Python Decorators — Add Superpowers to Your Functions

What Are Decorators?

Decorators are functions that modify other functions. They use the @decorator syntax for a clean, readable way to add functionality.

Basic Decorator

from functools import wraps

def my_decorator(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        print("Before function")
        result = func(*args, **kwargs)
        print("After function")
        return result
    return wrapper

@my_decorator
def say_hello(name):
    print(f"Hello, {name}!")

Timing Decorator

import time
from functools import wraps

def timer(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        start = time.perf_counter()
        result = func(*args, **kwargs)
        elapsed = time.perf_counter() - start
        print(f"{func.__name__} took {elapsed:.4f}s")
        return result
    return wrapper

Retry Decorator

def retry(max_attempts=3, delay=1):
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            for attempt in range(max_attempts):
                try:
                    return func(*args, **kwargs)
                except Exception as e:
                    if attempt == max_attempts - 1:
                        raise
                    time.sleep(delay * (2 ** attempt))
        return wrapper
    return decorator

@retry(max_attempts=3)
def fetch_data(url):
    return requests.get(url).json()

Built-in Decorators

class Circle:
    def __init__(self, radius):
        self._radius = radius
    
    @property
    def radius(self):
        return self._radius
    
    @staticmethod
    def from_diameter(diameter):
        return Circle(diameter / 2)
    
    @classmethod
    def unit_circle(cls):
        return cls(1)