106 Interview Questions and answers based on Python Programming Language | Er. Sahil

Basic Python Questions

1. Q: What is Python?
   A: Python is a high-level, interpreted programming language known for its readability and simplicity. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming.
2. Q: How is Python interpreted?
   A: Python code is executed by an interpreter, which reads and executes the code line by line, translating it into machine code at runtime.
3. Q: What are Python’s built-in data types?
   A: Python has several built-in data types, including integers, floats, strings, lists, tuples, sets, and dictionaries.
4. Q: Explain the difference between a list and a tuple.
   A: A list is mutable (can be changed) and defined with square brackets [ ], while a tuple is immutable (cannot be changed) and defined with parentheses ( ).
5. Q: How do you declare a variable in Python?
   A: You declare a variable by assigning a value to it, e.g., x = 5.
6. Q: What are Python functions?
   A: Functions in Python are reusable pieces of code that perform a specific task. They are defined using the def keyword.
7. Q: What is PEP 8?
   A: PEP 8 is the Python Enhancement Proposal which provides guidelines and best practices on how to write Python code.
8. Q: Explain what a dictionary is.
   A: A dictionary is a mutable, unordered collection of key-value pairs, defined using curly braces {}.
9. Q: How do you handle exceptions in Python?
   A: Exceptions are handled using try, except, and optionally finally blocks. E.g.:pythontry: x = 1 / 0 except ZeroDivisionError: print("Cannot divide by zero")
10. Q: What is a lambda function?
    A: A lambda function is an anonymous function defined with the lambda keyword, often used for short functions that are not reused. E.g., lambda x: x + 1.

Intermediate Python Questions

11. Q: How do you create a virtual environment in Python?
    A: You can create a virtual environment using the venv module:

bashpython -m venv myenv  

12. Q: Explain the concept of list comprehensions.
    A: List comprehensions provide a concise way to create lists. The syntax is [expression for item in iterable if condition]. E.g., [x**2 for x in range(10) if x % 2 == 0].
13. Q: What is the difference between == and is in Python?
    A: == checks for value equality while is checks for object identity (whether both operands point to the same object).
14. Q: What are *args and **kwargs?
    A: *args allows a function to accept any number of positional arguments, while **kwargs allows it to accept any number of keyword arguments.
15. Q: How do you read from and write to files in Python?
    A: You use the built-in open() function.

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

16. Q: What is a module in Python?
    A: A module is a file containing Python code (functions, classes, variables) that can be imported and used in other Python programs.
17. Q: Explain the difference between deep copy and shallow copy.
    A: A shallow copy creates a new object but inserts references into it to the objects found in the original. A deep copy creates a completely independent copy of the original object.
18. Q: What are decorators in Python?
    A: Decorators are a way to modify or enhance functions or methods without changing their code using the @decorator_name syntax.
19. Q: How can you sort a list in Python?
    A: You can sort a list using the sort() method or the sorted() function:

pythonmy_list.sort()  # In-place sorting  
sorted_list = sorted(my_list)  # Returns a new sorted list  

20. Q: What is the purpose of the self keyword in Python classes?
    A: self refers to the current instance of the class and is used to access class attributes and methods.

Advanced Python Questions

21. Q: How do you implement a queue using Python’s collections module?
    A: You can use deque from the collections module for an efficient queue implementation.

pythonfrom collections import deque  
queue = deque()  
queue.append('task1')  
queue.popleft()  

22. Q: What is the Global Interpreter Lock (GIL)?
    A: The GIL is a mutex that protects access to Python objects, preventing multiple native threads from executing Python bytecodes at once, which can limit parallel execution.
23. Q: Explain Python’s garbage collection mechanism.
    A: Python uses automatic garbage collection to manage memory, primarily through reference counting and cyclic garbage collection to reclaim memory occupied by unreachable objects.
24. Q: What is the difference between Python 2 and Python 3?
    A: Major differences include print as a function in Python 3, integer division behavior, Unicode support, and the removal of certain modules and built-in functions.
25. Q: How do you handle multiple exceptions in a single block?
    A: You can specify multiple exceptions in a single except block using a tuple.

pythontry:  
    # code that may raise exceptions  
except (TypeError, ValueError) as e:  
    print(f"An error occurred: {e}")  

26. Q: What are context managers in Python?
    A: Context managers allow you to allocate and release resources precisely when you want to. You can create them using with statements, typically for file operations.
27. Q: Explain how you can use the map() function in Python.
    A: The map() function applies a given function to all items in an iterable.

pythonresult = list(map(lambda x: x**2, [1, 2, 3, 4]))  # [1, 4, 9, 16]  

28. Q: What is the purpose of __init__.py?
    A: __init__.py is required to make Python treat directories as containing packages. The file can be empty or execute package initialization code.
29. Q: Explain the @staticmethod and @classmethod decorators.
    A: @staticmethod defines a method that does not depend on instance-specific data, while @classmethod defines a method that receives the class itself as the first argument.
30. Q: How can you profile a Python script?
    A: You can use the cProfile module to profile scripts and analyze their performance:

bashpython -m cProfile myscript.py  

Python Libraries and Frameworks

31. Q: What is NumPy?
    A: NumPy is a library for numerical computing in Python, providing support for large, multi-dimensional arrays and matrices, along with a collection of mathematical functions.
32. Q: What is Pandas primarily used for?
    A: Pandas is a data manipulation and analysis library that provides data structures like DataFrames for handling structured data easily.
33. Q: What does the matplotlib library do?
    A: Matplotlib is a plotting library for Python that provides tools for creating static, animated, and interactive visualizations in Python.
34. Q: What is Flask?
    A: Flask is a lightweight WSGI web application framework in Python that is easy to get started with and is suitable for small to medium-sized applications.
35. Q: What is Django?
    A: Django is a high-level web framework that encourages rapid development and clean, pragmatic design, offering an ORM, admin interface, and many built-in features.
36. Q: Explain the purpose of the requests library.
    A: The requests library simplifies making HTTP requests in Python, allowing you to send and receive data easily over the web.
37. Q: What is the use of the BeautifulSoup library?
    A: BeautifulSoup is a library for parsing HTML and XML documents, perfect for web scraping purposes.
38. Q: What is the purpose of the scikit-learn library?
    A: Scikit-learn is a machine learning library for Python that provides simple and efficient tools for data mining and data analysis.
39. Q: How do you create a RESTful API in Python?
    A: You can create a RESTful API using frameworks like Flask or Django REST framework by defining endpoints and handling HTTP methods.
40. Q: What is TensorFlow?
    A: TensorFlow is an open-source library for numerical computation and machine learning, providing a flexible framework for building deep learning models.

Python Best Practices

41. Q: How should you handle sensitive information in Python?
    A: Sensitive information should be stored securely, for instance, using environment variables or secure vaults, and never hard-coded in the source code.
42. Q: Explain the concept of unit testing in Python.
    A: Unit testing involves testing individual parts of a program for correctness. Python has a built-in module called unittest for writing and running tests.
43. Q: What are best practices for naming variables in Python?
    A: Use descriptive names, follow naming conventions (snake_case for variables and functions, CamelCase for classes), and avoid using reserved words.
44. Q: How do you ensure code quality in Python?
    A: You can ensure code quality by following PEP 8 guidelines, using linters like pylint or flake8, and writing tests.
45. Q: What is the importance of code comments and documentation?
    A: Code comments and documentation provide clarity about the code’s purpose, usage, and functionality, making it easier for others (and your future self) to understand and maintain.
46. Q: How do you optimize performance in Python?
    A: Performance can be optimized by using efficient algorithms, minimizing I/O operations, leveraging built-in functions, and using libraries like NumPy.
47. Q: What are common Python design patterns?
    A: Common design patterns include Singleton, Factory, Observer, and Strategy patterns, which help solve common problems in software design.
48. Q: How do you ensure compatibility with different Python versions?
    A: Use virtual environments, write Python 2/3 compatible code, and test your code in the intended environments.
49. Q: Explain the use of logging in Python.
    A: Logging in Python allows you to track events that happen when the software runs, which is useful for debugging and monitoring. The logging module provides a flexible framework for emitting log messages.
50. Q: What is dependency management in Python?
    A: Dependency management involves handling package installations and versions, typically done using tools like pip and requirements.txt.

Python Concepts

51. Q: What is multithreading in Python?
    A: Multithreading allows multiple threads to be executed concurrently, but due to the GIL, Python threads are not suitable for CPU-bound tasks.
52. Q: Difference between synchronous and asynchronous programming?
    A: Synchronous programming executes tasks sequentially, while asynchronous programming allows tasks to be executed concurrently, making it more efficient for I/O-bound tasks.
53. Q: What is the significance of the init method in Python classes?
    A: The __init__ method initializes a newly created object, allowing you to set initial values for the attributes.
54. Q: Explain the term “duck typing” in Python.
    A: Duck typing is a concept in Python where the type or class of an object is less important than the methods it defines or the operations it supports.
55. Q: What are exceptions in Python?
    A: Exceptions are events that disrupt the normal flow of a program. They can be handled using try-except blocks to prevent crashes.
56. Q: What is a for loop in Python?
    A: A for loop is used to iterate over a sequence (like a list or a string) and execute a block of code for each item in the sequence.
57. Q: How do you create a class in Python?
    A: A class is defined using the class keyword, followed by the class name.

pythonclass MyClass:  
    def __init__(self):  
        self.variable = 1  

58. Q: Explain the concept of inheritance in Python.
    A: Inheritance allows a class (child) to inherit attributes and methods from another class (parent), promoting code reusability.
59. Q: What are generators in Python?
    A: Generators are a way to create iterators using the yield keyword to produce a series of values one at a time, instead of storing them in memory.

Python Concepts (Cont’d)

61. Q: What is monkey patching in Python?
    A: Monkey patching refers to the practice of modifying or extending libraries or classes at runtime. This can involve adding or altering methods and attributes, although it should be done with caution, as it can lead to code that is hard to maintain.
62. Q: How can you measure the execution time of a Python program?
    A: The execution time can be measured using the time module:

pythonimport time  
start_time = time.time()  
# code to measure  
end_time = time.time()  
print(f"Execution time: {end_time - start_time} seconds")  

63. Q: What is the purpose of the with statement?
    A: The with statement simplifies exception handling by encapsulating common preparation and cleanup tasks in so-called context managers, automatically handling resource management (like closing files).
64. Q: Explain the difference between a process and a thread.
    A: A process is an independent program that runs in its own memory space, while a thread is a smaller unit of a process that can share memory space with other threads, allowing for concurrent execution.
65. Q: What is the async and await keywords used for in Python?
    A: The async keyword is used to define an asynchronous function, while await is used to pause the execution of the async function until the awaited task is completed, allowing for non-blocking I/O operations.
66. Q: How do you merge two dictionaries in Python?
    A: You can merge two dictionaries using the update() method or the dictionary unpacking method in Python 3.5 and later:

pythondict1 = {'a': 1, 'b': 2}  
dict2 = {'b': 3, 'c': 4}  
dict1.update(dict2)  # dict1 becomes {'a': 1, 'b': 3, 'c': 4}  
merged_dict = {**dict1, **dict2}  # {'a': 1, 'b': 3, 'c': 4}  

67. Q: What is the enumerate() function useful for?
    A: The enumerate() function adds a counter to an iterable and returns it as an enumerate object, which can be useful for keeping track of the index in loops:

pythonfor index, value in enumerate(['a', 'b', 'c']):  
    print(index, value)  # 0 a, 1 b, 2 c  

68. Q: What are properties in Python?
    A: Properties in Python are a way to manage the attributes of a class using getters and setters without changing the syntax of attribute access. They are defined using the @property decorator.
69. Q: How can you schedule a task in Python?
    A: You can schedule a task using libraries like schedule or APScheduler. For example, using schedule:

pythonimport schedule  
import time  

def job():  
    print("Job running...")  

schedule.every(10).seconds.do(job)  

while True:  
    schedule.run_pending()  
    time.sleep(1)  

70. Q: Explain the Python super() function.
    A: The super() function returns a temporary object of the superclass that allows you to call its methods. It’s commonly used in class inheritance to avoid directly referencing the parent class.

Advanced Python Libraries and Concepts

71. Q: How do you create a custom exception in Python?
    A: You can create a custom exception by defining a new class that inherits from the built-in Exception class.

pythonclass MyCustomError(Exception):  
    pass  

72. Q: What is the purpose of the itertools module?
    A: The itertools module provides various functions that create iterators for efficient looping, including functions for counting, grouping, and generating combinations and permutations.
73. Q: How do you sort a dictionary by its values?
    A: You can sort a dictionary by its values using the sorted() function along with a lambda function:

pythonmy_dict = {'a': 3, 'b': 1, 'c': 2}  
sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1]))  

74. Q: What is the purpose of multiprocessing in Python?
    A: The multiprocessing module allows you to create multiple processes, bypassing the GIL and allowing for true parallelism, which is useful for CPU-bound tasks.
75. Q: How can you read a CSV file in Python?
    A: You can read a CSV file using the built-in csv module or using the pandas library for more complex operations:

pythonimport csv  
with open('file.csv', newline='') as csvfile:  
    reader = csv.reader(csvfile)  
    for row in reader:  
        print(row)  

76. Q: What is the role of __str__ and __repr__ methods in a class?
    A: The __str__ method is used to define a string representation for the class that is user-friendly, while the __repr__ method is used to define an unambiguous representation that is meant for developers.
77. Q: How do you serialize an object in Python?
    A: You can serialize an object to a byte stream using the pickle module:

pythonimport pickle  
serialized_obj = pickle.dumps(my_object)  

78. Q: What is the difference between shallow copy and deep copy?
    A: Shallow copy creates a new object but inserts references into it to the original nested objects. Deep copy creates a completely independent copy of the entire object and all its nested objects using the copy module.
79. Q: Explain what assert is used for in Python.
    A: assert is used to perform debugging assertions. It tests a condition and raises an AssertionError if the condition is False, helping to identify bugs in the code.
80. Q: How do you ensure that a block of code is only executed once?
    A: You can use the if __name__ == "__main__": statement to ensure that a block of code runs only when the script is executed directly, not when imported as a module.

Miscellaneous Python Questions

81. Q: What is the __dict__ attribute in Python?
    A: __dict__ is a special attribute in Python that stores an object’s writable attributes in a dictionary form.
82. Q: Describe what a closure is in Python.
    A: A closure is a function that retains access to its lexical scope, even when the function is invoked outside that scope, allowing it to remember the values of its variables.
83. Q: What are f-strings in Python?
    A: F-strings (formatted string literals) allow you to embed expressions inside string literals, using curly braces {}. They are prefixed with f.

pythonname = "John"  
greeting = f"Hello, {name}!"  

84. Q: How do you implement inheritance in Python?
    A: You implement inheritance by defining a new class that inherits from an existing class:

pythonclass Parent:  
    pass  

class Child(Parent):  
    pass  

85. Q: What is the use of the finally block in exception handling?
    A: A finally block is used to execute code no matter the outcome of the try-except blocks, typically for cleanup actions like closing files or releasing resources.
86. Q: How do you create and run tests in Python?
    A: You can create tests using the unittest module or the pytest framework, then run tests directly from the command line or within an IDE.
87. Q: What is type hinting in Python?
    A: Type hinting allows you to specify the expected data types of variables, function parameters, and return values using annotations, enhancing code readability and aiding static analysis.
88. Q: How do you reverse a list in Python?
    A: You can reverse a list using the reverse() method or slicing:

pythonmy_list.reverse()  # In-place reversal  
reversed_list = my_list[::-1]  # Returns a new reversed list  

89. Q: What is the difference between a shallow copy and deep copy?
    A: A shallow copy creates a new object but inserts references into it to the original nested objects, while a deep copy creates a completely independent copy of the entire object and its nested objects.
90. Q: How do you handle time and date in Python?
    A: You can handle date and time using the datetime module to create, manipulate, and format dates and times.

Final Set of Python Questions

91. Q: What is the purpose of the try-except block?
    A: The try-except block is used to catch exceptions and errors without crashing the program, allowing for graceful handling of unexpected situations.
92. Q: How do you import modules in Python?
    A: You can import modules using the import statement. You can import the entire module or specific functions/classes from it.

pythonimport math  # Import entire module  
from math import sqrt  # Import specific function  

93. Q: What is the os module used for?
    A: The os module provides a way to use operating system-dependent functionality, such as reading or writing to the file system, managing directories, and executing shell commands.
94. Q: What are the differences between append() and extend() in lists?
    A: append() adds its argument as a single element at the end of a list, while extend() iterates over its argument adding each element to the list.
95. Q: How can you check if a key exists in a dictionary?
    A: You can check if a key exists in a dictionary using the in keyword: if key in my_dict:.
96. Q: What is list slicing in Python?
    A: List slicing allows you to access a range of items in a list by specifying a start and stop index, as well as a step.

pythonmy_list = [0, 1, 2, 3, 4, 5]  
slice = my_list[1:4]  # returns [1, 2, 3]  

97. Q: How do you convert a list to a string in Python?
    A: You can convert a list to a string using the join() method:

pythonmy_list = ['a', 'b', 'c']  
my_string = ''.join(my_list)  # 'abc'  

98. Q: What is the difference between float() and int()?
    A: float() converts a number or a string to a floating-point number, while int() converts a number or a string to an integer by truncating decimals.
99. Q: How do you remove duplicate elements from a list?
    A: You can remove duplicates by converting the list to a set and back to a list:

pythonunique_list = list(set(my_list))  

100. Q: Describe what a package is in Python.
     A: A package is a way of organizing related modules in a directory hierarchy, typically containing an __init__.py file to indicate that the directory should be treated as a package.
101. Q: What is an API in Python?
     A: An API (Application Programming Interface) in Python is a set of protocols and tools for building software and applications, often allowing different software components to communicate.
102. Q: How can you find all the methods in a module or object?
     A: You can use the dir() function to list all attributes and methods of a module or object:
     python dir(module)
103. Q: What are iterators and iterables in Python?
     A: An iterable is an object that can return its elements one at a time, and an iterator is an object that represents a stream of data, providing a method __next__() to get the next item and a __iter__() method for initialization.
104. Q: Explain the use of sys module in Python.
     A: The sys module provides access to interpreter variables and functions, allowing interaction with the Python runtime environment, such as command-line arguments, exiting the program, and manipulating the Python path.
105. Q: How can you create a multi-threaded application in Python?
     A: You can create a multi-threaded application using the threading module to create and manage threads.
     “`python
     import threading

rubydef worker():  

scss    print("Thread working")  

thread = threading.Thread(target=worker)  
thread.start()  
```  

106. Q: What is the json module used for in Python?
A: The json module provides methods for parsing JSON data into Python objects and converting Python objects back into JSON format.