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

///

Then you could call that Python program:

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

The modules under this directory will be released exactly once each. Once that

**FastAPI** se encargará de leer esos datos del lugar correcto en lugar de JSON.

/// note | Detalles técnicos

Los datos de formularios normalmente se codifican usando el "media type" `application/x-www-form-urlencoded`.

Pero cuando el formulario incluye archivos, se codifica como `multipart/form-data`. Leerás sobre la gestión de archivos en el próximo capítulo.

    /*
     * Since we use AtomicReferenceFieldUpdaterAtomicHelper by default, we'll "obviously" use it
     * even when Unsafe isn't available. But it's nice to have a check here to make sure that
     * nothing somehow goes wrong as the JDK restricts access to Unsafe.
     */
    checkHelperVersion(NO_UNSAFE, "AtomicReferenceFieldUpdaterAtomicHelper");
    /*

    // contract to guarantee ordering among runnables we'd have to modify the logic here to allow
    // it.
    executeListener(runnable, executor);
  }

  /**
   * Runs this execution list, executing all existing pairs in the order they were added. However,
   * note that listeners added after this point may be executed before those previously added, and

		case isSysErrPathNotFound(err):
			// This is a special case should be handled only for
			// windows, because windows API does not return "not a
			// directory" error message. Handle this specifically
			// here.
			return errFileAccessDenied
		}
	}
	return err
}

// Reliably retries os.RemoveAll if for some reason os.RemoveAll returns
// syscall.ENOTEMPTY (children has files).

```

Assurez-vous d'utiliser toujours la forme **exec** pour garantir que FastAPI peut s'arrêter proprement et que les [événements de cycle de vie](../advanced/events.md) sont déclenchés.

Vous pouvez en lire davantage dans la [documentation Docker sur les formes shell et exec](https://docs.docker.com/reference/dockerfile/#shell-and-exec-form).

import jetbrains.buildServer.configs.kotlin.BuildSteps
import jetbrains.buildServer.configs.kotlin.DslContext
import jetbrains.buildServer.configs.kotlin.buildSteps.GradleBuildStep

fun DslContext.initForTest() {
    // Set the project id here, so we can use methods on the DslContext
    parentProjectId = AbsoluteId("Gradle")
    projectId = AbsoluteId("Gradle_Master")
    settingsRootId = AbsoluteId("GradleMaster")
    settingsRoot.name = "GradleMaster"

/// tip | Astuce

Les sections suivantes ne sont **pas nécessairement « avancées »**.

Et il est possible que, pour votre cas d'utilisation, la solution se trouve dans l'une d'entre elles.

///

## Lire d'abord le tutoriel { #read-the-tutorial-first }

Vous pouvez utiliser la plupart des fonctionnalités de **FastAPI** grâce aux connaissances du [Tutoriel - Guide de l'utilisateur](../tutorial/index.md).

    static String getMessageByCode(final int errcode) {
        /* Note there's a signedness error here because 0xC0000000 based values are
         * negative so it with NT_STATUS_SUCCESS (0) the binary search will not be
         * performed properly. The effect is that the code at index 1 is never found
         * (NT_STATUS_UNSUCCESSFUL). So here we factor out NT_STATUS_SUCCESS
         * as a special case (which it is).
         */