The generator runs once: code before yield is the __enter__ body, the yielded object is bound by as, and code after yield is the __exit__ body. Wrapping the post-yield code in try / finally is mandatory when teardown must run on exceptions too: without it, an exception from the body skips the cleanup. The decorator handles the boilerplate of building a class with __enter__ and __exit__, so the implementation reads top-to-bottom like normal code. Use this pattern for stateless, run-once setup-and-teardown helpers.

The try / except / else / finally shape inside a @contextmanager mirrors what a class-based __exit__ lets you express, but reads more linearly. The except branch fires only when the body raised, else only when it did not, and finally always. Re-raising with a bare raise is the way to log AND let the caller decide what to do; swallowing here would behave like returning True from __exit__. This is the standard shape for instrumentation: timers, audit logs, span starts and ends.

contextlib.suppress(*excs) replaces the boilerplate try / except: pass block when you genuinely do not care about a specific failure. ExitStack is the answer to 'I need N context managers but N is computed at runtime': call stack.enter_context(cm) once per resource and the stack guarantees they all close in LIFO order on exit. Together with @contextmanager, these three tools cover almost every 'I want a custom with-block' use case without writing a class at all.