What are decorators in Python?

ICSM Computer 616 22 Apr 2025

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Updated 02 Jun 2025

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ICSM Computer 02 Jun 2025

Decorators in Python are a powerful and elegant way to modify or enhance the behavior of functions or methods without changing their actual code.

What is a decorator?

A decorator is essentially a function that takes another function as input and returns a new function that adds some kind of functionality before or after the original function runs.
You apply decorators using the @decorator_name syntax placed just above the function definition.

Why use decorators?

To add reusable functionality (e.g., logging, timing, access control) to many functions without repeating code.
To keep your code clean and separate concerns.

Basic example of a decorator

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!")

say_hello()

Output:

Before the function runs
Hello!
After the function runs

How it works:

@my_decorator is syntactic sugar for:

say_hello = my_decorator(say_hello)

When you call say_hello(), it actually calls wrapper(), which runs extra code around the original function.

Decorators with arguments

To decorate functions that take parameters, your wrapper function should accept *args and **kwargs:

def decorator(func):
    def wrapper(*args, **kwargs):
        print("Before")
        result = func(*args, **kwargs)
        print("After")
        return result
    return wrapper

@decorator
def greet(name):
    print(f"Hello, {name}!")

greet("Alice")

Summary

Decorators wrap a function to extend its behavior.
They’re commonly used for logging, memoization, access control, performance measurement, etc.
Python includes built-in decorators like @staticmethod, @classmethod, and @property.

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What are decorators in Python?

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1 Answers

What is a decorator?

Why use decorators?

Basic example of a decorator

How it works:

Decorators with arguments

Summary