第一个步骤是安装 FastAPI。

为了使用本教程，你可能需要安装所有的可选依赖及对应功能：

<div class="termy">

```console
$ pip install "fastapi[all]"

---> 100%
```

</div>

......以上安装还包括了 `uvicorn`，你可以将其用作运行代码的服务器。

/// note

你也可以分开来安装。

假如你想将应用程序部署到生产环境，你可能要执行以下操作：

```
pip install fastapi
```

并且安装`uvicorn`来作为服务器：

```
pip install "uvicorn[standard]"
```

然后对你想使用的每个可选依赖项也执行相同的操作。

///

  // if the object being admitted is modified by other admission plugins after the initial webhook call.
  // Webhooks that specify this option *must* be idempotent, able to process objects they previously admitted.
  // Note:
  // * the number of additional invocations is not guaranteed to be exactly one.
  // * if additional invocations result in further modifications to the object, webhooks are not guaranteed to be invoked again.

message MetricSpec {
  // type is the type of metric source.  It should be one of "ContainerResource", "External",
  // "Object", "Pods" or "Resource", each mapping to a matching field in the object.
  // Note: "ContainerResource" type is available on when the feature-gate
  // HPAContainerMetrics is enabled
  optional string type = 1;

  // object refers to a metric describing a single kubernetes object

{!../../docs_src/app_testing/tutorial001.py!}
```

/// tip

👀 👈 🔬 🔢 😐 `def`, 🚫 `async def`.

 & 🤙 👩‍💻 😐 🤙, 🚫 ⚙️ `await`.

👉 ✔ 👆 ⚙️ `pytest` 🔗 🍵 🤢.

///

/// note | "📡 ℹ"

👆 💪 ⚙️ `from starlette.testclient import TestClient`.

**FastAPI** 🚚 🎏 `starlette.testclient` `fastapi.testclient` 🏪 👆, 👩‍💻. ✋️ ⚫️ 👟 🔗 ⚪️➡️ 💃.

///

/// tip

 * equals}, {@code hashCode} and {@code compareTo} because instances are expected to be mutated, and
 * so are not useful as collection keys.
 *
 * <p>jsr166e note: This class is targeted to be placed in java.util.concurrent.atomic.
 *
 * @since 1.8
 * @author Doug Lea
 */
@ElementTypesAreNonnullByDefault

 * equals}, {@code hashCode} and {@code compareTo} because instances are expected to be mutated, and
 * so are not useful as collection keys.
 *
 * <p>jsr166e note: This class is targeted to be placed in java.util.concurrent.atomic.
 *
 * @since 1.8
 * @author Doug Lea
 */
@ElementTypesAreNonnullByDefault

/// tip

Prefer to use the `Annotated` version if possible.

///

```Python hl_lines="8  49  56-57  60-61  70-76"
{!> ../../docs_src/security/tutorial004.py!}
```

////

/// note | "笔记"

查看新的（伪）数据库 `fake_users_db`，就能看到哈希后的密码：`"$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW"`。

///

## 处理 JWT 令牌

导入已安装的模块。

创建用于 JWT 令牌签名的随机密钥。

使用以下命令，生成安全的随机密钥：

   * them under J2CL—or, as an unfortunate side effect, under GWT. We do still give the fields
   * themselves their proper values under GWT, since GWT's EnumMap does need the Class instance.
   *
   * Note that sometimes these fields *do* have correct values under J2CL: They will if the caller
   * calls `create(Foo.class)`, rather than `create(map)`. That's fine; we just shouldn't rely on
   * it.
   */

   * them under J2CL—or, as an unfortunate side effect, under GWT. We do still give the fields
   * themselves their proper values under GWT, since GWT's EnumMap does need the Class instance.
   *
   * Note that sometimes these fields *do* have correct values under J2CL: They will if the caller
   * calls `create(Foo.class)`, rather than `create(map)`. That's fine; we just shouldn't rely on
   * it.
   */

   * behavior as {@link #get}, returning a live collection. When passed a key that is not present,
   * however, {@code asMap().get(Object)} returns {@code null} instead of an empty collection.
   *
   * <p><b>Note:</b> The returned map's values are guaranteed to be of type {@link SortedSet}. To
   * obtain this map with the more specific generic type {@code Map<K, SortedSet<V>>}, call {@link