Decorator in Python by Vaibhav Singh

What is a Decorator in Python?

A decorator in Python is a function that modifies the behaviour of another function, method, or class, without changing its actual code. It's like putting a filter, wrapper, or enhancer around your function.

Real-Life Analogy

Imagine your function is a plain dosa.

The decorator is the masala filling and chutney you wrap around it.

Same dosa, but now it’s "Masala Dosa Deluxe"

Basic Decorator Example

def my_decorator(func):

def wrapper():

print("Before the function runs")

func()

print("After the function runs")

return wrapper

@my_decorator

def say_hello():

print("Hello, Vaibhav!")

say_hello()

Output:

Before the function runs

Hello, Vaibhav!

After the function runs

The @my_decorator wraps say_hello — without modifying its original logic!

How Decorator Works

@decorator is syntactic sugar for:

say_hello = my_decorator(say_hello)

Decorators use closures (a function inside another function) to wrap and enhance behavior.

Common Use Cases

Use Case	Example Decorator
Logging	`@log`
Timing	`@timeit`
Authorization	`@login_required`
Caching	`@lru_cache` from `functools`
Input validation	`@validate_json`

Decorators with Arguments

def repeat(n):

def decorator(func):

def wrapper(*args, **kwargs):

for _ in range(n):

func(*args, **kwargs)

return wrapper

return decorator

@repeat(3)

def cheer():

print("Python Rocks!")

cheer()

Output:

Python Rocks!

Summary

Decorator Is...	Meaning
A wrapper	Enhances a function without changing its source
Reusable	Can be applied to many functions
Flexible	Can accept arguments
Readable	Makes cross-cutting concerns (logging, auth, etc.) cleaner

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