decorator

id	structural/decorator
name	Decorator
aliases	wrapper
guide_url	https://python-patterns.guide/gang-of-four/decorator-pattern/
problem	Add behavior around an object or callable without editing it or subclassing it.
symptoms	logging every call caching results retry wrapper timing calls add behavior without subclassing
verdict	pythonic
caveats	The GoF pattern (wrapping objects) and Python's @decorator syntax (wrapping callables) are cousins, not the same thing — this unit shows both. Always apply functools.wraps to function wrappers, or you destroy the wrapped function's name, docstring, and introspection. The guide's caveat: an object wrapper doesn't survive isinstance checks or identity comparisons — wrapping doesn't actually make you the wrapped thing.
stdlib_sightings	functools.wraps functools.lru_cache contextlib.contextmanager

Decorator

Add one cross-cutting concern at a time — logging, timing, retries, limits — by wrapping, then stack the wrappers. Verdict: pythonic — for callables the language absorbed the pattern into @decorator syntax.

Where	What
pattern/	The importable code: logged, timed, retry, rate_limited
docs/	Fundamentals · Implementation guide · External examples
examples/resilient_client/	Mini-project: a flaky API client hardened by stacking pattern/ decorators
tests/	Behavioral tests for the pattern and the mini-project

uv run python -m patterns.structural.decorator.examples.resilient_client.main