100 Python Interview Questions and Answers

Top 100 Python Interview Questions (With Answers): Ace Your Next Programming Job!

Unlock your dream Python developer job with these top 100 Python interview questions and answers! From beginner basics to advanced concepts, this comprehensive guide covers everything you need to ace technical interviews and boost your programming career.

Read more: Where and Why Should We Use “Django Shell”?

Basic Python Questions

1. What is Python?

Python is a high-level, object-oriented, interpreted programming language known for its simplicity and readability.

2. Difference between Python 2 and Python 3?

Python 3 is an improved version with several incompatibilities with Python 2, fixing many bugs and adding new features. Most modern projects use Python 3.

3. List the main data types in Python.

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

4. How do you declare a variable in Python?

Just use the variable name and assignment operator:

x = 5

5. How do you write comments in Python?

Single line:

# This is a comment

6. Difference between list and tuple?

Lists are mutable (can be changed); tuples are immutable.

7. How do you reverse a list?

my_list.reverse()

or

my_list[::-1]

8. How do you write a for loop?

for i in range(5):
    print(i)

9. How do you write a while loop?

i = 0
while i < 5:
    print(i)
    i += 1

10. Difference between “==” and “is”?

“==” checks for equality of value; “is” checks for object identity in memory.

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Intermediate Python Questions

11. What are lambda functions?

Anonymous, short functions defined with the lambda keyword.

square = lambda x: x**2

12. What are default arguments in functions?

Values that are used if the user does not supply arguments.

def func(x=5):
    print(x)

13. How do you create a dictionary?

my_dict = {"name": "Ali", "age": 25}

14. How do you get user input in Python?

Using the input() function:

name = input("Enter your name:")

15. What does the map function do?

Applies a function to every element in an iterable.

list(map(str, [1,2,3]))

16. What is the filter function?

Filters elements in an iterable based on a condition.

list(filter(lambda x : x > 0, [-1, 2, 1]))

17. What is a comprehension?

A concise way to generate lists, dicts, or sets.

new_list = [x*2 for x in range(5)] 

18. Why is Python called an “interpreted” language?

Because Python code is executed line by line by an interpreter, not compiled entirely before execution.

19. How do you convert a string to an integer?

int("123")  # Output: 123

20. What do break and continue do in loops?

break exits the loop, continue skips to the next iteration.

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Advanced Python Questions

21. What is a decorator and how is it defined?

A function that takes another function as an argument and returns a modified function.

def my_decorator(func):
    def wrapper():
        print("Before")
        func()
        print("After")
    return wrapper

@my_decorator
def hello():
    print("Hello World")

22. What is a generator?

A function that yields values one at a time and retains its state between calls.

def count_up_to(n):
    count = 1
    while count <= n:
        yield count
        count += 1

23. How do you handle exceptions?

Using try/except:

try:
    a = 5/0
except ZeroDivisionError:
    print("Division by zero!")

24. What is PEP8?

The official style guide for writing readable Python code.

25. What is a context manager?

For efficient resource management, like file handling.

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

26. Difference between deep copy and shallow copy?

Shallow copy copies references; deep copy copies everything recursively.

27. What is garbage collection in Python?

An automatic memory management mechanism that removes unused objects.

28. How can you optimize code performance?

Use efficient libraries (like NumPy), choose the right algorithms, avoid nested loops, and use generators.

29. What is multi-threading and GIL?

Multi-threading allows concurrent threads, but due to the Global Interpreter Lock (GIL), only one thread executes Python bytecode at a time.

30. What is async/await used for?

For asynchronous programming, mainly with I/O-bound tasks to improve performance.

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Object-Oriented Programming (OOP) in Python

31. What are classes and objects?

A class is a blueprint; an object is an instance of that class.

32. How do you define a class?

class Person:
    def __init__(self, name):
        self.name = name

33. What is self in classes?

Refers to the instance of the class within its methods.

34. What is inheritance?

A mechanism to derive a new class from an existing class.

35. What is polymorphism?

The ability for different objects to respond differently to the same method.

36. What is encapsulation?

Hiding data and methods within a class to restrict external access.

37. Difference between instance methods and class methods?

Instance methods act on object instances; class methods act on the class itself.

38. What is a static method?

A method not bound to the instance or class, defined with @staticmethod.

39. Purpose of str?

Returns a readable string representation of an object.

40. Purpose of init?

The constructor method called when an object is created.

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Popular Libraries and Tools

41. What is NumPy?

A popular library for numerical computations and array manipulation.

42. What is pandas used for?

Data analysis and manipulation with powerful DataFrame structures.

43. Difference between Series and DataFrame in pandas?

Series is a 1-D array; DataFrame is a 2-D table (like Excel).

44. Purpose of matplotlib?

To generate plots and graphical data visualizations.

45. Why use requests?

To send HTTP requests and work with APIs.

46. What is pip?

Python package manager for installing and managing libraries.

47. What does virtualenv do?

Creates isolated Python environments for projects.

48. What are unittest and pytest?

Libraries for writing and running automated tests.

49. Purpose of the re library?

For working with regular expressions.

50. What is dictionary comprehension?

A concise way to create dictionaries:

{x: x**2 for x in range(5)}

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Practical and Coding Questions

51. Program to count characters in a string.

string = "hello"
print(len(string))

52. Write a FizzBuzz program.

for i in range(1, 101):
    if i%3 == 0 and i%5 == 0:
        print("FizzBuzz")
    elif i%3 == 0:
        print("Fizz")
    elif i%5 == 0:
        print("Buzz")
    else:
        print(i)

53. How to read a file line by line?

with open('file.txt') as f:
    for line in f:
        print(line)

54. How to write to a file?

with open('output.txt', 'w') as f:
    f.write("Hello")

55. How to define a custom exception?

class MyError(Exception):
    pass

56. How to get unique elements from a list?

list(set([1, 2, 2, 3]))

57. Convert list to string?

",".join(['a', 'b', 'c'])

58. Convert string to list?

list("abc")

59. Separate even and odd numbers in a list?

even = [x for x in lst if x % 2 == 0]
odd = [x for x in lst if x % 2 != 0]

60. How to write a recursive function?

def factorial(n):
    if n == 0: return 1
    return n * factorial(n-1)

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Frameworks (Django, Flask)

61. What is Django?

A Python-based web framework for building professional websites.

62. What is Flask?

A minimal framework for building web services.

63. What is ORM in Django?

Object-Relational Mapping, letting you interact with your database using Python objects instead of SQL.

64. What are migrations in Django?

Versioned scripts to manage database schema changes.

65. What is a View in Django?

Code that processes an HTTP request and returns an HTTP response.

66. What is a Template in Django?

HTML code with placeholders to display dynamic data.

67. What is Blueprint in Flask?

A way to organize and modularize Flask applications.

68. How do you create a simple API in Django?

Use Django REST Framework and define appropriate views.

69. What is middleware?

Code that runs before or after processing an HTTP request.

70. What is a ModelForm in Django?

A form that is tied directly to a database model.

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Useful Tips & Tricks

71. How do you assign multiple variables at once?

a, b, c = 1, 2, 3

72. How do you swap two values quickly?

a, b = b, a

73. How to define a function with variable arguments?

def func(*args, **kwargs):
    pass

74. How do you remove elements from a list?

lst.remove(2)

or

lst.pop(0)

75. How to create a set?

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

76. Program to check if a string is a palindrome.

def is_palindrome(s):
    return s == s[::-1]

77. How do you merge two dictionaries?

dict1.update(dict2)

or

{**dict1, **dict2}

78. How do you use assert?

assert x > 0, "x must be positive"

79. Difference between ‘==’ and ‘in’?

‘==’ checks for equality; ‘in’ checks if an item exists in an iterable.

80. How do you round a number?

round(3.1415, 2)  # Output: 3.14

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Performance & Best Practice Questions

81. What is memoization?

Caching previous function results to speed up repeated calls.

82. What does the zip function do?

Combines multiple iterables element-wise.

list(zip([1, 2], ['a', 'b']))

83. What does enumerate do?

Returns both index and value while iterating.

for i, val in enumerate(lst):
    print(i, val)

84. Difference between append and extend in lists?

append adds a single new element, extend adds all elements of another list.

85. Difference between ‘classmethod’ and ‘staticmethod’?

classmethod gets class as the first argument; staticmethod doesn’t take any implicit first argument.

86. What do any and all do?

any returns True if at least one element is True; all returns True if every element is True.

87. How do you create a Python module?

Write your code in a .py file and import it wherever needed.

88. What is pip freeze?

Lists all installed packages and their versions in the current environment.

89. What is a docstring?

A multi-line comment used to document functions and classes.

def foo():
    """This is a docstring."""

90. How to use environment variables?

Using the os module:

import os
os.environ['MY_VAR']

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Challenging & Conceptual Questions

91. What does pass do?

It’s a no-operation statement—the code does nothing.

92. What is call used for?

Allows an object to be invoked as a function.

93. Difference between list comprehension and map?

Comprehensions are more readable and flexible; map is functional and sometimes faster.

94. When should you use with?

For efficient management of resources, especially files.

95. What does the init.py file do?

Turns a directory into a package.

96. Best practice for managing dependencies?

Use virtualenv or poetry with a requirements.txt file.

97. Difference between pickling and serialization?

Pickling is Python’s native serialization method, serialization is a general concept.

98. Are Design Patterns important in Python?

Yes, especially for large projects (Singleton, Factory, Observer, etc.).

99. Best way to learn Python?

Practice, solve real-world problems, and contribute to open-source projects.

100. Difference between SyntaxError and Exception?

SyntaxError occurs due to faulty code before execution; Exception happens at runtime.

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Conclusion

This list provides a comprehensive resource for preparing for any Python programming job interview. If you want a PDF version or need custom formatting for your website, let me know! I can also expand individual sections if you’d like more in-depth coverage.