```Python hl_lines="3"
import os

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

/// tip

The second argument to <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> is the default value to return.

If not provided, it's `None` by default, here we provide `"World"` as the default value to use.

```Python hl_lines="3"
import os

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

/// tip

Het tweede argument van <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> is de standaardwaarde die wordt geretourneerd.

# WebSockets

Puedes usar <a href="https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API" class="external-link" target="_blank">WebSockets</a> con **FastAPI**.

## Instalar `WebSockets`

Asegúrate de crear un [entorno virtual](../virtual-environments.md){.internal-link target=_blank}, activarlo e instalar `websockets`:

<div class="termy">

```console
$ pip install websockets

---> 100%
```

</div>

          required: true
        - label: I already searched in Google "How to X in FastAPI" and didn't find any information.
          required: true
        - label: I already read and followed all the tutorial in the docs and didn't find an answer.
          required: true
        - label: I already checked if it is not related to FastAPI but to [Pydantic](https://github.com/pydantic/pydantic).
          required: true

# WebSockets

Sie können <a href="https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API" class="external-link" target="_blank">WebSockets</a> mit **FastAPI** verwenden.

## `WebSockets` installieren

Zuerst müssen Sie `WebSockets` installieren:

<div class="termy">

```console
$ pip install websockets

---> 100%
```

</div>

## WebSockets-Client

### In Produktion

次のようなJSONレスポンスが表示されます:

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

### 対話的APIドキュメント

次に、<a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>にアクセスします。

自動生成された対話的APIドキュメントが表示されます (<a href="https://github.com/swagger-api/swagger-ui" class="external-link" target="_blank">Swagger UI</a>で提供):

Це можна досягти за допомогою <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-after-validator" class="external-link" target="_blank">Pydantic's `AfterValidator`</a> в середині `Annotated`.

/// tip | Підказка

FastAPI використовує `.dict()` моделі Pydantic з <a href="https://docs.pydantic.dev/1.10/usage/exporting_models/#modeldict" class="external-link" target="_blank">параметром `exclude_unset`</a>, щоб досягти цього.

///

/// info | Інформація

Ви також можете використовувати:

* `response_model_exclude_defaults=True`
* `response_model_exclude_none=True`

///

/// info | Информация

Вы также можете использовать:

* `response_model_exclude_defaults=True`
* `response_model_exclude_none=True`

**📨** 💪 📊 📨 👩‍💻 👆 🛠️. **📨** 💪 💽 👆 🛠️ 📨 👩‍💻.

👆 🛠️ 🌖 🕧 ✔️ 📨 **📨** 💪. ✋️ 👩‍💻 🚫 🎯 💪 📨 **📨** 💪 🌐 🕰.

📣 **📨** 💪, 👆 ⚙️ <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">Pydantic</a> 🏷 ⏮️ 🌐 👫 🏋️ &amp; 💰.

/// info

📨 💽, 👆 🔜 ⚙️ 1️⃣: `POST` (🌅 ⚠), `PUT`, `DELETE` ⚖️ `PATCH`.