examples.md

Decorator — where it lives outside this repo

Cited, real implementations to study (or point an agent at) when designing or reviewing decorator-shaped code.

Python standard library

• functools.lru_cache / functools.cache. Memoization as a decorator — wrap a function, gain a cache and cache_info() statistics. The pattern shipping in the box. docs.python.org/3/library/functools.html#functools.lru_cache
• functools.wraps. A decorator whose only job is making other decorators honest — it copies the wrapped function's identity onto the wrapper. docs.python.org/3/library/functools.html#functools.wraps
• contextlib.contextmanager. Wraps a generator into a context manager — a decorator that changes the kind of the thing it wraps. docs.python.org/3/library/contextlib.html#contextlib.contextmanager

Major ecosystems

• Flask routing. @app.route("/path") registers view functions into the URL map at definition site — decorator as registration API. flask.palletsprojects.com/en/stable/quickstart/#routing
• Django's @login_required. Access control layered onto views without touching them. docs.djangoproject.com/en/stable/topics/auth/default/#the-login-required-decorator
• tenacity. Production retry policies (backoff, jitter, stop conditions) stacked onto callables — this unit's retry grown up. tenacity.readthedocs.io
• click. Whole CLIs built by stacking @click.command and @click.option — decorators composing a program's surface. click.palletsprojects.com

What to notice across all of them

Every one preserves the wrapped callable's contract (arguments in, result out) and adds exactly one concern beside it. And every serious one calls functools.wraps — check for it first when reviewing any hand-rolled decorator.