```Python hl_lines="7"
{!../../../docs_src/first_steps/tutorial003.py!}
```

!!! note "Nota"
    Se você não sabe a diferença, verifique o [Async: *"Com pressa?"*](../async.md#com-pressa){.internal-link target=_blank}.

### Passo 5: retorne o conteúdo

```Python hl_lines="8"
{!../../../docs_src/first_steps/tutorial001.py!}
```

# Security - First Steps

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

Joshua Hanson <******@****.***> 1710356539 -0600

Nils Lindemann <******@****.***> 1713469999 +0200

Joshua Hanson <******@****.***> 1710356539 -0600

```Python hl_lines="1"
{!../../../docs_src/first_steps/tutorial001.py!}
```

`FastAPI` 🐍 🎓 👈 🚚 🌐 🛠️ 👆 🛠️.

!!! note "📡 ℹ"
    `FastAPI` 🎓 👈 😖 🔗 ⚪️➡️ `Starlette`.

    👆 💪 ⚙️ 🌐 <a href="https://www.starlette.io/" class="external-link" target="_blank">💃</a> 🛠️ ⏮️ `FastAPI` 💁‍♂️.

### 🔁 2️⃣: ✍ `FastAPI` "👐"

```Python hl_lines="3"
{!../../../docs_src/first_steps/tutorial001.py!}
```

  @Override
  public UnmodifiableIterator<C> descendingIterator() {
    return new AbstractSequentialIterator<C>(last()) {
      final C first = first();

      @Override
      @CheckForNull
      protected C computeNext(C previous) {
        return equalsOrThrow(previous, first) ? null : domain.previous(previous);
      }
    };
  }

    @Override
    public int compare(@Nullable String first, @Nullable String second) {
      if (first == second) {
        return 0;
      } else if (first == null) {
        return -1;
      } else if (second == null) {
        return 1;
      } else if (first.length() != second.length()) {
        return first.length() - second.length();
      } else {
        return first.compareTo(second);
      }
    }
  }

        return new Pair<>(first, second);
    }

    /**
     * インスタンスを構築します。
     */
    public Pair() {
    }

    /**
     * インスタンスを構築します。
     *
     * @param first
     *            1番目の値
     * @param second
     *            2番目の値
     */
    public Pair(final T1 first, final T2 second) {
        this.first = first;
        this.second = second;

     1. Build a Gradle distribution with a fixed timestamp and hash it, but never use this distribution.
     2. Build a Gradle distribution with this hash as a version + fixed timestamp -> dogfood-first
     3. Build a Gradle distribution using dogfood-first with this hash as a version + fixed timestamp different from the one above -> dogfood-second
     4. Use dogfood-second to run a Gradle build which runs tests.

     */