Have you used decorators in Python? What is their use?

Decorators in Python are a syntactic convenience that allows you to modify or extend the behavior of functions or classes without changing their code. A decorator is a callable that takes a function (or class) as an argument and returns a new function (or class). The @decorator syntax is shorthand for assigning the result of the decorator to the original name. Common use cases include logging, authentication, caching, and input validation. For example, a simple timing decorator can measure execution time:

import time

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

@timer
def compute(x):
    return sum(i for i in range(x))

When compute is called, the wrapper runs first, timing the call and then invoking the original function. Decorators can also be parameterized by returning a decorator factory. They promote code reuse, separation of concerns, and cleaner APIs. Understanding how to write and apply decorators is essential for advanced Python development, especially in frameworks like Flask or Django where decorators are used for routing, authentication, and middleware.