Top 10 Essential Python Interview Questions and Answers

Sure! Below are ten essential Python interview questions along with their answers:

1. What is Python, and what are its key features?
   Answer:
   Python is a high-level, interpreted programming language known for its simplicity and readability. Key features include dynamic typing, automatic memory management (garbage collection), extensive standard libraries, and support for multiple programming paradigms (procedural, object-oriented, functional).
2. What is the difference between Python 2 and Python 3?
   Answer:
   Python 2 and Python 3 are two major versions of Python. Python 3 introduced several backward-incompatible changes, including print function syntax, Unicode as the default string type, and the use of “xrange” becoming “range.” Python 2 is no longer being developed and supported, so it’s recommended to use Python 3 for all new projects.
3. Explain Python decorators
   Answer:
   Python decorators are functions that modify the behavior of other functions. They allow you to wrap another function, adding functionality before or after the wrapped function’s execution. Decorators are denoted by the “@” symbol in Python. For example:

def my_decorator(func):
    def wrapper(*args, **kwargs):
        print("Something is happening before the function is called.")
        result = func(*args, **kwargs)
        print("Something is happening after the function is called.")
        return result
    return wrapper

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

say_hello()

4. What is the Global Interpreter Lock (GIL) in Python?
Answer:
The Global Interpreter Lock (GIL) is a mutex used in CPython (the standard implementation of Python) to prevent multiple native threads from executing Python bytecodes at once. It means that even on multi-core processors, Python threads can’t utilize multiple cores simultaneously for CPU-bound tasks. However, it does not prevent threading for I/O-bound tasks, as I/O operations release the GIL.

5. How do you handle exceptions in Python?
Answer:
Python provides a try-except block to handle exceptions. The code that may raise an exception is placed within the try block, and the exception handling logic is defined in the except block. For example:

try:
    result = x / y
except ZeroDivisionError:
    print("Error: Division by zero!")
except Exception as e:
    print(f"An error occurred: {e}")
else:
    print(f"The result is: {result}")
finally:
    print("This will always execute.")

6. Explain the difference between “deep copy” and “shallow copy” in Python.
Answer:
In Python, a “shallow copy” creates a new object but inserts references to the original elements. A “deep copy,” on the other hand, creates a new object and recursively copies all objects it references. To make shallow and deep copies, you can use the copy module:

import copy

original_list = [1, [2, 3], 4]
shallow_copy = copy.copy(original_list)
deep_copy = copy.deepcopy(original_list)

7. What are lambda functions in Python?
Answer:
Lambda functions, also known as anonymous functions, are small, one-line functions defined without a name. They are created using the lambda keyword and are useful for simple, throwaway functions. Lambda functions can take any number of arguments but can only have one expression. For example:

add = lambda x, y: x + y
print(add(3, 5))  # Output: 8

8. How do you handle file I/O in Python?
Answer:
Python provides built-in functions for file I/O operations. To read from a file:

with open("file.txt", "r") as file:
    content = file.read()

To write to a file:

with open("file.txt", "w") as file:
    file.write("Hello, this is some content.")

9. Explain the use of the __init__ method in Python classes.
Answer:
The __init__ method is a special method in Python classes, called when an object is created. It is used to initialize object attributes and perform any necessary setup. For example:

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

obj = MyClass("John")

10. How do you handle modules in Python?
Answer:
In Python, a module is a file containing Python definitions and statements. To use a module, you can import it using the import keyword. For example:

# Import the whole module
import math
print(math.sqrt(16))  # Output: 4.0

# Import specific items from a module
from datetime import date
today = date.today()
print(today)  # Output: YYYY-MM-DD

These questions cover various essential aspects of Python and should help you prepare for your Python interview. Remember to also practice coding and working with Python to gain hands-on experience. Good luck!