```Python hl_lines="19-24  28"
{!../../../docs_src/additional_responses/tutorial002.py!}
```

!!! note
    Notice that you have to return the image using a `FileResponse` directly.

!!! info
    Unless you specify a different media type explicitly in your `responses` parameter, FastAPI will assume the response has the same media type as the main response class (default `application/json`).

### Always `raise` in Dependencies with `yield` and `except`

If you catch an exception in a dependency with `yield`, unless you are raising another `HTTPException` or similar, you should re-raise the original exception.

You can re-raise the same exception using `raise`:

=== "Python 3.9+"

    ```Python hl_lines="17"

#### Technical Details about ORM mode

SQLAlchemy and many others are by default "lazy loading".

That means, for example, that they don't fetch the data for relationships from the database unless you try to access the attribute that would contain that data.

For example, accessing the attribute `items`:

```Python
current_user.items
```

    ```

## Number validations: floats, greater than and less than

Number validations also work for `float` values.

Here's where it becomes important to be able to declare <abbr title="greater than"><code>gt</code></abbr> and not just <abbr title="greater than or equal"><code>ge</code></abbr>. As with it you can require, for example, that a value must be greater than `0`, even if it is less than `1`.

* **Intuitive**: Great editor support. <abbr title="also known as auto-complete, autocompletion, IntelliSense">Completion</abbr> everywhere. Less time debugging.
* **Easy**: Designed to be easy to use and learn. Less time reading docs.
* **Short**: Minimize code duplication. Multiple features from each parameter declaration. Fewer bugs.

        security_scopes=security_scopes,
    )


def get_parameterless_sub_dependant(*, depends: params.Depends, path: str) -> Dependant:
    assert callable(
        depends.dependency
    ), "A parameter-less dependency must have a callable dependency"
    return get_sub_dependant(depends=depends, dependency=depends.dependency, path=path)


def get_sub_dependant(
    *,
    depends: params.Depends,

used to defining trivial compute-only *path operation functions* with plain `def` for a tiny performance gain (about 100 nanoseconds), please note that in **FastAPI** the effect would be quite opposite. In these cases, it's better to use `async def` unless your *path operation functions* use code that performs blocking <abbr title="Input/Output: disk reading or writing, network communications.">I/O</abbr>.

Still, in both situations, chances are that **FastAPI** will [still be faster](ind...

Then, for the request in the next tab, your app will wait for one second less, and so on.

This means that it will end up finishing some of the last tabs' requests earlier than some of the previous ones.

        That's a lot of work they are doing, but if more FastAPI users came to help others like them just a little bit more, it would be much less effort for them (and you and me 😅).

        By asking questions in a structured way (following this) it will be much easier to help you.

数值校验同样适用于 `float` 值。

能够声明 <abbr title="大于"><code>gt</code></abbr> 而不仅仅是 <abbr title="大于等于"><code>ge</code></abbr> 在这个前提下变得重要起来。例如，你可以要求一个值必须大于 `0`，即使它小于 `1`。

因此，`0.5` 将是有效值。但是 `0.0`或 `0` 不是。

对于 <abbr title="less than"><code>lt</code></abbr> 也是一样的。

```Python hl_lines="11"
{!../../../docs_src/path_params_numeric_validations/tutorial006.py!}
```

## 总结