20 Interview Questions In Python

Python Basics & Core Concepts

1. What are Python’s key features?

Interpreted: No need to compile before execution.
Dynamically Typed: Variable types are inferred.
Object-Oriented & Functional: Supports both paradigms.
Automatic Memory Management: Uses garbage collection.
Extensive Libraries: Includes NumPy, Pandas, Django, etc.

2. How does Python handle memory management?

Python uses:

Garbage Collection (GC): Automatically removes unused objects.
Reference Counting: Objects are deleted when their reference count drops to zero.
Memory Pools: Managed by PyMalloc for small objects.

3. What is the difference between deep copy and shallow copy?

Shallow Copy (copy.copy()): Creates a new object but references nested objects (changes affect original).
Deep Copy (copy.deepcopy()): Recursively copies all objects, ensuring independence.

4. How does Python’s GIL (Global Interpreter Lock) affect multithreading?

The GIL allows only one thread to execute Python bytecode at a time, limiting CPU-bound performance.

Use multiprocessing for CPU-intensive tasks.
Use threading for I/O-bound tasks (file I/O, network calls).

Object-Oriented Programming (OOP)

5. What are Python’s key OOP principles?

Encapsulation: Hiding data using private (_var) and protected (__var) attributes.
Inheritance: Creating child classes from parent classes.
Polymorphism: Implementing methods differently across classes.
Abstraction: Hiding implementation details using abstract base classes (ABC module).

6. Explain method overriding vs. method overloading in Python.

Overriding: Redefining a method in a subclass that exists in the parent class.
Overloading: Python does not support method overloading directly, but can be achieved using default arguments or *args, **kwargs.

class Parent:
    def show(self):
        print("Parent method")

class Child(Parent):
    def show(self):  # Overriding
        print("Child method")

obj = Child()
obj.show()  # Output: Child method

Advanced Python Topics

7. What is the difference between @staticmethod, @classmethod, and instance methods?

Instance Method: Works with self, accesses instance attributes.
Class Method (@classmethod): Works with cls, accesses class variables.
Static Method (@staticmethod): No access to self or cls, behaves like a normal function inside a class.

class Demo:
    class_var = "Class Level"
    
    def instance_method(self):
        return "Instance Method"
    
    @classmethod
    def class_method(cls):
        return cls.class_var
    
    @staticmethod
    def static_method():
        return "Static Method"

print(Demo.class_method())  # Accesses class variable
print(Demo.static_method())  # Acts like a regular function

8. What are metaclasses in Python?

Metaclasses define how classes behave. They allow customizing class creation.
Example:

class Meta(type):
    def __new__(cls, name, bases, dct):
        print(f"Creating class {name}")
        return super().__new__(cls, name, bases, dct)

class MyClass(metaclass=Meta):
    pass
# Output: Creating class MyClass

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

is checks object identity (memory location).
== checks value equality.

a = [1, 2, 3]
b = a
print(a is b)  # True (same object)
print(a == b)  # True (same value)

image credits https://www.freepik.com/

Error Handling & Debugging

10. How does Python handle exceptions?

Python uses try-except-finally blocks for exception handling.
Example:

try:
    x = 10 / 0
except ZeroDivisionError as e:
    print("Cannot divide by zero!")
finally:
    print("Execution complete.")

11. What are Python’s built-in debugging tools?

print(): Simple debugging.
logging: More detailed logs (logging.debug(), logging.error()).
pdb: Python debugger (import pdb; pdb.set_trace()).

File Handling & I/O

12. How do you read and write files in Python?

with open("file.txt", "r") as f:
    data = f.read()  # Read file

with open("file.txt", "w") as f:
    f.write("Hello, World!")  # Write to file

Python Libraries & Frameworks

13. What is the difference between NumPy and Pandas?

NumPy: Efficient numerical computations, supports multi-dimensional arrays.
Pandas: Built on NumPy, provides high-level data manipulation (DataFrames, Series).

14. What is Flask, and how does it compare to Django?

Flask: Lightweight, minimalistic, ideal for small projects and microservices.
Django: Full-featured, follows MTV (Model-Template-View) pattern, best for large applications.

15. How does Python’s multiprocessing module work?

Multiprocessing creates separate processes that run concurrently, bypassing the GIL.
Example:

from multiprocessing import Pool

def square(n):
    return n * n

with Pool(4) as p:
    result = p.map(square, [1, 2, 3, 4])
print(result)  # Output: [1, 4, 9, 16]

Data Structures & Algorithms in Python

16. What are Python’s built-in data structures?

List ([]) – Ordered, mutable, allows duplicates.
Tuple (()) – Ordered, immutable, allows duplicates.
Set ({}) – Unordered, unique elements.
Dictionary ({key: value}) – Key-value pairs.

17. How do you implement a linked list in Python?

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

Testing & Code Quality

18. What are Python’s testing frameworks?

unittest (built-in).
pytest (popular, simple, supports fixtures).
doctest (tests inside docstrings).

Concurrency & Asynchronous Programming

19. What is the difference between threading and asyncio in Python?

Threading: Good for I/O-bound tasks (e.g., file I/O, network).
asyncio: Best for cooperative multitasking (async/await).

Deployment & Performance Optimization

20. How do you optimize Python performance?

Use generators instead of lists.
Use Cython or Numba for computational efficiency.
Use multiprocessing for CPU-bound tasks.
Profile code using cProfile.

Final Thoughts

These questions cover Python basics, OOP, performance optimization, concurrency, testing, and deployment. Do you need role-specific questions, like for web development, data engineering, or AI applications? 🚀
for more details tutorials you can login to my tutorials website in Python www.pythonmates.com

20 Interview Questions in Python

Table of Contents