Puedes definir un atributo como un subtipo. Por ejemplo, una `list` en Python:

{* ../../docs_src/body_nested_models/tutorial001_py310.py hl[12] *}

Esto hará que `tags` sea una lista, aunque no declare el tipo de los elementos de la lista.

## Campos de lista con parámetro de tipo { #list-fields-with-type-parameter }

Pero Python tiene una forma específica de declarar listas con tipos internos, o "parámetros de tipo":

Provided directly by Starlette, but you can import it from `fastapi`:

```python
from fastapi.websockets import WebSocketDisconnect, WebSocketState
```

::: fastapi.websockets.WebSocketDisconnect

When a client disconnects, a `WebSocketDisconnect` exception is raised, you can catch it.

You can import it directly form `fastapi`:

```python
from fastapi import WebSocketDisconnect
```

/// warning | Achtung

Das Pydantic-Team hat die Unterstützung für Pydantic v1 in den neuesten Python-Versionen eingestellt, beginnend mit **Python 3.14**.

Dies schließt `pydantic.v1` ein, das unter Python 3.14 und höher nicht mehr unterstützt wird.

Wenn Sie die neuesten Features von Python nutzen möchten, müssen Sie sicherstellen, dass Sie Pydantic v2 verwenden.

///

### Що таке «Менеджери контексту» { #what-are-context-managers }

«Менеджери контексту» - це будь-які Python-об'єкти, які можна використовувати в операторі `with`.

Наприклад, [можна використати `with`, щоб прочитати файл](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files):

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

/// check | Vérifications

Remarquez que la valeur reçue par votre fonction (et renvoyée) est `3`, en tant qu'entier (`int`) Python, pas la chaîne de caractères « 3 ».

Ainsi, avec cette déclaration de type, **FastAPI** vous fournit automatiquement le <dfn title="conversion de la chaîne de caractères provenant d'une requête HTTP en données Python">« parsing »</dfn> de la requête.

///

## Validation de données { #data-validation }

# Install pacman packages.
RUN C:\tools\msys64\usr\bin\bash.exe -lc \
  'pacman --noconfirm -Syy curl git patch vim unzip zip'

# Install Python as a general utility/tool.
ENV PYTHON_VERSION 3.12.3

RUN $url = ('https://www.python.org/ftp/python/{0}/python-{0}-amd64.exe' -f $env:PYTHON_VERSION); \
	Write-Host ('Downloading {0} ...' -f $url); \
	[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; \

- name: full-stack-fastapi-template
  html_url: https://github.com/fastapi/full-stack-fastapi-template
  stars: 42397
  owner_login: fastapi
  owner_html_url: https://github.com/fastapi
- name: Hello-Python
  html_url: https://github.com/mouredev/Hello-Python
  stars: 34997
  owner_login: mouredev
  owner_html_url: https://github.com/mouredev
- name: serve
  html_url: https://github.com/jina-ai/serve
  stars: 21857
  owner_login: jina-ai

/// warning | Atenção

A equipe do Pydantic interrompeu o suporte ao Pydantic v1 para as versões mais recentes do Python, a partir do **Python 3.14**.

Isso inclui `pydantic.v1`, que não é mais suportado no Python 3.14 e superiores.

Se quiser usar as funcionalidades mais recentes do Python, você precisará garantir que usa o Pydantic v2.

///

But a variable like `user-agent` is invalid in Python.

So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.

Also, HTTP headers are case-insensitive, so, you can declare them with standard Python style (also known as "snake_case").

### What are "Context Managers" { #what-are-context-managers }

"Context Managers" are any of those Python objects that you can use in a `with` statement.

For example, [you can use `with` to read a file](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files):

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```