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Python


Interview Questions For Python


1. What is Python, and what are its key features?
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Ans. Python is a high-level, interpreted programming language known for its simplicity and readability. Key features include:

  • Easy to learn and read.
  • Dynamic typing and automatic memory management.
  • Large standard library and community support.
  • Supports object-oriented, procedural, and functional programming.
  • Extensive third-party libraries and frameworks.
2. What are Python's main data types?
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Ans. Python supports several built-in data types:

  • int – Integer numbers
  • float – Floating-point numbers
  • str – Strings
  • list – Ordered, mutable collection
  • tuple – Ordered, immutable collection
  • dict – Key-value pairs
  • set – Unordered collection of unique items
  • bool – Boolean values
3. What is a Python decorator?
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Ans. A decorator is a function that extends the behavior of another function without modifying it directly.

def decorator(func):
    def wrapper():
        print("Before function call")
        func()
        print("After function call")
    return wrapper

@decorator
def say_hello():
    print("Hello!")

say_hello()
4. Explain the concept of inheritance in Python.
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Ans. Inheritance allows one class (child) to inherit attributes and methods from another (parent).

class Animal:
    def speak(self):
        print("Animal speaks")

class Dog(Animal):
    def speak(self):
        print("Dog barks")

dog = Dog()
dog.speak()  # Outputs: Dog barks
5. What is the difference between a shallow copy and a deep copy?
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Ans. A shallow copy creates a new object but not nested objects. A deep copy copies the object and all nested objects recursively.

6. What is the difference between Python 2 and Python 3?
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Ans. Key differences include:

  • print is a function in Python 3, not a statement.
  • Integer division returns a float in Python 3.
  • Strings are Unicode by default in Python 3.
  • Python 2 is no longer officially supported.
7. What is a lambda function in Python?
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Ans. A lambda function is a small anonymous function defined with the lambda keyword.

add = lambda x, y: x + y
print(add(3, 4))  # Outputs: 7
8. What is the difference between is and == in Python?
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Ans. == checks if values are equal. is checks if two references point to the same object in memory.

9. What is a Python generator, and how is it different from a normal function?
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Ans. A generator uses yield to return values one at a time. It can be paused and resumed, making it memory-efficient.

def my_generator():
    yield 1
    yield 2
    yield 3

gen = my_generator()
print(next(gen))  # Outputs: 1
print(next(gen))  # Outputs: 2
10. What are Python's built-in data structures?
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Ans. Python's built-in data structures include:

  • List – Mutable and ordered
  • Tuple – Immutable and ordered
  • Set – Mutable and unordered, unique elements
  • Dictionary – Mutable and unordered, key-value pairs
11. What is the difference between lists and tuples in Python?
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Ans. Lists are mutable and can be changed after creation, whereas tuples are immutable and cannot be modified.

12. How is memory managed in Python?
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Ans. Python uses a private heap space and automatic garbage collection. The memory manager allocates memory and the garbage collector reclaims unused memory.

13. What is the use of the with statement in Python?
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Ans. The with statement is used to wrap the execution of a block with methods defined by a context manager. It ensures proper acquisition and release of resources.

with open('file.txt') as f:
    data = f.read()
14. What are args and kwargs in Python?
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Ans. *args is used to pass a variable number of positional arguments, while **kwargs passes keyword arguments.

def func(*args, **kwargs):
    print(args)
    print(kwargs)
15. What are Python modules and packages?
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Ans. A module is a single Python file containing functions and classes. A package is a directory containing multiple modules and an __init__.py file.

16. How does exception handling work in Python?
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Ans. Python uses try, except, else, and finally blocks to handle exceptions.

try:
    x = 1 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")
17. What are Python's scopes of variables?
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Ans. Python uses the LEGB rule: Local, Enclosing, Global, Built-in to determine variable scope.

18. What is the difference between deep and shallow copy?
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Ans. A shallow copy creates a new object but inserts references into it, whereas a deep copy creates a new object and recursively copies all objects inside it.

19. What is a Python iterator?
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Ans. An iterator is an object that can be iterated upon using the __iter__() and __next__() methods.

20. What is the difference between a function and a method in Python?
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Ans. A function is defined using def and can be standalone. A method is a function associated with an object/class.

21. How do you manage packages in Python?
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Ans. Python uses pip (Python Package Installer) to install and manage third-party packages.

pip install package-name
22. What is list comprehension?
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Ans. List comprehension is a concise way to create lists.

squares = [x**2 for x in range(5)]
23. What are Python's built-in functions?
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Ans. Python provides several built-in functions like len(), type(), range(), sum(), max(), min(), etc.

24. What is the difference between global and nonlocal keywords?
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Ans. global is used to declare a global variable inside a function. nonlocal is used in nested functions to refer to a variable in the nearest enclosing scope.

25. How do you open and read a file in Python?
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Ans. Use the open() function and methods like read(), readline(), or iterate through the file object.

with open("file.txt", "r") as file:
    content = file.read()
26. What are Python’s magic methods?
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Ans. Magic methods (also called dunder methods) are special methods with double underscores like __init__, __str__, __len__, __add__, etc., used to customize object behavior.

27. What is the use of the pass statement in Python?
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Ans. pass is a placeholder statement used when no action is required. It helps define empty classes, functions, or loops.

28. What is the difference between del, remove(), and pop()?
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Ans.

  • del deletes by index or variable reference.
  • remove() removes the first matching value.
  • pop() removes and returns the item at a given index.
29. What is duck typing in Python?
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Ans. Duck typing is a concept where the type or class of an object is less important than the methods or operations it supports. "If it walks like a duck and quacks like a duck, it’s a duck."

30. What are Python's popular frameworks?
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Ans. Popular frameworks include:

  • Django – High-level web framework
  • Flask – Lightweight web framework
  • FastAPI – Fast modern API framework
  • NumPy / Pandas – Data manipulation
  • TensorFlow / PyTorch – Machine learning
31. What is the purpose of the zip() function?
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Ans. The zip() function combines elements from multiple iterables into tuples.

list(zip([1, 2], ['a', 'b']))  # [(1, 'a'), (2, 'b')]
32. What is the difference between append() and extend()?
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Ans. append() adds a single element to the end of a list, while extend() adds multiple elements.

33. What is a Python virtual environment?
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Ans. A virtual environment is an isolated Python environment that allows different projects to use different dependencies.

34. What are Python's boolean operators?
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Ans. Python has three boolean operators: and, or, and not.

35. What is recursion in Python?
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Ans. Recursion is a process where a function calls itself. Useful for problems like factorial, Fibonacci, etc.

36. How does Python handle type conversion?
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Ans. Python provides implicit and explicit type conversion using functions like int(), str(), float(), etc.

37. What is the difference between @staticmethod and @classmethod?
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Ans. @staticmethod doesn’t take class or instance as the first argument. @classmethod takes cls as the first parameter and can access class-level data.

38. How do you reverse a list in Python?
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Ans. You can use list.reverse() method or slicing list[::-1].

39. What are Python's string methods?
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Ans. Common string methods include upper(), lower(), strip(), split(), join(), replace(), and find().

40. What are Python's logical operators?
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Ans. Logical operators include and, or, and not.

41. What is the use of the enumerate() function?
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Ans. enumerate() adds a counter to an iterable and returns it as an enumerate object.

42. How do you handle exceptions for multiple errors?
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Ans. Use multiple except blocks or a tuple of exceptions in one block.

43. What are Python's bitwise operators?
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Ans. Bitwise operators include &, |, ^, ~, <<, and >>.

44. What is a Python dictionary comprehension?
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Ans. A concise way to create dictionaries.

{x: x**2 for x in range(3)}
45. What is the purpose of the __name__ == "__main__" check?
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Ans. It checks whether the script is run directly or imported as a module.

46. What are generators and iterators?
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Ans. Generators use yield, creating iterators that are memory efficient. Iterators use __iter__() and __next__().

47. What is the map() function?
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Ans. map() applies a function to all items in an iterable.

48. What is the filter() function?
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Ans. filter() filters elements based on a function that returns true or false.

49. What is the reduce() function?
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Ans. reduce() is used to apply a function cumulatively to items (from functools).

50. How do you sort a list of tuples by the second element?
Show Answer

Ans. Use sorted(list_of_tuples, key=lambda x: x[1])

51. What is the GIL (Global Interpreter Lock)?
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Ans. GIL is a mutex that protects access to Python objects, allowing only one thread to execute at a time in CPython.

52. What is the difference between split() and rsplit()?
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Ans. split() splits from the left, rsplit() splits from the right.

53. How can you make a class iterable?
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Ans. Implement __iter__() and __next__() methods.

54. What is a metaclass in Python?
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Ans. A metaclass is a class of a class that defines how classes behave.

55. How is Python code compiled and interpreted?
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Ans. Python code is compiled into bytecode (.pyc), which is then interpreted by the Python virtual machine.

56. What is monkey patching in Python?
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Ans. Monkey patching refers to modifying or extending code at runtime.

57. How do you create custom exceptions?
Show Answer

Ans. Inherit from the base Exception class.

class MyError(Exception):
    pass
58. What are Python's data analysis libraries?
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Ans. Popular libraries include Pandas, NumPy, Matplotlib, and SciPy.

59. What are Python's testing frameworks?
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Ans. Popular testing frameworks include unittest, pytest, and nose.

60. How do you serialize and deserialize data in Python?
Show Answer

Ans. Use the pickle or json module for serialization and deserialization.

import json
data = json.dumps({"name": "Alice"})
obj = json.loads(data)
61. What is list comprehension in Python?
Show Answer

Ans. A concise way to create lists using a single line of code.

[x for x in range(5)]  # [0, 1, 2, 3, 4]
62. What is the difference between deep copy and shallow copy?
Show Answer

Ans. A shallow copy copies references, while a deep copy creates a new copy of the objects.

63. What is duck typing in Python?
Show Answer

Ans. It’s a concept where the type or class of an object is less important than the methods it defines ("If it walks like a duck...").

64. What is the use of the any() and all() functions?
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Ans. any() returns True if any element is True, all() returns True if all elements are True.

65. What is a lambda function?
Show Answer

Ans. A small anonymous function defined using the lambda keyword.

square = lambda x: x * x
66. How do you handle file operations in Python?
Show Answer

Ans. Use the built-in open() function with modes like 'r', 'w', 'a', and 'b'.

67. What is a context manager in Python?
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Ans. An object that properly manages resources using __enter__() and __exit__() methods, often used with with statements.

68. What is the difference between is and ==?
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Ans. is checks identity (same object), == checks equality (same value).

69. What are Python's built-in data types?
Show Answer

Ans. Common types include int, float, str, list, tuple, set, dict, and bool.

70. How do you install packages in Python?
Show Answer

Ans. Use pip install package-name.

71. What is the use of args and kwargs?
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Ans. *args allows variable number of positional arguments, **kwargs allows variable keyword arguments.

72. What is method overloading in Python?
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Ans. Python does not support traditional method overloading. You can achieve similar behavior using default arguments or *args.

73. What is method overriding?
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Ans. When a subclass provides a specific implementation of a method in its parent class.

74. How can you improve performance in Python?
Show Answer

Ans. Use efficient algorithms, built-in functions, libraries like NumPy, and avoid unnecessary computations.

75. What is the difference between a module and a package?
Show Answer

Ans. A module is a single file; a package is a directory with an __init__.py file containing multiple modules.

76. What is a Python decorator?
Show Answer

Ans. A function that takes another function and extends its behavior without modifying it directly.

77. How does Python manage memory?
Show Answer

Ans. Python uses a private heap space and garbage collection to manage memory.

78. What is the collections module?
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Ans. A module that implements specialized container datatypes like Counter, defaultdict, namedtuple, etc.

79. What is a namedtuple?
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Ans. A subclass of tuple with named fields for better readability and access by name.

80. What are Python's type hinting features?
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Ans. Python allows you to specify variable and function types using annotations for better readability and tooling support.

def greet(name: str) -> str:
81. What is the purpose of the os module?
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Ans. The os module provides a way to interact with the operating system, such as file and directory manipulation.

82. How can you list all files in a directory using Python?
Show Answer

Ans. Use os.listdir() or glob.glob().

import os
os.listdir('.')  # lists files in current directory
83. What is the difference between range() and xrange()?
Show Answer

Ans. In Python 2, xrange() is a generator and more memory efficient. In Python 3, only range() exists and behaves like xrange().

84. What is the purpose of with statement?
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Ans. It simplifies resource management, automatically handling setup and teardown (e.g., file operations).

85. What is the assert statement?
Show Answer

Ans. assert is used for debugging to test if a condition is true. Raises AssertionError if the condition is false.

86. What is the difference between int and float in Python?
Show Answer

Ans. int represents whole numbers, float represents numbers with decimal points.

87. How do you convert a string to a number in Python?
Show Answer

Ans. Use int() for integers and float() for floating-point numbers.

88. What is the use of re module?
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Ans. The re module is used for working with regular expressions for pattern matching.

89. What are Python's scopes?
Show Answer

Ans. Python uses the LEGB rule: Local, Enclosing, Global, and Built-in scopes.

90. What is a Python closure?
Show Answer

Ans. A closure is a function object that remembers values in enclosing scopes even if they are not in memory.

91. What are Python’s memory management techniques?
Show Answer

Ans. Python uses reference counting and garbage collection to manage memory.

92. What is the difference between pop() and remove()?
Show Answer

Ans. pop() removes an element at a specific index and returns it. remove() removes the first occurrence of a value.

93. What is slicing in Python?
Show Answer

Ans. Slicing allows extracting parts of sequences using the syntax sequence[start:stop:step].

94. What is the time module used for?
Show Answer

Ans. It provides functions for working with time, such as sleep(), time(), and ctime().

95. What are Python's numeric types?
Show Answer

Ans. int, float, and complex are the three built-in numeric types.

96. What is the __init__.py file?
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Ans. It is used to mark a directory as a Python package. It can also contain initialization code.

97. What is the pass statement?
Show Answer

Ans. pass is a placeholder for future code, used where syntactically some code is required but nothing is needed.

98. What are Python's comparison operators?
Show Answer

Ans. ==, !=, <, >, <=, >=.

99. What is a Python wheel?
Show Answer

Ans. A wheel (.whl) is a built package format for Python that allows faster installation than source distributions.

100. What is the purpose of __str__() and __repr__()?
Show Answer

Ans. __str__() defines the human-readable string for an object, while __repr__() defines the official string representation used for debugging.

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