensive standard library, supports multiple paradigms, cross-platform, and has a large community.
3. What is PEP 8?
   • Answer: PEP 8 is a style guide that provides coding conventions for Python code to improve readability and consistency.
4. What are Python decorators?
   • Answer: Decorators are special functions that modify the behavior of another function or method without changing its actual code.
5. Explain the difference between list and tuple.
   • Answer: Lists are mutable, and tuples are immutable. Lists use square brackets [], and tuples use parentheses ().
6. What is the difference between append() and extend() methods in lists?
   • Answer: append() adds a single element, while extend() adds multiple elements from an iterable.
7. How is memory managed in Python?
   • Answer: Python manages memory using a private heap and garbage collection to clean up unreferenced objects.
8. What is a Python lambda function?
   • Answer: A lambda function is an anonymous, single-expression function defined with the lambda keyword.
9. What is the purpose of the self keyword?
   • Answer: self refers to the current instance of a class and allows access to its methods and attributes.
10. Explain the use of the with statement in Python.
    • Answer: The with statement manages resources like file handling by automatically closing the resource after use.
11. What are Python modules and packages?
    • Answer: Modules are single Python files, while packages are directories containing multiple modules and an __init__.py file.
12. What is list comprehension?
    • Answer: List comprehension provides a concise way to create lists in a single line of code.
13. What is a Python iterator?
    • Answer: An iterator is an object that allows traversing through all elements of a collection one at a time using next().
14. What is the difference between == and is in Python?
    • Answer: == checks for value equality, while is checks for identity (whether two references point to the same object).
15. Explain the __init__ method in Python.
    • Answer: __init__ is a constructor method that initializes an object’s state when it is created.
16. What are Python magic methods?
    • Answer: Magic methods (or dunder methods) are special methods like __init__, __str__, and __len__ that enable operator overloading and other behaviors.
17. How do you handle exceptions in Python?
    • Answer: Exceptions are handled using try, except, finally, and else blocks.
18. What is the purpose of the finally block?
    • Answer: The finally block executes code regardless of whether an exception is raised, commonly used for cleanup tasks.
19. What is the difference between break, continue, and pass statements?
    • Answer:
      • break: Terminates the nearest loop.
      • continue: Skips the current iteration and continues with the next.
      • pass: Does nothing; it’s a placeholder.
20. Explain Python’s @staticmethod and @classmethod decorators.
    • Answer:
      • @staticmethod: Defines a method without access to the class instance or state.
      • @classmethod: Defines a method that accesses the class state via cls.
21. What is the Global Interpreter Lock (GIL)?
    • Answer: The GIL is a mutex that prevents multiple native threads from executing Python bytecodes simultaneously.
22. How can you achieve multithreading in Python?
    • Answer: Use the threading module, but true parallelism is limited due to the GIL. Use multiprocessing for parallelism.
23. What is the difference between deepcopy and copy?
    • Answer:
      • copy: Creates a shallow copy of an object.
      • deepcopy: Creates a deep copy, duplicating all objects recursively.
24. What are Python metaclasses?
    • Answer: A metaclass is the class of a class, defining how classes behave.
25. What is the difference between range() and xrange()?
    • Answer:
      • range(): Generates a list (Python 3.x).
      • xrange(): Generates an iterator (Python 2.x).
26. What is monkey patching in Python?
    • Answer: Monkey patching is dynamically modifying a module or class at runtime.
27. What is the yield keyword?
    • Answer: yield is used in a function to make it a generator, returning values one at a time and saving the function’s state.
28. What are Python generators?
    • Answer: Generators are functions that yield values one at a time, preserving function state between calls.
29. Explain the difference between multiprocessing and multithreading.
    • Answer:
      • Multiprocessing uses separate processes, achieving true parallelism.
      • Multithreading uses threads within a single process, limited by the GIL.
30. What is __slots__?
    • Answer: __slots__ limits the attributes of a class, saving memory by not creating a __dict__ for each instance.
31. What are Python data structures?
    • Answer: Python data structures include lists, dictionaries, sets, tuples, and abstract data types like stacks and queues.
32. How does the set data structure work?
    • Answer: A set is an unordered collection of unique elements supporting set operations like union, intersection, and difference.
33. Explain the difference between dict and OrderedDict.
    • Answer:
      • dict: Does not maintain order in Python versions before 3.7.
      • OrderedDict: Maintains insertion order.
34. How is a deque different from a list?
    • Answer: A deque supports fast appends and pops from both ends, unlike lists, which are slower at the start.
35. What are namedtuples in Python?
    • Answer: namedtuple is a tuple subclass that provides named fields for better readability.
36. Explain how to use Python’s heapq module.
    • Answer: The heapq module provides heap queue algorithms for implementing min-heaps.
37. What is the difference between arrays and lists in Python?
    • Answer: Arrays require homogeneous elements, while lists can hold elements of any type.
38. How can you remove duplicates from a list?
    • Answer: Use set() or list comprehensions like list(dict.fromkeys(list)) to remove duplicates.
39. What is a Python heap?
    • Answer: A heap is a specialized tree-based data structure that satisfies the heap property, where each parent node is ordered according to a specific order.
40. Explain how you can reverse a string in Python.
    • Answer: Use slicing: string[::-1] or the reversed() function.
41. What is the pass statement in Python?
    • Answer: pass is a null operation used as a placeholder when no action is required.
42. How can you swap two variables in Python?
    • Answer: Use tuple unpacking: a, b = b, a.
43. Explain how to handle missing keys in a dictionary.
    • Answer: Use dict.get(key) to return None instead of raising a KeyError.
44. What is the defaultdict class?
    • Answer: defaultdict is a subclass of dict that provides a default value for missing keys.
45. What is the Counter class in Python?
    • Answer: Counter is a subclass of dict for counting hashable objects.
46. How can you sort a list in Python?
    • Answer: Use list.sort() for in-place sorting or sorted() for a new sorted list.
47. What is the purpose of the enumerate() function?
    • Answer: enumerate() adds a counter to an iterable, returning index-value pairs.
48. How do you read and write files in Python?
    • Answer: Use open() with modes like 'r', 'w', or 'a' for reading, writing, or appending.
49. What are Python docstrings?
    • Answer: Docstrings are string literals used to document modules, classes, methods, and functions.
50. How do you convert data types in Python?
    • Answer: Use functions like int(), str(), float(), and list() for type conversion.

Advanced Python Interview Questions

51. What is the property() function?
    • Answer: property() is used to manage class attributes with getter, setter, and deleter methods.
52. Explain Python’s map() function.
    • Answer: map() applies a given function to each item in an iterable, returning a map object.
53. What is the difference between filter() and map()?
    • Answer: filter() returns items from an iterable that satisfy a condition, while map() applies a function to all items.
54. How does the zip() function work?
    • Answer: zip() combines elements from multiple iterables into tuples.
55. What are Python descriptors?
    • Answer: Descriptors are objects that define how attribute access is managed through __get__(), __set__(), and __delete__() methods.
56. What is monkey patching in Python?
    • Answer: Dynamically modifying a class or module at runtime.
57. How to perform unit testing in Python?
    • Answer: Use the unittest module to define and run tests.
58. What are Python coroutines?
    • Answer: Coroutines are functions that can pause and resume execution using await, primarily used for asynchronous programming.
59. Explain how you can make a script executable.
    • Answer: Add #!/usr/bin/env python3 at the top and give execute permissions using chmod +x.
60. What is Python’s Global Interpreter Lock (GIL)?
    • Answer: GIL is a mutex that restricts execution to one thread at a time, limiting multithreading performance.
61. Explain what __name__ == "__main__" means.
    • Answer: It checks if the script is run directly or imported as a module.
62. What is the collections module?
    • Answer: The collections module offers specialized data structures like deque, Counter, and OrderedDict.
63. How do you implement singleton classes in Python?
    • Answer: Use the __new__() method or decorators to ensure only one instance.
64. What are context managers in Python?
    • Answer: Context managers manage resource allocation, commonly used with the with statement.
65. Explain the difference between __str__() and __repr__().
    • Answer: __str__() is for end-user readable representation, while __repr__() is for debugging/developer representation.
66. What are Python magic (dunder) methods?
    • Answer: Special methods with double underscores (__init__, __add__) that define object behavior for operators and functions.
67. Explain how to create a virtual environment in Python.
    • Answer: Use python -m venv <env_name> to create an isolated environment.
68. How to handle JSON data in Python?
    • Answer: Use the json module with json.load(), json.dump(), json.loads(), and json.dumps().
69. What is argparse used for?
    • Answer: argparse is used for creating command-line interfaces by parsing arguments passed to the script.
70. Explain the asyncio module.
    • Answer: asyncio is used for asynchronous programming, managing coroutines, tasks, and events.
71. What is a weak reference in Python?
    • Answer: Weak references allow the referenced object to be garbage collected, used to avoid memory leaks.
72. How to secure Python code from SQL injection?
    • Answer: Use parameterized queries or ORM libraries like SQLAlchemy.
73. What is the pickle module?
    • Answer: pickle serializes Python objects to a byte stream and deserializes them back.
74. Explain the difference between shallow and deep copy.
    • Answer: Shallow copy duplicates the structure, while deep copy duplicates both structure and data recursively.
75. What is an abstract base class (ABC)?
    • Answer: ABCs define a blueprint for derived classes, enforced through the abc module.

This guide provides a wide range of Python interview questions, covering everything from basics to advanced topics. Let me know if you need a specific section or additional details!

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