```Python
with open("file.txt") as file:
    file.read()
```

最近の Python には「非同期コンテキストマネージャ」もあります。`async with` で使います:

```Python
async with lifespan(app):
    await do_stuff()
```

このようにコンテキストマネージャ（または非同期コンテキストマネージャ）を作ると、`with` ブロックに入る前に `yield` より前のコードが実行され、`with` ブロックを出た後に `yield` より後ろのコードが実行されます。

上のコード例では直接それを使ってはいませんが、FastAPI に渡して内部で使ってもらいます。

./mc rm -r --force myminio/versioned >/dev/null

## mirror again to create another set of version on top
./mc mirror internal myminio/versioned/ --quiet >/dev/null

expected_checksum=$(./mc cat internal/dsync/drwmutex.go | md5sum)

user_count=$(./mc admin user list myminio/ | wc -l)
policy_count=$(./mc admin policy list myminio/ | wc -l)

kill $pid

golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

	exit 1
fi

got_checksum=$(./mc cat myminio/versioned/dsync/drwmutex.go | md5sum)
if [ "${expected_checksum}" != "${got_checksum}" ]; then
	echo "BUG: decommission failed on encrypted objects: expected ${expected_checksum} got ${got_checksum}"
	exit 1
fi

got_checksum_1=$(./mc cat myminio/versioned-1/dsync/drwmutex.go | md5sum)
if [ "${expected_checksum}" != "${got_checksum_1}" ]; then

///

### Funções de operação de rota não assíncronas { #non-async-path-operation-functions }

Você também pode usar funções `def` normais (sem `async`) e usar `yield` da mesma forma.

O FastAPI garantirá que sejam executadas corretamente para não bloquear o event loop.

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: str | None = Query(default=None, min_length=3, max_length=50)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from fastapi import FastAPI, HTTPException

app = FastAPI()

items = {"foo": "The Foo Wrestlers"}


@app.get("/items/{item_id}")
async def read_item(item_id: str):
    if item_id not in items:
        raise HTTPException(status_code=404, detail="Item not found")

from fastapi import FastAPI, Path

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(*, item_id: int = Path(title="The ID of the item to get"), q: str):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str, Query(min_length=3)] = "fixedquery"):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

class JsonApiError(BaseModel):
    errors: list[Error]


@app.get(
    "/a/{id}",
    response_class=JsonApiResponse,
    responses={422: {"description": "Error", "model": JsonApiError}},
)
async def a(id):
    pass  # pragma: no cover


client = TestClient(app)


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text