Python Interview Questions & Answers

1. What is Python?

   • Answer: Python is a high-level, interpreted programming language known for its simplicity and readability. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming.

2. Explain the difference between Python 2 and Python 3.

   • Answer: Python 2 and Python 3 are two major versions of Python. Python 3 was designed to rectify some fundamental flaws in the design of Python 2, and it is not backward compatible with Python 2.

3. How does Python handle memory management?

   • Answer: Python uses a private heap space for storing objects and employs a garbage collector to manage memory. The garbage collector automatically deallocates memory occupied by objects that are no longer in use.

4. What is PEP 8?

   • Answer: PEP 8 is the Python Enhancement Proposal that provides style guide recommendations for writing readable and consistent Python code.

5. Explain Python's GIL (Global Interpreter Lock).

   • Answer: The Global Interpreter Lock is a mutex that protects access to Python objects, preventing multiple threads from executing Python bytecodes at once. This can limit the performance of multithreaded Python programs.

6. What is the purpose of the __init__ method in Python?

   • Answer: The __init__ method is a special method in Python classes that is automatically called when an object of the class is created. It is used to initialize the object's attributes.

7. What is a decorator in Python?

   • Answer: A decorator in Python is a design pattern that allows you to extend or modify the behavior of callable objects (functions or methods) without modifying their actual code.

8. Explain the difference between a list and a tuple in Python.

   • Answer: Lists are mutable, meaning their elements can be changed, added, or removed. Tuples are immutable, and their elements cannot be modified after creation.

9. What is the purpose of the __str__ method in Python?

   • Answer: The __str__ method is used to define the "informal" or user-friendly string representation of an object. It is called by the str() built-in function and the print() function.

10. What is a lambda function in Python?

    • Answer: A lambda function is an anonymous function created using the lambda keyword. It is often used for short, one-time operations where a full function definition would be overly verbose.

11. Explain the concept of list comprehensions in Python.

    • Answer: List comprehensions provide a concise way to create lists in Python. They consist of an expression followed by at least one for clause and zero or more if clauses.

12. What is the purpose of the with statement in Python?

    • Answer: The with statement is used to simplify resource management. It ensures that a context manager's __enter__ method is called before a block of code is executed and that the __exit__ method is called afterward.

13. How are exceptions handled in Python?

    • Answer: Exceptions in Python are handled using try, except, else, and finally blocks. Code that may raise an exception is placed inside the try block, and the corresponding exception-handling code is written in the except block.

14. What is the purpose of the pass statement in Python?

    • Answer: The pass statement in Python is a no-operation placeholder. It is used when syntactically some code is required, but no action is desired or necessary.

15. Explain the use of the *args and **kwargs in function definitions.

    • Answer: *args allows a function to accept any number of positional arguments, and **kwargs allows it to accept any number of keyword arguments.

16. What is a Python generator?

    • Answer: A generator in Python is a special type of iterator that allows you to iterate over a potentially large sequence of data without loading the entire sequence into memory at once.

17. How do you open and close a file in Python?

    • Answer: You can open a file using the open() function and close it using the close() method. Alternatively, you can use the with statement to automatically close the file when the block is exited.

18. Explain the purpose of the __name__ variable in Python.

    • Answer: The __name__ variable is a special variable in Python that is set to "__main__" if the Python script is being run directly. It is useful for determining whether a module is being imported or run as a standalone program.

19. What is the purpose of the __doc__ attribute in Python?

    • Answer: The __doc__ attribute is used to access the docstring (documentation string) of a Python object, such as a module, class, or function.

20. What is the self keyword in Python?

    • Answer: In Python, self is a conventional name used for the first parameter of a method in a class. It represents the instance of the object and is automatically passed when calling a method on an object.

21. What is the purpose of the enumerate() function in Python?

    • Answer: The enumerate() function is used to iterate over a sequence (such as a list or tuple) along with its index. It returns tuples containing the index and corresponding element.

22. Explain the purpose of the __init__.py file in Python.

    • Answer: The __init__.py file is used to indicate that a directory should be treated as a Python package. It may be empty or contain Python code to be executed when the package is imported.

23. What is the purpose of the super() function in Python?

    • Answer: The super() function is used to call a method from the parent class in an inheritance hierarchy. It is often used in the __init__ method of a derived class to invoke the parent class's constructor.

24. How do you perform shallow and deep copy in Python?

    • Answer: Shallow copy can be performed using the copy() method, while deep copy can be achieved using the copy.deepcopy() function from the copy module.

25. Explain the Global Interpreter Lock (GIL) in Python and its impact on multi-threading.

    • Answer: The Global Interpreter Lock (GIL) in Python is a mutex that protects access to Python objects. It prevents multiple threads from executing Python bytecodes at once, limiting the performance of multithreaded Python programs, especially in CPU-bound tasks.

26. What is a Python module and how do you import it?

    • Answer: A module in Python is a file containing Python definitions and statements. You can import a module using the import statement and access its attributes using dot notation.

27. **Ex

plain the difference between a shallow copy and a deep copy.** - Answer: A shallow copy creates a new object, but instead of copying the nested objects, it copies references to them. A deep copy creates a new object and recursively copies the objects found in the original, creating a fully independent copy.

28. What is the purpose of the __del__ method in Python?

    • Answer: The __del__ method is called when an object is about to be destroyed. It can be used to perform cleanup operations or resource deallocation.

29. How do you handle errors and exceptions in Python?

    • Answer: Errors and exceptions in Python are handled using try, except, else, and finally blocks. Code that may raise an exception is placed inside the try block, and the corresponding exception-handling code is written in the except block.

30. What are Python decorators and how do you use them?

    • Answer: Python decorators are a way to modify or extend the behavior of callable objects without modifying their actual code. Decorators are applied using the @decorator syntax before the function or method definition.

31. Explain the purpose of the __slots__ attribute in Python.

    • Answer: The __slots__ attribute in Python is used to explicitly declare the attributes that a class can have. It can be a tuple or list of attribute names, and it restricts the creation of new attributes.

32. What is the purpose of the itertools module in Python?

    • Answer: The itertools module provides a collection of fast, memory-efficient tools for working with iterators. It includes functions like count(), cycle(), and chain().

33. How do you reverse a list in Python?

    • Answer: You can reverse a list in Python using the reverse() method, or you can use slicing with a step of -1 (e.g., my_list[::-1]).

34. Explain the use of the * and ** operators in function arguments.

    • Answer: The * operator is used to unpack elements from an iterable (e.g., a list or tuple) in function arguments. The ** operator is used to unpack key-value pairs from a dictionary.

35. What is the purpose of the zip() function in Python?

    • Answer: The zip() function in Python is used to combine two or more iterables element-wise. It returns an iterator of tuples where the i-th tuple contains the i-th element from each of the input iterables.

36. Explain the use of the __call__ method in Python.

    • Answer: The __call__ method allows an object to be called as if it were a function. It is invoked when the object is called using the parentheses syntax.

37. What is the purpose of the all() and any() functions in Python?

    • Answer: The all() function returns True if all elements of an iterable are true (or if the iterable is empty). The any() function returns True if any element of the iterable is true. Both functions short-circuit as soon as a False value is encountered.

38. How do you find the length of a string in Python?

    • Answer: You can find the length of a string in Python using the len() function.

39. Explain the purpose of the filter() function in Python.

    • Answer: The filter() function in Python is used to construct an iterator from elements of an iterable for which a function returns True. It filters out elements based on the specified function.

40. What is the purpose of the map() function in Python?

    • Answer: The map() function in Python applies a given function to all items in an input list (or any iterable) and returns an iterator of the results.

41. How do you concatenate two lists in Python?

    • Answer: You can concatenate two lists in Python using the + operator or the extend() method.

42. Explain the purpose of the json module in Python.

    • Answer: The json module in Python is used for encoding and decoding JSON (JavaScript Object Notation) data. It provides methods like json.dumps() to convert Python objects to JSON strings and json.loads() to convert JSON strings to Python objects.

43. What is the purpose of the __dict__ attribute in Python?

    • Answer: The __dict__ attribute is a dictionary that contains an object's attributes and their values. It allows you to access and manipulate an object's attributes dynamically.

44. How do you remove duplicates from a list in Python?

    • Answer: You can remove duplicates from a list in Python by converting it to a set using set() or by using list comprehension with the not in condition.

45. What is a Python virtual environment?

    • Answer: A virtual environment in Python is a self-contained directory that contains a Python interpreter and a set of installed packages. It allows you to isolate dependencies for different projects.

46. Explain the purpose of the collections module in Python.

    • Answer: The collections module in Python provides specialized container datatypes, such as Counter, defaultdict, deque, and namedtuple, that are not available in the built-in types.