!!! tip
    Notice that in this case we are using a standard Python `open()` function that interacts with a file.

    So, it involves I/O (input/output), that requires "waiting" for things to be written to disk.

    But `open()` doesn't use `async` and `await`.

    So, we declare the event handler function with standard `def` instead of `async def`.

### `startup` and `shutdown` together

## External Courses

Although the [Tutorial - User Guide](../tutorial/index.md){.internal-link target=_blank} and this **Advanced User Guide** are written as a guided tutorial (like a book) and should be enough for you to **learn FastAPI**, you might want to complement it with additional courses.

    {!> ../../../docs_src/background_tasks/tutorial002.py!}
    ```

In this example, the messages will be written to the `log.txt` file *after* the response is sent.

If there was a query in the request, it will be written to the log in a background task.

And then another background task generated at the *path operation function* will write a message using the `email` path parameter.

## Technical Details

And it normally is a complex and "difficult" topic.

In many frameworks and systems just handling security and authentication takes a big amount of effort and code (in many cases it can be 50% or more of all the code written).

**FastAPI** provides several tools to help you deal with **Security** easily, rapidly, in a standard way, without having to study and learn all the security specifications.

But first, let's check some small concepts.

    By creating functions that are only dedicated to interacting with the database (get a user or an item) independent of your *path operation function*, you can more easily reuse them in multiple parts and also add <abbr title="Automated tests, written in code, that check if another piece of code is working correctly.">unit tests</abbr> for them.

### Create data

Now create utility functions to create data.

The steps are:

# Define this here and not in the main mkdocs.yml file because that one is auto
# updated and written, and the script would remove the env var
INHERIT: !ENV [INSIDERS_FILE, '../en/mkdocs.no-insiders.yml']
markdown_extensions:
  pymdownx.highlight:

    * So, by using FastAPI you are saving development time, bugs, lines of code, and you would probably get the same performance (or better) you would if you didn't use it (as you would have to implement it all in your code)....

    `OAuth2PasswordBearer` makes **FastAPI** know that it is a security scheme. So it is added that way to OpenAPI.

    But `OAuth2PasswordRequestForm` is just a class dependency that you could have written yourself, or you could have declared `Form` parameters directly.

    But as it's a common use case, it is provided by **FastAPI** directly, just to make it easier.

### Use the form data

!!! tip

But here's the key point.

The security and dependency injection stuff is written once.

And you can make it as complex as you want. And still, have it written only once, in a single place. With all the flexibility.

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

Es handelt sich um eine recht umfangreiche Spezifikation, und sie deckt mehrere komplexe Anwendungsfälle ab.

Sie umfasst Möglichkeiten zur Authentifizierung mithilfe eines „Dritten“ („third party“).

Das ist es, was alle diese „Login mit Facebook, Google, Twitter, GitHub“-Systeme unter der Haube verwenden.

### OAuth 1