"tax": 3.2
}
```

## Recap

You can add multiple body parameters to your *path operation function*, even though a request can only have a single body.

But **FastAPI** will handle it, give you the correct data in your function, and validate and document the correct schema in the *path operation*.

You can also declare singular values to be received as part of the body.

* Fix serialization when using `by_alias` or `exclude_unset` and returning data with Pydantic models. PR [#1074](https://github.com/tiangolo/fastapi/pull/1074) by [@juhovh-aiven](https://github.com/juhovh-aiven).
* Add Gitter chat to docs. PR [#1061](https://github.com/tiangolo/fastapi/pull/1061) by [@aakashnand](https://github.com/aakashnand).

* the data from the client to be sent through the network
* the data sent by your program to be received by the client through the network
* the contents of a file in the disk to be read by the system and given to your program
* the contents your program gave to the system to be written to disk
* a remote API operation
* a database operation to finish
* a database query to return the results
* etc.

And then, in each *path operation function* that needs to access the database we add it as a dependency.

But we are not using the value given by this dependency (it actually doesn't give any value, as it has an empty `yield`). So, we don't add it to the *path operation function* but to the *path operation decorator* in the `dependencies` parameter:

```Python hl_lines="32  40  47  59  65  72"

    ```Python hl_lines="13-14"
    {!> ../../../docs_src/dependencies/tutorial008c.py!}
    ```

In this case, the client will see an *HTTP 500 Internal Server Error* response as it should, given that we are not raising an `HTTPException` or similar, but the server will **not have any logs** or any other indication of what was the error. 😱

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

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# Features

## FastAPI features

**FastAPI** gives you the following:

### Based on open standards

### 💯

* 1️⃣0️⃣0️⃣ 💯 <abbr title="The amount of code that is automatically tested">💯 💰</abbr>.
* 1️⃣0️⃣0️⃣ 💯 <abbr title="Python type annotations, with this your editor and external tools can give you better support">🆎 ✍</abbr> 📟 🧢.
* ⚙️ 🏭 🈸.

## 💃 ⚒

    {!> ../../../docs_src/dependencies/tutorial001.py!}
    ```

Although you use `Depends` in the parameters of your function the same way you use `Body`, `Query`, etc, `Depends` works a bit differently.

You only give `Depends` a single parameter.

This parameter must be something like a function.

You **don't call it** directly (don't add the parenthesis at the end), you just pass it as a parameter to `Depends()`.

### Suggest solutions

* After being able to understand the question, you can give them a possible **answer**.

* In many cases, it's better to understand their **underlying problem or use case**, because there might be a better way to solve it than what they are trying to do.

### Ask to close

!!! note
    FastAPI will know that the value of `q` is not required because of the default value `= None`.

    The `Union` in `Union[str, None]` will allow your editor to give you better support and detect errors.

## Additional validation

We are going to enforce that even though `q` is optional, whenever it is provided, **its length doesn't exceed 50 characters**.