Cette syntaxe `@something` en Python est appelée un "décorateur".

Vous la mettez au dessus d'une fonction. Comme un joli chapeau décoratif (j'imagine que ce terme vient de là 🤷🏻‍♂).

Un "décorateur" prend la fonction en dessous et en fait quelque chose.

Dans notre cas, ce décorateur dit à **FastAPI** que la fonction en dessous correspond au **chemin** `/` avec l'**opération** `get`.

///

## Motivations

Prenons un exemple simple :

{*../../docs_src/python_types/tutorial001.py*}

Exécuter ce programe affiche :

```
John Doe
```

La fonction :

* Prend un `first_name` et un `last_name`.
* Convertit la première lettre de chaque paramètre en majuscules grâce à `title()`.
* Concatène les résultats avec un espace entre les deux.

{*../../docs_src/python_types/tutorial001.py hl[2] *}

border-top-right-radius: 0;\n  border-bottom-right-radius: 0;\n}\n\n.input-group-prepend,\n.input-group-append {\n  display: -ms-flexbox;\n  display: flex;\n}\n\n.input-group-prepend .btn,\n.input-group-append .btn {\n  position: relative;\n  z-index: 2;\n}\n\n.input-group-prepend .btn:focus,\n.input-group-append .btn:focus {\n  z-index: 3;\n}\n\n.input-group-prepend .btn + .btn,\n.input-group-prepend .btn + .input-group-text,\n.input-group-prepend .input-group-text + .input-group-text,\n.input-group-prepend .input-group-text...

    /*
     * If greatestOf() promised to be implemented as reverse().leastOf(), this
     * test would be enough. It doesn't... but we'll cheat and act like it does
     * anyway. There's a comment there to remind us to fix this if we change it.
     */
    List<Integer> list = asList(3, 1, 3, 2, 4, 2, 4, 3);
    assertEquals(asList(4, 4, 3, 3), numberOrdering.greatestOf(list, 4));
  }

    /*
     * If greatestOf() promised to be implemented as reverse().leastOf(), this
     * test would be enough. It doesn't... but we'll cheat and act like it does
     * anyway. There's a comment there to remind us to fix this if we change it.
     */
    List<Integer> list = asList(3, 1, 3, 2, 4, 2, 4, 3);
    assertEquals(asList(4, 4, 3, 3), numberOrdering.greatestOf(list, 4));
  }

Pour expliquer la différence, voici une histoire de burgers :

#### Burgers concurrents

Vous amenez votre crush 😍 dans votre fast food 🍔 favori, et faites la queue pendant que le serveur 💁 prend les commandes des personnes devant vous.

<img src="/img/async/concurrent-burgers/concurrent-burgers-01.png" class="illustration">

### Tests { #tests }

* Help me check that the PR has **tests**.

* Check that the tests **fail** before the PR. 🚨

* Then check that the tests **pass** after the PR. ✅

* Many PRs don't have tests, you can **remind** them to add tests, or you can even **suggest** some tests yourself. That's one of the things that consume most time and you can help a lot with that.

* Then also comment what you tried, that way I'll know that you checked it. 🤓

        LockGraphNode preAcquiredLock = entry.getKey();
        found = preAcquiredLock.findPathTo(node, seen);
        if (found != null) {
          // One of this node's allowedPriorLocks found a path. Prepend an
          // ExampleStackTrace(preAcquiredLock, this) to the returned chain of
          // ExampleStackTraces.
          ExampleStackTrace path = new ExampleStackTrace(preAcquiredLock, this);

  private static final int CUTOFF = (int) (MAX_TABLE_SIZE * DESIRED_LOAD_FACTOR);

  /**
   * Returns an array size suitable for the backing array of a hash table that uses open addressing
   * with linear probing in its implementation. The returned size is the smallest power of two that
   * can hold setSize elements with the desired load factor. Always returns at least setSize + 2.
   */

        LockGraphNode preAcquiredLock = entry.getKey();
        found = preAcquiredLock.findPathTo(node, seen);
        if (found != null) {
          // One of this node's allowedPriorLocks found a path. Prepend an
          // ExampleStackTrace(preAcquiredLock, this) to the returned chain of
          // ExampleStackTraces.
          ExampleStackTrace path = new ExampleStackTrace(preAcquiredLock, this);