///

Abhängigkeiten mit `yield` haben sich im Laufe der Zeit weiterentwickelt, um verschiedene Anwendungsfälle abzudecken und einige Probleme zu beheben, hier ist eine Zusammenfassung der Änderungen.

### Abhängigkeiten mit `yield` und `scope` { #dependencies-with-yield-and-scope }

Подробнее читайте в документации: [Зависимости с `yield` — раннее завершение и `scope`](../tutorial/dependencies/dependencies-with-yield.md#early-exit-and-scope).

### Зависимости с `yield` и `StreamingResponse`, технические детали { #dependencies-with-yield-and-streamingresponse-technical-details }

///

Dependências com `yield` evoluíram ao longo do tempo para contemplar diferentes casos de uso e corrigir alguns problemas, aqui está um resumo do que mudou.

### Dependências com `yield` e `scope` { #dependencies-with-yield-and-scope }

Na versão 0.121.0, o FastAPI adicionou suporte a `Depends(scope="function")` para dependências com `yield`.

            if self.open:
                yield item
            else:
                raise ValueError("Session closed")


@contextmanager
def acquire_session() -> Generator[Session, None, None]:
    session = Session()
    try:
        yield session
    finally:
        session.open = False


def dep_session() -> Any:
    with acquire_session() as s:
        yield s


def broken_dep_session() -> Any:

			}
			if !yield(line[:len(line):len(line)]) {
				return
			}
		}
	}
}

// splitSeq is SplitSeq or SplitAfterSeq, configured by how many
// bytes of sep to include in the results (none or all).
func splitSeq(s, sep []byte, sepSave int) iter.Seq[[]byte] {
	return func(yield func([]byte) bool) {
		if len(sep) == 0 {
			for len(s) > 0 {
				_, size := utf8.DecodeRune(s)
				if !yield(s[:size:size]) {
					return

    async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    @asynccontextmanager
    async def router_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"router": True}

    @asynccontextmanager
    async def sub_router_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    sub_router = APIRouter(lifespan=sub_router_lifespan)

            async for item in iterate_in_threadpool(func(*args, **kwargs)):
                yield item

        return gen_wrapper

    elif inspect.isasyncgenfunction(func):

        @wraps(func)
        async def async_gen_wrapper(*args, **kwargs):
            async for item in func(*args, **kwargs):
                yield item

        return async_gen_wrapper

    @wraps(func)

class Session:
    def __init__(self) -> None:
        self.open = True


def dep_session() -> Any:
    s = Session()
    yield s
    s.open = False


def raise_after_yield() -> Any:
    yield
    raise HTTPException(status_code=503, detail="Exception after yield")


SessionFuncDep = Annotated[Session, Depends(dep_session, scope="function")]

from fastapi import Depends


async def dependency_a():
    dep_a = generate_dep_a()
    try:
        yield dep_a
    finally:
        dep_a.close()


async def dependency_b(dep_a: Annotated[DepA, Depends(dependency_a)]):
    dep_b = generate_dep_b()
    try:
        yield dep_b
    finally:
        dep_b.close(dep_a)


async def dependency_c(dep_b: Annotated[DepB, Depends(dependency_b)]):

Lo primero que hay que notar es que estamos definiendo una función asíncrona con `yield`. Esto es muy similar a las Dependencias con `yield`.

{* ../../docs_src/events/tutorial003_py39.py hl[14:19] *}

La primera parte de la función, antes del `yield`, será ejecutada **antes** de que la aplicación comience.

Y la parte después del `yield` será ejecutada **después** de que la aplicación haya terminado.