Os status codes na faixa dos 400 significam que houve um erro por parte do cliente.

Você se lembra de todos aqueles erros (e piadas) a respeito do "**404 Not Found**"?

## Use o `HTTPException`

Para retornar ao cliente *responses* HTTP com erros, use o `HTTPException`.

### Import `HTTPException`

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

```
1 validation error
path -> item_id
  value is not a valid integer (type=type_error.integer)
```

#### `RequestValidationError` vs. `ValidationError`

!!! warning "Achtung"
    Das folgende sind technische Details, die Sie überspringen können, wenn sie für Sie nicht wichtig sind.

                {
                    "loc": ["path", "item_id"],
                    "msg": "value is not a valid integer",
                    "type": "type_error.integer",
                }
            ]
        }
    )


def test_get_http_error():
    response = client.get("/items/3")
    assert response.status_code == 418, response.text
    assert response.json() == {"detail": "Nope! I don't like 3."}

        client.get("/model/modelX")
    assert err.value.errors() == [
        IsDict(
            {
                "type": "value_error",
                "loc": ("response", "name"),
                "msg": "Value error, name must end in A",
                "input": "modelX",
                "ctx": {"error": HasRepr("ValueError('name must end in A')")},
            }
        )
        | IsDict(

                    "loc": ["body", "file"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "fileb"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "token"],

                    "loc": ["body", "item"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "user"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "importance"],

                    "loc": ["query", "needy"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["query", "skip"],
                    "msg": "value is not a valid integer",
                    "type": "type_error.integer",
                },
                {
                    "loc": ["query", "limit"],

                    "loc": ["body", "grant_type"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "username"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "password"],

        {
            "detail": [
                {
                    "loc": ["body", "files"],
                    "msg": "field required",
                    "type": "value_error.missing",
                }
            ]
        }
    )


def test_post_body_json():
    response = client.post("/files/", json={"file": "Foo"})
    assert response.status_code == 422, response.text

```
1 validation error
path -> item_id
  value is not a valid integer (type=type_error.integer)
```

#### `RequestValidationError` или `ValidationError`

!!! warning "Внимание"
    Это технические детали, которые можно пропустить, если они не важны для вас сейчас.