But you can have thousands of endpoints (*path operations*) using the same security system.

And all of them (or any portion of them that you want) can take the advantage of re-using these dependencies or any other dependencies you create.

And all these thousands of *path operations* can be as small as 3 lines:

=== "Python 3.10+"

    ```Python hl_lines="30-32"

* Put the contents of the document in a `UserInDB` model.

By creating a function that is only dedicated to getting your user from a `username` (or any other parameter) independent of your *path operation function*, you can more easily re-use it in multiple parts and also add <abbr title="Automated test, written in code, that checks if another piece of code is working correctly.">unit tests</abbr> for it:

```Python hl_lines="36-42"

Being able to use asynchronous functions in your tests could be useful, for example, when you're querying your database asynchronously. Imagine you want to test sending requests to your FastAPI application and then verify that your backend successfully wrote the correct data in the database, while using an async database library.

---

"_If you're looking to learn one **modern framework** for building REST APIs, check out **FastAPI** [...] It's fast, easy to use and easy to learn [...]_"

"_We've switched over to **FastAPI** for our **APIs** [...] I think you'll like it [...]_"

---

"_If you're looking to learn one **modern framework** for building REST APIs, check out **FastAPI** [...] It's fast, easy to use and easy to learn [...]_"

"_We've switched over to **FastAPI** for our **APIs** [...] I think you'll like it [...]_"

```Python
from starlette.exceptions import HTTPException as StarletteHTTPException
```

### Re-use os manipulares de exceção do **FastAPI**

Se você quer usar a exceção em conjunto com o mesmo manipulador de exceção *default* do **FastAPI**, você pode importar e re-usar esses manipuladores de exceção do `fastapi.exception_handlers`:

```Python hl_lines="2-5  15  21"

    ```Python hl_lines="8  13"
    {!> ../../../docs_src/dependencies/tutorial006.py!}
    ```

### Return values

And they can return values or not, the values won't be used.

So, you can re-use a normal dependency (that returns a value) you already use somewhere else, and even though the value won't be used, the dependency will be executed:

=== "Python 3.9+"

    ```Python hl_lines="11  16"

    This is because we want to include their *path operations* in the OpenAPI schema and the user interfaces.

    As we cannot just isolate them and "mount" them independently of the rest, the *path operations* are "cloned" (re-created), not included directly.

## Check the automatic API docs

Now, run `uvicorn`, using the module `app.main` and the variable `app`:

<div class="termy">

```console

* 🔧 Fix Ruff configuration unintentionally enabling and re-disabling mccabe complexity check. PR [#10893](https://github.com/tiangolo/fastapi/pull/10893) by [@jiridanek](https://github.com/jiridanek).

---

"_If you're looking to learn one **modern framework** for building REST APIs, check out **FastAPI** [...] It's fast, easy to use and easy to learn [...]_"

"_We've switched over to **FastAPI** for our **APIs** [...] I think you'll like it [...]_"