* Eine gemeinsame Logik haben (die gleiche Code-Logik immer und immer wieder).
* Datenbankverbindungen teilen.
* Sicherheit, Authentifizierung, Rollenanforderungen, usw. durchsetzen.
* Und viele andere Dinge ...

All dies, während Sie Codeverdoppelung minimieren.

## Erste Schritte { #first-steps }

Sehen wir uns ein sehr einfaches Beispiel an. Es ist so einfach, dass es vorerst nicht sehr nützlich ist.

x[:], x[:]) return x } for len(m) >= aes.BlockSize { subtle.XORBytes(x[:], m[:aes.BlockSize], x[:]) if len(m) == aes.BlockSize { // Final complete block. subtle.XORBytes(x[:], c.k1[:], x[:]) } aes.EncryptBlockInternal(&c.b, x[:], x[:]) m = m[aes.BlockSize:] } if len(m) > 0 { // Final incomplete block. subtle.XORBytes(x[:], m, x[:]) subtle.XORBytes(x[:], c.k2[:], x[:]) x[len(m)] ^= 0b10000000 aes.EncryptBlockInternal(&c.b, x[:], x[:]) } return x } // shiftLeft sets x to x << 1, and returns MSB₁(x)....

   *
   * @param lists the lists to choose elements from, in the order that the elements chosen from
   *     those lists should appear in the resulting lists
   * @param <B> any common base class shared by all axes (often just {@link Object})
   * @return the Cartesian product, as an immutable list containing immutable lists
   * @throws IllegalArgumentException if the size of the cartesian product would be greater than

Wie funktioniert das? Schauen wir uns das mal an. 🤓

### Typannotationen und Tooling { #type-annotations-and-tooling }

Sehen wir uns zunächst an, wie Editor, mypy und andere Tools dies sehen würden.

`BaseUser` verfügt über die Basis-Felder. Dann erbt `UserIn` von `BaseUser` und fügt das Feld `password` hinzu, sodass es nun alle Felder beider Modelle hat.

> **NOTE:** Do **NOT** run `gradle build` on the local development environment,
> even if you have Gradle or Develocity build caching enabled for the project.
> The Gradle Build Tool repository is massive, and it will take ages to build on
> a local machine without necessary parallelization and caching.
> The full test suites are executed on the CI instance for multiple configurations,

///

## The main `FastAPI` { #the-main-fastapi }

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI` { #import-fastapi }

 *
 * <p>Operations on this class make no guarantees about the ordering of elements with equal
 * priority. If you need to enforce an ordering, you can define custom classes or comparators that
 * use a secondary key to break ties in primary priority values. For example, here is a class that
 * applies first-in-first-out tie-breaking to comparable elements. To use it, you would insert a
 * {@code new FIFOEntry(anEntry)} instead of a plain entry object.
 *

      factory.setAccessible(true);
    }
    // Sorts methods/constructors with the least number of parameters first since it's likely easier
    // to fill dummy parameter values for them. Ties are broken by name then by the string form of
    // the parameter list.
    return BY_NUMBER_OF_PARAMETERS
        .compound(BY_METHOD_NAME)
        .compound(BY_PARAMETERS)
        .immutableSortedCopy(factories);

  }

  /**
   * Compares strings in natural order except that null comes immediately before a given value. This
   * works better than Ordering.natural().nullsFirst() because, if null comes before all other
   * values, it lies outside the submap/submultiset ranges we test, and the variety of tests that
   * exercise null handling fail on those subcollections.
   */

```

## `APIRouter` { #apirouter }

Supposons que le fichier dédié à la gestion des utilisateurs soit le sous-module `/app/routers/users.py`.

Vous voulez séparer les *chemins d'accès* liés à vos utilisateurs du reste du code pour le garder organisé.

Mais cela fait toujours partie de la même application/API web **FastAPI** (cela fait partie du même « package Python »).