An <a href="https://en.wikipedia.org/wiki/Environment_variable" class="external-link" target="_blank">environment variable</a> (also known as "env var") is a variable that lives outside of the Python code, in the operating system, and could be read by your Python code (or by other programs as well).

Estos **type hints** son una nueva sintaxis, desde Python 3.6+, que permite declarar el <abbr title="por ejemplo: str, int, float, bool">tipo</abbr> de una variable.

Usando las declaraciones de tipos para tus variables, los editores y otras herramientas pueden proveerte un soporte mejor.

### Classes en tant que types

Vous pouvez aussi déclarer une classe comme type d'une variable.

Disons que vous avez une classe `Person`, avec une variable `name` :

```Python hl_lines="1-3"
{!../../../docs_src/python_types/tutorial010.py!}
```

Vous pouvez ensuite déclarer une variable de type `Person` :

```Python hl_lines="6"
{!../../../docs_src/python_types/tutorial010.py!}
```

Doing that in separated functions that don't share logic or variables together is more difficult as you would need to store values in global variables or similar tricks.

Because of that, it's now recommended to instead use the `lifespan` as explained above.

## Technical Details

        "bar",
        "foo"
    ]
}
```

## Recap

Declare headers with `Header`, using the same common pattern as `Query`, `Path` and `Cookie`.

Mais vous pouvez toujours changer et mettre à jour toutes les configurations avec des variables d'environnement ou des fichiers de configuration.

!!! tip "Astuce"

# Status Codes

You can import the `status` module from `fastapi`:

```python
from fastapi import status
```

`status` is provided directly by Starlette.

It contains a group of named constants (variables) with integer status codes.

For example:

* 200: `status.HTTP_200_OK`
* 403: `status.HTTP_403_FORBIDDEN`
* etc.

# Path Parameters

You can declare path "parameters" or "variables" with the same syntax used by Python format strings:

```Python hl_lines="6-7"
{!../../../docs_src/path_params/tutorial001.py!}
```

The value of the path parameter `item_id` will be passed to your function as the argument `item_id`.

## Caveat

If you need to perform heavy background computation and you don't necessarily need it to be run by the same process (for example, you don't need to share memory, variables, etc), you might benefit from using other bigger tools like <a href="https://docs.celeryq.dev" class="external-link" target="_blank">Celery</a>.

that, with Peewee's current implementation, multiple tasks could be using the same `threading.local` variable and end up sharing the same connection and data (that they shouldn't), and at the same time, if they execute sync I/O-blocking code in a threadpool (as with normal `def` functions in FastAPI, in *path operations*  and dependencies), that code won't have access to the database state variables, even while it's part of the same request and it should be able to get access to the same database state....