It has an interesting, uncommon feature: using the same framework, it's possible to create APIs and also CLIs.

As it is based on the previous standard for synchronous Python web frameworks (WSGI), it can't handle Websockets and other things, although it still has high performance too.

!!! info

## Technical Details

Modern versions of Python have support for **"asynchronous code"** using something called **"coroutines"**, with **`async` and `await`** syntax.

Let's see that phrase by parts in the sections below:

* **Asynchronous Code**
* **`async` and `await`**
* **Coroutines**

## Asynchronous Code

!!! tip
    If you want to call `async` functions in your tests apart from sending requests to your FastAPI application (e.g. asynchronous database functions), have a look at the [Async Tests](../advanced/async-tests.md){.internal-link target=_blank} in the advanced tutorial.

## Separating tests

## 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.

    **FastAPI** ⤴️ ✊ 👈 🎻 🔗 💽 & 🚮 ⚫️ 🗄, ↖️ ⚪️➡️ 🌐 🎏 👜 ⚫️ 🔨.

### <a href="https://www.starlette.io/" class="external-link" target="_blank">💃</a>

💃 💿 <abbr title="The new standard for building asynchronous Python web">🔫</abbr> 🛠️/🧰, ❔ 💯 🏗 ↕-🎭 ✳ 🐕‍🦺.

⚫️ 📶 🙅 &amp; 🏋️. ⚫️ 🔧 💪 🏧, &amp; ✔️ 🔧 🦲.

⚫️ ✔️:

* 🤙 🎆 🎭.
*  *️⃣ 🐕‍🦺.
* -🛠️ 🖥 📋.
* 🕴 &amp; 🤫 🎉.
* 💯 👩‍💻 🏗 🔛 🇸🇲.

place, en étant "asynchrone", une fois terminée, une tâche peut légèrement attendre (quelques microsecondes) que l'ordinateur / le programme finisse ce qu'il était en train de faire, et revienne récupérer le résultat.

Pour parler de tâches "synchrones" (en opposition à "asynchrones"), on utilise souvent le terme "séquentiel", car l'ordinateur / le programme va effectuer toutes les étapes d'une tâche séquentiellement avant de passer à une autre tâche, même si ces étapes impliquent de l'attente....

# 並行処理と async / await

*path operation 関数*のための `async def` に関する詳細と非同期 (asynchronous) コード、並行処理 (Concurrency)、そして、並列処理 (Parallelism) の背景について。

## 急いでいますか？

<abbr title="too long; didn't read (長すぎて読めない人のための要約という意味のスラング)"><strong>TL;DR:</strong></abbr>

次のような、`await` を使用して呼び出すべきサードパーティライブラリを使用している場合:

```Python
results = await some_library()
```

以下の様に `async def` を使用して*path operation 関数*を宣言します。

```Python hl_lines="2"
@app.get('/')

Here's a little bit of that history.

## Alternatives

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

As part of that, I needed to investigate, test and use many alternatives.

The history of **FastAPI** is in great part the history of its predecessors.

    title: JWT Authentication with FastAPI and AWS Cognito
  - author: Ankush Thakur
    author_link: https://geekflare.com/author/ankush/
    link: https://geekflare.com/python-asynchronous-web-frameworks/
    title: Top 5 Asynchronous Web Frameworks for Python
  - author: Nico Axtmann
    author_link: https://www.linkedin.com/in/nico-axtmann

```Python hl_lines="1"
async def get_burgers(number: int):
    # Do some asynchronous stuff to create the burgers
    return burgers
```

...`def`를 사용하는 대신:

```Python hl_lines="2"
# This is not asynchronous
def get_sequential_burgers(number: int):
    # Do some sequential stuff to create the burgers
    return burgers
```