What are Python decorators?

Decorators let you add functionality — like logging, timing, or access checks — around an existing function in a clean, reusable way.

A simple 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!")

say_hello()

Calling say_hello() now runs the wrapper function, which prints a message, runs the original function, and prints another message — all without changing the original say_hello function's code.

Common real-world uses

• Logging how long a function takes to run
• Checking whether a user is authenticated before allowing a function to run (common in web frameworks like Flask and Django)
• Caching a function's results so repeated calls with the same input skip recomputation