The **Advanced User Guide**, builds on this, uses the same concepts, and teaches you some extra features.

But you should first read the **Tutorial - User Guide** (what you are reading right now).

## Do not Separate Schemas

Now, there are some cases where you might want to have the **same schema for input and output**.

Probably the main use case for this is if you already have some autogenerated client code/SDKs and you don't want to update all the autogenerated client code/SDKs yet, you probably will want to do it at some point, but maybe not right now.

```
.
├── app
│   ├── __init__.py
│   ├── main.py
└── static/
```

### Download the files

Download the static files needed for the docs and put them on that `static/` directory.

You can probably right-click each link and select an option similar to `Save link as...`.

**Swagger UI** uses the files:

The benefit of raising an exception over `return`ing a value will be more evident in the section about Dependencies and Security.

```Python hl_lines="5-6"
{!../../../docs_src/dependencies/tutorial007.py!}
```

!!! tip
    You can use `async` or regular functions.

    **FastAPI** will do the right thing with each, the same as with normal dependencies.

## A dependency with `yield` and `try`

If you use a `try` block in a dependency with `yield`, you'll receive any exception that was thrown when using the dependency.

You can also create an environment variable only for a specific program invocation, that is only available to that program, and only for its duration.

To do that, create it right before the program itself, on the same line:

<div class="termy">

```console
// Create an env var MY_NAME in line for this program call
$ MY_NAME="Wade Wilson" python main.py