You can combine `dataclasses` with other type annotations in many different combinations to form complex data structures.

Check the in-code annotation tips above to see more specific details.

## Learn More

You can also combine `dataclasses` with other Pydantic models, inherit from them, include them in your own models, etc.

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.

| `license_info` | `dict` | The license information for the exposed API. It can contain several fields. <details><summary><code>license_info</code> fields</summary><table><thead><tr><th>Parameter</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td><code>name</code></td><td><code>str</c...

</div>

That would work for most of the cases. 😎

You could use that command for example to start your **FastAPI** app in a container, in a server, etc.

## ASGI Servers

Let's go a little deeper into the details.

FastAPI uses a standard for building Python web frameworks and servers called <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr>. FastAPI is an ASGI web framework.

```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.

Und dann schreibt ein weiterer Hintergrundtask, der in der *Pfadoperation-Funktion* erstellt wird, eine Nachricht unter Verwendung des Pfad-Parameters `email`.

## Technische Details

Die Klasse `BackgroundTasks` stammt direkt von <a href="https://www.starlette.io/background/" class="external-link" target="_blank">`starlette.background`</a>.

!!! tip "Подсказка"
    Торопитесь или уже знакомы с этой технологией? Перепрыгните на раздел [Создать Docker-образ для FastAPI 👇](#docker-fastapi)

<details>
<summary>Развернуть Dockerfile 👀</summary>

```Dockerfile
FROM python:3.9

WORKDIR /code

COPY ./requirements.txt /code/requirements.txt

<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.

@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>O usa <code>async def</code>...</summary>

Si tu código usa `async` / `await`, usa `async def`:

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