`contextlib`

Helpers for building, composing, and customising context managers. The decorator @contextmanager adapts a generator into a sync manager; @asynccontextmanager does the same for async generators.

Source-of-record: Lib/contextlib.py, contextlib docs.

Decorators

Decorator	Adapts
`@contextmanager`	A generator yielding once.
`@asynccontextmanager`	An async generator yielding once.

The generator yields the resource. Exceptions thrown into the generator on exit propagate through, unless the generator catches them and exits normally.

Helpers

Helper	Role
`closing(thing)`	Calls `thing.close()` on exit.
`aclosing(thing)`	Awaits `thing.aclose()` on exit.
`suppress(*exceptions)`	Swallow the listed exceptions.
`redirect_stdout(target)`	Patch `sys.stdout` for the block.
`redirect_stderr(target)`	Patch `sys.stderr` for the block.
`nullcontext(enter_result=None)`	No-op manager; useful as a placeholder.
`chdir(path)`	Change cwd for the block.

Stacks

Class	Variant	Use
`ExitStack`	sync	Dynamic composition; LIFO unwinding.
`AsyncExitStack`	async	Mix of sync and async managers.

ExitStack methods:

Method	Behaviour
`enter_context(cm)`	Enter `cm` and record it.
`push(cm_or_exit)`	Record an existing exit callback.
`callback(fn, args, *kw)`	Record a plain function to call.
`pop_all()`	Transfer callbacks to a fresh stack.
`close()`	Run all callbacks.

AsyncExitStack adds enter_async_context, push_async_exit, push_async_callback, aclose.

Base classes

Class	Implements
`ContextDecorator`	Mix-in: lets a manager double as a decorator.
`AsyncContextDecorator`	Same, for async.
`AbstractContextManager`	ABC with `__enter__` and `__exit__`.
`AbstractAsyncContextManager`	ABC with `__aenter__` and `__aexit__`.

Suppress patterns

with suppress(FileNotFoundError):
    os.remove(path)

suppress catches subclass exceptions matching any of the listed types and continues. Behaves like try/except: pass.

Gopy status

Area	State
`@contextmanager`, `@asynccontextmanager`	Complete.
`closing`, `aclosing`, `suppress`, redirects, `nullcontext`, `chdir`	Complete.
`ExitStack`, `AsyncExitStack`	Complete.
ABCs	Complete.

Reference

CPython 3.14: contextlib.
Lib/contextlib.py.
module/contextlib/. gopy port.

Decorators​

Helpers​

Stacks​

Base classes​

Suppress patterns​

Gopy status​

Reference​