**FastAPI**) основаны на <a href="https://anyio.readthedocs.io/en/stable/" class="external-link" target="_blank">AnyIO</a>, что делает их совместимыми как со стандартной библиотекой <a href="https://docs.python.org/3/library/asyncio-task.html" class="external-link" target="_blank">asyncio</a> в Python, так и с <a href="https://trio.readthedocs.io/en/stable/" class="external-link" target="_blank">Trio</a>.<!--http://new.gramota.ru/spravka/buro/search-answer?s=285295-->

В частности, вы можете...

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

<a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 的第二个参数是要返回的默认值。

如果没有提供默认值，默认为 `None`，此处我们提供了 `"World"` 作为要使用的默认值。

///

然后，您可以调用该 Python 程序：

<div class="termy">

```console
// 这里我们还没有设置环境变量
$ python main.py

* <a href="https://www.uvicorn.org/" class="external-link" target="_blank">Uvicorn</a>: a high performance ASGI server.
* <a href="https://hypercorn.readthedocs.io/" class="external-link" target="_blank">Hypercorn</a>: an ASGI server compatible with HTTP/2 and Trio among other features.
* <a href="https://github.com/django/daphne" class="external-link" target="_blank">Daphne</a>: the ASGI server built for Django Channels.

### Check it

Open your browser at <a href="http://127.0.0.1:8000" class="external-link" target="_blank">http://127.0.0.1:8000</a>.

You will see the JSON response as:

```JSON
{"message": "Hello World"}
```

### Interactive API docs

Now go to <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

👉 🤔 ⚫️ ⚠ 🚚 👫 🌐 🔢 👈 ✍ 🈸.

## 🌐 🔢

/// tip

🚥 👆 ⏪ 💭 ⚫️❔ "🌐 🔢" & ❔ ⚙️ 👫, 💭 🆓 🚶 ⏭ 📄 🔛.

///

<a href="https://en.wikipedia.org/wiki/Environment_variable" class="external-link" target="_blank">🌐 🔢</a> (💭 "🇨🇻 {") 🔢 👈 🖖 🏞 🐍 📟, 🏃‍♂ ⚙️, &amp; 💪 ✍ 👆 🐍 📟 (⚖️ 🎏 📋 👍).

👆 💪 ✍ &amp; ⚙️ 🌐 🔢 🐚, 🍵 💆‍♂ 🐍:

//// tab | 💾, 🇸🇻, 🚪 🎉

<div class="termy">

```console

Aqui veremos um exemplo usando <a href="https://sqlmodel.tiangolo.com/" class="external-link" target="_blank">SQLModel</a>.

**SQLModel** é construído sobre <a href="https://www.sqlalchemy.org/" class="external-link" target="_blank">SQLAlchemy</a> e Pydantic. Ele foi criado pelo mesmo autor do **FastAPI** para ser o par perfeito para aplicações **FastAPI** que precisam usar **bancos de dados SQL**.

For example:

* <a href="https://code.visualstudio.com/docs/python/environments#_select-and-activate-an-environment" class="external-link" target="_blank">VS Code</a>
* <a href="https://www.jetbrains.com/help/pycharm/creating-virtual-environment.html" class="external-link" target="_blank">PyCharm</a>

/// tip

You normally have to do this only **once**, when you create the virtual environment.

///

请记住可以 <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">用'X-' 前缀</a>添加专有自定义请求头.

但是如果你想让浏览器中的客户端看到你的自定义请求头, 你需要把它们加到 CORS 配置 ([CORS (Cross-Origin Resource Sharing)](cors.md){.internal-link target=_blank}) 的 `expose_headers` 参数中,在 <a href="https://www.starlette.io/middleware/#corsmiddleware" class="external-link" target="_blank">Starlette's CORS docs</a>文档中.

///

/// note | "技术细节"

所以 OpenAPI为了相似的目的定义了自己的 <a href="https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#fixed-fields-20" class="external-link" target="_blank">`example`</a> (使用 `example`, 而不是 `examples`), 这也是文档 UI 所使用的 (使用 Swagger UI).

Esse é o motivo das versões atuais estarem em `0.x.x`, significando que em cada versão pode haver mudanças significativas, tudo isso seguindo as <a href="https://semver.org/lang/pt-BR/" class="external-link" target="_blank">convenções de controle de versão semântica.</a>