async def context_a(state: dict = Depends(get_state)):
    state["context_a"] = "started a"
    try:
        yield state
    finally:
        state["context_a"] = "finished a"


async def context_b(state: dict = Depends(context_a)):
    state["context_b"] = "started b"
    try:
        yield state
    finally:
        state["context_b"] = f"finished b with a: {state['context_a']}"

/// tip | Dica

Outra forma de criar um gerenciador de contexto é utilizando:

* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.contextmanager" class="external-link" target="_blank">`@contextlib.contextmanager`</a> ou
* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager" class="external-link" target="_blank">`@contextlib.asynccontextmanager`</a>

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

Em versões mais recentes do Python, há também um **gerenciador de contexto assíncrono**. Você o usaria com `async with`:

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

from collections.abc import AsyncGenerator
from contextlib import AbstractContextManager
from contextlib import asynccontextmanager as asynccontextmanager
from typing import TypeVar

import anyio.to_thread
from anyio import CapacityLimiter
from starlette.concurrency import iterate_in_threadpool as iterate_in_threadpool  # noqa
from starlette.concurrency import run_in_threadpool as run_in_threadpool  # noqa
from starlette.concurrency import (  # noqa

/// tip | Consejo

Otra manera de crear un context manager es con:

* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.contextmanager" class="external-link" target="_blank">`@contextlib.contextmanager`</a> o
* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager" class="external-link" target="_blank">`@contextlib.asynccontextmanager`</a>

/// tip

Another way to create a context manager is with:

* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.contextmanager" class="external-link" target="_blank">`@contextlib.contextmanager`</a> or
* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager" class="external-link" target="_blank">`@contextlib.asynccontextmanager`</a>

* «/// tip»: «/// tip | Dica»
* «/// warning»: «/// warning | Atenção»
* «(you should)»: «(você deveria)»
* async context manager: gerenciador de contexto assíncrono
* autocomplete: autocompletar
* autocompletion: preenchimento automático
* bug: bug
* context manager: gerenciador de contexto
* cross domain: cross domain (do not translate to "domínio cruzado")
* cross origin: cross origin (do not translate to "origem cruzada")

import asyncio
from contextlib import asynccontextmanager
from unittest.mock import Mock, patch

from docs_src.dependencies.tutorial007_py39 import get_db


def test_get_db():  # Just for coverage
    async def test_async_gen():
        cm = asynccontextmanager(get_db)
        async with cm() as db_session:
            return db_session

    dbsession_moock = Mock()

    with patch(

Любая функция, с которой можно корректно использовать:

* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.contextmanager" class="external-link" target="_blank">`@contextlib.contextmanager`</a> или
* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager" class="external-link" target="_blank">`@contextlib.asynccontextmanager`</a>

будет корректной для использования в качестве зависимости **FastAPI**.

Jede Funktion, die dekoriert werden kann mit:

* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.contextmanager" class="external-link" target="_blank">`@contextlib.contextmanager`</a> oder
* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager" class="external-link" target="_blank">`@contextlib.asynccontextmanager`</a>

kann auch als gültige **FastAPI**-Abhängigkeit verwendet werden.