## Generate a TypeScript Frontend Client

Let's start with a simple FastAPI application:

=== "Python 3.9+"

    ```Python hl_lines="7-9  12-13  16-17  21"
    {!> ../../../docs_src/generate_clients/tutorial001_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9-11  14-15  18  19  23"
    {!> ../../../docs_src/generate_clients/tutorial001.py!}
    ```

Importez `List` (avec un `L` majuscule) depuis `typing`.

```Python hl_lines="1"
{!../../../docs_src/python_types/tutorial006.py!}
```

Déclarez la variable, en utilisant la syntaxe des deux-points (`:`).

Et comme type, mettez `List`.

Les listes étant un type contenant des types internes, mettez ces derniers entre crochets (`[`, `]`) :

```Python hl_lines="4"
{!../../../docs_src/python_types/tutorial006.py!}
```

For example:

```Python hl_lines="4-7"
{!../../../docs_src/behind_a_proxy/tutorial003.py!}
```

Will generate an OpenAPI schema like:

```JSON hl_lines="5-7"
{
    "openapi": "3.1.0",
    // More stuff here
    "servers": [
        {
            "url": "/api/v1"
        },
        {

=== "Python 3.10+"

    ```Python hl_lines="1  4-6  9-10  21-22  25-26"
    {!> ../../../docs_src/sql_databases/sql_app_py310/schemas.py!}
    ```

=== "Python 3.9+"

    ```Python hl_lines="3  6-8  11-12  23-24  27-28"
    {!> ../../../docs_src/sql_databases/sql_app_py39/schemas.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="3  6-8  11-12  23-24  27-28"

## 더 큰 동기부여

아래 함수를 보면, 이미 타입 힌트가 적용되어 있는 걸 볼 수 있습니다:

```Python hl_lines="1"
{!../../../docs_src/python_types/tutorial003.py!}
```

편집기가 변수의 타입을 알고 있기 때문에, 자동완성 뿐 아니라 에러도 확인할 수 있습니다:

<img src="/img/python-types/image04.png">

이제 고쳐야하는 걸 알기 때문에, `age`를 `str(age)`과 같이 문자열로 바꾸게 됩니다:

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial004.py!}
```

## 타입 선언

    ```Python hl_lines="17  19-21"
    {!> ../../../docs_src/settings/app02_an_py39/main.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="17  19-21"
    {!> ../../../docs_src/settings/app02_an/main.py!}
    ```

=== "Python 3.8+ 非注解版本"

    !!! tip
        如果可能，请尽量使用 `Annotated` 版本。

    ```Python hl_lines="16  18-20"
    {!> ../../../docs_src/settings/app02/main.py!}
    ```

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

!!! note
    Si vous ne connaissez pas la différence, allez voir la section [Concurrence : *"Vous êtes pressés ?"*](../async.md#vous-etes-presses){.internal-link target=_blank}.

### Étape 5 : retourner le contenu

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

アプリ開発中に本体のログを取ってデバッグしたり、ユーザーに返したりなどに使用することができます。

```Python hl_lines="14"
{!../../../docs_src/handling_errors/tutorial005.py!}
```

ここで、以下のような無効な項目を送信してみてください:

```JSON
{
  "title": "towel",
  "size": "XL"
}
```

受信したボディを含むデータが無効であることを示すレスポンスが表示されます:

```JSON hl_lines="12 13 14 15"
{
  "detail": [
    {
      "loc": [
        "body",

=== "🐍 3️⃣.6️⃣ & 🔛"

    ```Python hl_lines="3  6-8  11-12  23-24  27-28"
    {!> ../../../docs_src/sql_databases/sql_app/schemas.py!}
    ```

=== "🐍 3️⃣.9️⃣ & 🔛"

    ```Python hl_lines="3  6-8  11-12  23-24  27-28"
    {!> ../../../docs_src/sql_databases/sql_app_py39/schemas.py!}
    ```

=== "🐍 3️⃣.1️⃣0️⃣ & 🔛"

    ```Python hl_lines="1  4-6  9-10  21-22  25-26"

```Python hl_lines="1  3" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

### *Path operations* with `APIRouter`

And then you use it to declare your *path operations*.

Use it the same way you would use the `FastAPI` class:

```Python hl_lines="6  11  16" title="app/routers/users.py"