在介绍依赖项与安全的章节中，您可以了解更多用 `raise` 异常代替 `return` 值的优势。

本例中，客户端用 `ID` 请求的 `item` 不存在时，触发状态码为 `404` 的异常：

{* ../../docs_src/handling_errors/tutorial001.py hl[11] *}

### 响应结果

请求为 `http://example.com/items/foo`（`item_id` 为 `「foo」`）时，客户端会接收到 HTTP 状态码 - 200 及如下 JSON 响应结果：

```JSON
{
  "item": "The Foo Wrestlers"
}

```

但如果客户端请求 `http://example.com/items/bar`（`item_id` `「bar」` 不存在时），则会接收到 HTTP 状态码 - 404（「未找到」错误）及如下 JSON 响应结果：

def test_get_item():
    response = client.get("/items/foo")
    assert response.status_code == 200, response.text
    assert response.json() == {"item": "The Foo Wrestlers"}


def test_get_item_not_found():
    response = client.get("/items/bar")
    assert response.status_code == 404, response.text
    assert response.headers.get("x-error") is None
    assert response.json() == {"detail": "Item not found"}


def test_openapi_schema():

from fastapi import FastAPI
from fastapi.responses import UJSONResponse

app = FastAPI()


@app.get("/items/", response_class=UJSONResponse)
async def read_items():

    }

    @Test
    public void test_update() throws Exception {
        SuggestItem[] items = getItemSet1();
        suggester.indexer().index(items);
        suggester.refresh();

        SuggestItem[] items2 = getItemSet1();
        SuggestIndexResponse response = suggester.indexer().index(items2);

        assertFalse(response.hasError());

        suggester.refresh();

class LargeOut(BaseModel):
    items: list[dict[str, Any]]
    metadata: dict[str, Any]


app = FastAPI()


@app.post("/sync/validated", response_model=ItemOut)
def sync_validated(item: ItemIn, dep: Annotated[int, Depends(dep_b)]):
    return ItemOut(name=item.name, value=item.value, dep=dep)


@app.get("/sync/dict-no-response-model")
def sync_dict_no_response_model():
    return {"name": "foo", "value": 123}

本例中，访问：

```
http://127.0.0.1:8000/items/foo?short=1
```

或

```
http://127.0.0.1:8000/items/foo?short=True
```

或

```
http://127.0.0.1:8000/items/foo?short=true
```

或

```
http://127.0.0.1:8000/items/foo?short=on
```

或

```
http://127.0.0.1:8000/items/foo?short=yes
```

{
  "item": "The Foo Wrestlers"
}
```

Mas se o cliente faz uma requisição para `http://example.com/items/bar` (ou seja, um não existente `item_id "bar"`), esse cliente receberá um HTTP status code 404 (o erro "não encontrado" — *not found error*), e uma resposta JSON:

```JSON
{
  "detail": "Item not found"
}
```

/// tip | Dica

```JSON
{
  "item": "The Foo Wrestlers"
}
```

Pero si el cliente solicita `http://example.com/items/bar` (un `item_id` inexistente `"bar"`), ese cliente recibirá un código de estado HTTP de 404 (el error "no encontrado"), y un response JSON de:

```JSON
{
  "detail": "Item not found"
}
```

/// tip | Consejo

http://127.0.0.1:8000/items/foo?short=True
```

або

```
http://127.0.0.1:8000/items/foo?short=true
```

або

```
http://127.0.0.1:8000/items/foo?short=on
```

або

```
http://127.0.0.1:8000/items/foo?short=yes
```

або будь-який інший варіант написання (великі літери, перша літера велика тощо), ваша функція побачить параметр `short` зі значенням `True` з типом даних `bool`. В іншому випадку – `False`.

        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/items/{item_id}": {
                "get": {
                    "responses": {
                        "404": {
                            "description": "The item was not found",
                            "content": {
                                "application/json": {