它将函数转化为所谓的“**异步上下文管理器**”。

{* ../../docs_src/events/tutorial003_py310.py hl[1,13] *}

在 Python 中，**上下文管理器**是一个你可以在 `with` 语句中使用的东西，例如，`open()` 可以作为上下文管理器使用。

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

Python 的最近几个版本也有了一个**异步上下文管理器**，你可以通过 `async with` 来使用：

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

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