Python decorators — from @property to writing your own_

A decorator is a function that takes a function and returns a function. @my_decorator above def foo() is exactly equivalent to foo = my_decorator(foo). Once that clicks, all decorator syntax follows. Start by writing one without the @ sugar.

When you write a decorator, always apply @functools.wraps(func) to your inner wrapper function. Without it, the wrapped function loses its __name__, __doc__, and signature — which breaks help(), introspection, and some frameworks.

You can use a class as a decorator by implementing __call__. This is useful when the decorator needs to maintain state across calls — for example a rate limiter that counts invocations. The instance is the decorator and each call goes through __call__.

A retry decorator is the canonical real-world example. It wraps a function, catches specified exceptions, waits with exponential backoff, and retries up to N times. Writing it yourself teaches you everything about decorators and is more useful than any tutorial.