@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Albo użyj <code>async def</code>...</summary>

Jeżeli twój kod korzysta z `async` / `await`, użyj `async def`:

```Python hl_lines="9  14"
from typing import Union

@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Или используйте <code>async def</code>...</summary>

Если ваш код использует `async` / `await`, используйте `async def`:

```Python hl_lines="9  14"
from typing import Union

@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: str = Optional[None]):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Oppure usa <code>async def</code>...</summary>

Se il tuo codice usa `async` / `await`, allora usa `async def`:

```Python hl_lines="7  12"
from fastapi import FastAPI

INFO:     Application startup complete.
```

</div>

<details markdown="1">
<summary>关于 <code>uvicorn main:app --reload</code> 命令......</summary>

 `uvicorn main:app` 命令含义如下:

* `main`：`main.py` 文件（一个 Python "模块"）。
* `app`：在 `main.py` 文件中通过 `app = FastAPI()` 创建的对象。
* `--reload`：让服务器在更新代码后重新启动。仅在开发时使用该选项。

</details>

### 检查

It was one of the first extremely fast Python frameworks based on `asyncio`. It was made to be very similar to Flask.

!!! note "Technical Details"
    It used <a href="https://github.com/MagicStack/uvloop" class="external-link" target="_blank">`uvloop`</a> instead of the default Python `asyncio` loop. That's what made it so fast.

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI` ist eine Python-Klasse, die die gesamte Funktionalität für Ihre API bereitstellt.

!!! note "Technische Details"
    `FastAPI`  ist eine Klasse, die direkt von `Starlette` erbt.

    Sie können alle <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a>-Funktionalitäten auch mit `FastAPI` nutzen.

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

If you use Hypercorn, it also has the option `--root-path`.

!!! note "Technical Details"
    The ASGI specification defines a `root_path` for this use case.

    And the `--root-path` command line option provides that `root_path`.

### Checking the current `root_path`

### Step 1: import `FastAPI`

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI` is a Python class that provides all the functionality for your API.

!!! note "Technical Details"
    `FastAPI` is a class that inherits directly from `Starlette`.

    You can use all the <a href="https://www.starlette.io/" class="external-link" target="_blank">Starlette</a> functionality with `FastAPI` too.

That way, you don't have to "install" your local version to be able to test every change.

!!! note "Technical Details"
    This only happens when you install using this included `requirements.txt` instead of running `pip install fastapi` directly.

```

!!! info
    如果您需要异步连接到关系数据库，请参阅[Async SQL (Relational) Databases](https://fastapi.tiangolo.com/zh/advanced/async-sql-databases/)

!!! note "Very Technical Details"
    如果您很好奇并且拥有深厚的技术知识，您可以在[Async](https://fastapi.tiangolo.com/zh/async/#very-technical-details)文档中查看有关如何处理 `async def`于`def`差别的技术细节。

## 迁移

因为我们直接使用 SQLAlchemy，并且我们不需要任何类型的插件来使用**FastAPI**，所以我们可以直接将数据库迁移至[Alembic](https://alembic.sqlalchemy.org/)进行集成。