Python Interview Questions

These python questions range from basic to advanced levels, covering various aspects of Python programming, including syntax, data structures, functions, modules, and more.

 Basic Python Questions

1. What is Python?

Answer: Python is a high-level, interpreted programming language known for its easy-to-read syntax and versatility. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming.

2. What are the key features of Python?

  – Answer: Some key features of Python include:

  – Easy to read and write.

  – Interpreted language.

  – Dynamically typed.

  – Extensive standard library.

  – Open-source with a large community.

  – Supports multiple programming paradigms.

3. What is PEP 8?

   Answer: PEP 8 is the Python Enhancement Proposal that outlines the style guide for writing clean and readable Python code. It provides conventions for formatting Python code, including indentation, naming conventions, and more.

4. How is Python an interpreted language?

   – Answer: Python is considered an interpreted language because its code is executed line by line by the Python interpreter at runtime, rather than being compiled into machine code.

5. What is the difference between a list and a tuple in Python?

   – Answer: The primary difference is that lists are mutable (i.e., their elements can be changed), while tuples are immutable (i.e., their elements cannot be changed after they are created).

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

   – Answer: Python’s built-in data types include:

  – Numeric types: int, float, complex

  – Sequence types: list, tuple, range

  – Text type: str

  – Mapping type: dict

  – Set types: set, frozenset

  – Boolean type: bool

  – Binary types: bytes, bytearray, memoryview

7. What is a dictionary in Python?

   – Answer: A dictionary in Python is an unordered collection of key-value pairs. Each key is unique and used to retrieve the corresponding value. Dictionaries are defined using curly braces {}.

8. How do you create a virtual environment in Python?

– Answer: You can create a virtual environment using the following command:

python -m venv myenv

This command creates a directory myenv with the necessary files to run Python in isolation.

9. How do you handle exceptions in Python?

– Answer: Exceptions in Python are handled using the try-except block. You can catch specific exceptions or handle them generally. Example:

try:

x = 1 / 0

except ZeroDivisionError:

print(“You cannot divide by zero!”)

10. What is the difference between == and is in Python?

– Answer: == checks for equality of values, while is checks for identity, meaning it checks if two variables point to the same object in memory.

Intermediate Python Questions

11. What are Python decorators?

– Answer: Decorators are a way to modify or enhance the behavior of a function or method. They are functions that take another function as an argument and extend its behavior without explicitly modifying it.

12. Explain list comprehension in Python.

– Answer: List comprehension is a concise way to create lists. It consists of brackets containing an expression followed by a for clause. Example:

squares = [x2 for x in range(10)]

13. What is a lambda function?

– Answer: A lambda function is an anonymous function expressed as a single line. It can take multiple arguments but has only one expression. Example:

add = lambda x, y: x + y

14. What is the self keyword in Python?

– Answer: The self keyword represents the instance of the class and is used to access variables and methods associated with the current object.

15. How do you reverse a list in Python?

– Answer: You can reverse a list using the reverse() method or slicing:

my_list.reverse()

reversed_list = my_list[::-1]

16. What is the purpose of __init__ in Python?

– Answer: __init__ is a special method in Python (a constructor) used to initialize the attributes of an object when it’s created.

17. What is the difference between append() and extend() in Python?

– Answer: append() adds a single element to the end of a list, while extend() adds multiple elements from another iterable to the end of the list.

18. What are Python generators?

– Answer: Generators are functions that return an iterable set of items, one at a time, using the yield statement. They are useful for creating iterators with less memory consumption.

19. Explain the difference between deepcopy and shallow copy.

– Answer: A shallow copy creates a new object but doesn’t create copies of nested objects. A deep copy creates a new object and recursively copies all objects within the original.

20. What is GIL in Python?

– Answer: The Global Interpreter Lock (GIL) is a mutex that protects access to Python objects, preventing multiple threads from executing Python bytecodes simultaneously in a single process.

Advanced Python Questions

21. What are Python metaclasses?

– Answer: A metaclass in Python is a class of a class that defines how a class behaves. Metaclasses allow for the modification of class behavior at the time of creation.

22. How do you manage memory in Python?

– Answer: Python manages memory using a private heap containing all objects and data structures. The memory manager handles memory allocation, deallocation, and garbage collection.

23. What is the with statement in Python?

– Answer: The with statement simplifies exception handling by automatically acquiring and releasing resources, such as file streams. It ensures that clean-up code is executed.

24. How do you implement a Singleton design pattern in Python?

– Answer: A Singleton ensures that only one instance of a class is created. You can implement it using a class-level variable or metaclasses.

25. What is monkey patching in Python?

– Answer: Monkey patching refers to modifying or extending a module or class at runtime. It can be used to change behavior without altering the original source code.

26. Explain the use of super() in Python.

– Answer: super() is used to call a method from a parent class in the context of the current class. It is commonly used to extend or override parent class methods.

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

– Answer: Python has many built-in functions, including len(), max(), min(), sum(), sorted(), type(), and dir(). These functions are always available for use.

28. How do you perform unit testing in Python?

– Answer: Python provides a built-in module called unittest for creating and running tests. Tests are organized into classes and methods, and the framework handles assertions and test results.

29. What is the __repr__ method in Python?

– Answer: __repr__ is a special method used to define a string representation of an object for debugging and logging purposes. It should return a string that is a valid Python expression.

30. Explain method resolution order (MRO) in Python.

– Answer: MRO is the order in which methods are inherited in the presence of multiple inheritance. Python uses the C3 linearization algorithm to determine the order.

Python Data Structures

31. How do you create a set in Python?

– Answer: A set is created by placing elements inside curly braces {} or using the set() function. Example:

my_set = {1, 2, 3}

my_set = set([1, 2, 3])

32. What is the difference between a list and a dictionary?

– Answer: A list is an ordered collection of elements indexed by their position, while a dictionary is an unordered collection of key-value pairs.

33. How do you sort a list in Python?

– Answer: You can sort a list using the sort() method or the sorted() function. Example:

my_list.sort()

sorted_list = sorted(my_list)

34. What is the difference between remove(), pop(), and del in Python?

– Answer:

– remove(): Removes the first occurrence of a value.

– pop(): Removes and returns an element at a specific index.

– del: Deletes an element at a specific index or slices.

35. How do you convert a list to a tuple in Python?

– Answer: You can convert a list to a tuple using the tuple() function. Example:

my_tuple = tuple(my_list)

36. What is a frozenset in Python?

– Answer: A frozenset is an immutable version of a set. Once created, the elements of a frozenset cannot be modified.

37. How do you merge two dictionaries in Python?

– Answer: In Python 3.9 and later, you can merge dictionaries using the | operator. In earlier versions, use the update() method.

38. What is a defaultdict in Python?

– Answer: A defaultdict is a subclass of dict that provides a default value for nonexistent keys. It is part of the collections module.

39. How do you count occurrences of elements in a list?

– Answer: You can count occurrences using the count() method or using collections.Counter. Example:

from collections import Counter

counts = Counter(my_list)

40. How do you flatten a nested list in Python?

– Answer: You can flatten a nested list using list comprehension or recursion. Example:

flat_list = [item for sublist in nested_list for item in sublist]

Python Functions and Modules

41. What is the difference between a function and a method in Python?

– Answer: A function is a block of code that performs a specific task and can be called independently, while a method is a function associated with an object (class instance) and called on that object.

42. How do you pass arguments to a function in Python?

– Answer: Arguments can be passed to a function in Python using positional arguments, keyword arguments, or a combination of both.

43. What are args and kwargs in Python?

– Answer: args allows you to pass a variable number of positional arguments, while kwargs allows you to pass a variable number of keyword arguments to a function.

44. What is the purpose of the return statement in a function?

– Answer: The return statement is used to exit a function and return a value to the caller.

45. How do you import a module in Python?

– Answer: You can import a module using the import statement. Example:

import math

from math import sqrt

46. What is the __name__ variable in Python?

– Answer: The __name__ variable is a special variable that holds the name of the module. It is used to check if a module is being run directly or imported elsewhere.

47. What are Python namespaces?

– Answer: Namespaces in Python are containers for mapping names to objects. They are used to avoid naming conflicts and are implemented as dictionaries.

48. How do you define a recursive function in Python?

– Answer: A recursive function is a function that calls itself. It must have a base case to terminate recursion. Example:

def factorial(n):

if n == 0:

return 1

return n  factorial(n – 1)

49. What is a module in Python?

– Answer: A module is a file containing Python code, such as functions, classes, or variables, that can be imported and reused in other programs.

50. What is the difference between a module and a package in Python?

– Answer: A module is a single file containing Python code, while a package is a collection of modules organized in directories, containing an __init__.py file.

Python Object-Oriented Programming

51. What is object-oriented programming (OOP)?

– Answer: OOP is a programming paradigm based on the concept of objects, which are instances of classes that encapsulate data and behavior.

52. What are classes and objects in Python?

– Answer: A class is a blueprint for creating objects, defining their attributes and methods. An object is an instance of a class with specific values for the attributes defined in the class.

53. What is inheritance in Python?

– Answer: Inheritance allows a class (child class) to inherit attributes and methods from another class (parent class), promoting code reuse and organization.

54. What is polymorphism in Python?

– Answer: Polymorphism allows objects of different classes to be treated as objects of a common parent class, typically by overriding methods in the child classes.

55. What is encapsulation in Python?

– Answer: Encapsulation is the concept of bundling data (attributes) and methods that operate on that data into a single unit, or class. It also involves restricting direct access to some of the object’s components.

56. What is method overloading in Python?

– Answer: Method overloading is not directly supported in Python, but you can achieve similar behavior using default arguments or args and kwargs.

57. What is method overriding in Python?

– Answer: Method overriding occurs when a child class provides a specific implementation of a method that is already defined in its parent class.

58. What is multiple inheritance in Python?

– Answer: Multiple inheritance occurs when a class inherits from more than one parent class, combining attributes and methods from all parent classes.

59. What is an abstract class in Python?

– Answer: An abstract class is a class that cannot be instantiated directly and is meant to be subclassed. It typically contains one or more abstract methods, which must be implemented by subclasses.

60. What are __str__ and __repr__ methods in Python?

– Answer: __str__ returns a human-readable string representation of an object, while __repr__ returns a more formal string representation, typically used for debugging.

Python File Handling

61. How do you open a file in Python?

– Answer: You can open a file using the open() function, specifying the filename and mode (‘r’, ‘w’, ‘a’, etc.). Example:

file = open(‘file.txt’, ‘r’)

62. How do you read a file in Python?

– Answer: You can read a file using methods like read(), readline(), or readlines(). Example:

content = file.read()

63. How do you write to a file in Python?

– Answer: You can write to a file using the write() or writelines() methods. Example:

file.write(‘Hello, World!’)

64. How do you close a file in Python?

– Answer: You close a file using the close() method to release the file resource. Example:

file.close()

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

– Answer: read() reads the entire content of a file as a single string, while readlines() reads the file line by line and returns a list of strings.

66. How do you use the with statement for file handling?

– Answer: The with statement automatically closes the file when the block is exited, even if an exception occurs. Example:

with open(‘file.txt’, ‘r’) as file:

content = file.read()

67. How do you check if a file exists in Python?

– Answer: You can check if a file exists using the os.path.exists() method. Example:

import os

exists = os.path.exists(‘file.txt’)

68. How do you delete a file in Python?

– Answer: You can delete a file using the os.remove() function. Example:

os.remove(‘file.txt’)

69. How do you rename a file in Python?

– Answer: You can rename a file using the os.rename() function. Example:

os.rename(‘old_name.txt’, ‘new_name.txt’)

70. How do you copy a file in Python?

– Answer: You can copy a file using the shutil.copy() function. Example:

import shutil

shutil.copy(‘source.txt’, ‘destination.txt’)

Python Libraries and Frameworks

71. What is NumPy?

– Answer: NumPy is a powerful library for numerical computing in Python. It provides support for large multi-dimensional arrays and matrices, along with a collection of mathematical functions to operate on these arrays.

72. What is Pandas?

– Answer: Pandas is a data manipulation and analysis library in Python, providing data structures like DataFrames and Series that make it easy to work with structured data.

73. What is Matplotlib?

– Answer: Matplotlib is a plotting library in Python that allows for the creation of static, interactive, and animated visualizations in a variety of formats.

74. What is Django?

– Answer: Django is a high-level web framework in Python that encourages rapid development and clean, pragmatic design. It follows the “batteries-included” philosophy, providing many built-in features.

75. What is Flask?

– Answer: Flask is a lightweight web framework in Python.

It is known for its simplicity and flexibility, allowing developers to build web applications with minimal overhead.

76. What is TensorFlow?

– Answer: TensorFlow is an open-source machine learning library developed by Google. It provides tools and libraries for building and training deep learning models.

77. What is the difference between pip and conda?

– Answer: pip is a package manager for Python packages from the Python Package Index (PyPI), while conda is a package manager for Python and other languages, including tools, libraries, and dependencies.

78. How do you install a Python package?

– Answer: You can install a Python package using pip. Example:

pip install package_name

79. What is scikit-learn?

– Answer: Scikit-learn is a machine learning library in Python that provides simple and efficient tools for data mining and data analysis, built on NumPy, SciPy, and Matplotlib.

80. What is PyTorch?

– Answer: PyTorch is an open-source machine learning library developed by Facebook, known for its flexibility and ease of use, especially in deep learning research and applications.

Python Best Practices

81. What is the Zen of Python?

– Answer: The Zen of Python is a collection of guiding principles for writing computer programs in Python, written by Tim Peters. It can be accessed by typing import this in the Python interpreter.

82. How do you manage dependencies in Python projects?

– Answer: Dependencies in Python projects are typically managed using a requirements.txt file or a Pipfile, which lists all the necessary packages and their versions.

83. What are Python docstrings?

– Answer: Docstrings are multi-line strings that describe the purpose and usage of a function, class, or module. They are placed right after the definition and are accessible via the __doc__ attribute.

84. What is linting in Python?

– Answer: Linting is the process of analyzing code to detect potential errors, stylistic issues, and bugs. Tools like pylint and flake8 are commonly used for linting Python code.

85. How do you handle circular imports in Python?

– Answer: Circular imports occur when two or more modules import each other. This can be resolved by restructuring code, using local imports, or using import statements inside functions or methods.

86. How do you optimize Python code for performance?

– Answer: Python code can be optimized by:

– Using built-in functions and libraries.

– Avoiding unnecessary loops and computations.

– Using list comprehensions and generator expressions.

– Profiling code to identify bottlenecks.

87. What is a Pythonic way to merge two lists?

– Answer: The Pythonic way to merge two lists is to use the + operator or list comprehension:

merged_list = list1 + list2

88. How do you handle large datasets in Python?

– Answer: Large datasets can be handled using libraries like pandas, dask, or PySpark, which provide tools for working with large data in chunks, parallel processing, and distributed computing.

89. What is a context manager in Python?

– Answer: A context manager is an object that manages the setup and teardown of resources, ensuring that they are properly acquired and released. It is typically used with the with statement.

90. How do you implement logging in Python?

– Answer: Python’s logging module is used to implement logging, allowing you to track events that happen during program execution. Example:

import logging

logging.basicConfig(level=logging.INFO)

logging.info(‘This is an info message.’)

Python Advanced Topics

91. What is concurrency in Python?

– Answer: Concurrency in Python refers to the ability of a program to perform multiple tasks at the same time, typically using threads, processes, or asynchronous programming.

92. What is asynchronous programming in Python?

– Answer: Asynchronous programming in Python allows you to write code that performs non-blocking operations using async and await keywords, enabling tasks to run concurrently.

93. What is the difference between multiprocessing and multithreading?

– Answer:

– Multiprocessing: Involves multiple processes, each with its own memory space, allowing for parallel execution on multiple CPU cores.

– Multithreading: Involves multiple threads within a single process, sharing memory space, allowing for concurrent execution but constrained by the GIL.

94. What is a coroutine in Python?

– Answer: A coroutine is a special function in Python defined with async def, which can be paused and resumed, allowing asynchronous programming.

95. How do you handle memory leaks in Python?

– Answer: Memory leaks can be handled by identifying and freeing up resources using tools like gc (garbage collection), monitoring reference counts, and ensuring proper resource management.

96. What are Python descriptors?

– Answer: Descriptors are objects that define how attributes of a class are accessed or modified. They implement methods like __get__(), __set__(), and __delete__().

97. What is the weakref module in Python?

– Answer: The weakref module allows you to create weak references to objects, which do not prevent the object from being garbage collected. This is useful for caching and avoiding memory leaks.

98. What is the itertools module in Python?

– Answer: The itertools module provides a collection of fast, memory-efficient tools for creating iterators that produce complex iterables from simple ones.

99. How do you write a generator in Python?

– Answer: A generator is written using a function with one or more yield statements, which return values one at a time, maintaining the function’s state between calls.

100. What is the functools module in Python?

– Answer: The functools module provides higher-order functions that act on or return other functions. Examples include partial, reduce, lru_cache, and wraps.