```

`status` is provided directly by Starlette.

It contains a group of named constants (variables) with integer status codes.

For example:

* 200: `status.HTTP_200_OK`
* 403: `status.HTTP_403_FORBIDDEN`
* etc.

It can be convenient to quickly access HTTP (and WebSocket) status codes in your app, using autocompletion for the name without having to remember the integer status codes by memory.

```Python
from myapp import app
```

#### More details

Let's say your file is named `myapp.py`.

If you run it with:

<div class="termy">

```console
$ python myapp.py
```

</div>

then the internal variable `__name__` in your file, created automatically by Python, will have as value the string `"__main__"`.

So, the section:

```Python

The <abbr title="specification">spec</abbr> requires the fields to be exactly named `username` and `password`, and to be sent as form fields, not JSON.

With `Form` you can declare the same configurations as with `Body` (and `Query`, `Path`, `Cookie`), including validation, examples, an alias (e.g. `user-name` instead of `username`), etc.

!!! info
    `Form` is a class that inherits directly from `Body`.

!!! tip

```Python hl_lines="48-52"
{!../../../docs_src/websockets/tutorial001.py!}
```

You can receive and send binary, text, and JSON data.

## Try it

If your file is named `main.py`, run your application with:

<div class="termy">

```console
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

```

!!! tip
    Peewee creates several magic attributes.

    It will automatically add an `id` attribute as an integer to be the primary key.

    It will chose the name of the tables based on the class names.

    For the `Item`, it will create an attribute `owner_id` with the integer ID of the `User`. But we don't declare it anywhere.

## Create the Pydantic models

        bool,
        Doc(
            """
            Exclude from the output any fields that start with the name `_sa`.

            This is mainly a hack for compatibility with SQLAlchemy objects, they
            store internal SQLAlchemy-specific state in attributes named with `_sa`,
            and those objects can't (and shouldn't be) serialized to JSON.
            """
        ),
    ] = True,

2. By using a `with` block, we make sure that the file-like object is closed after the generator function is done. So, after it finishes sending the response.
3. This `yield from` tells the function to iterate over that thing named `file_like`. And then, for each part iterated, yield that part as coming from this generator function.

    So, it is a generator function that transfers the "generating" work to something else internally.

And the spec says that the fields have to be named like that. So `user-name` or `email` wouldn't work.

But don't worry, you can show it as you wish to your final users in the frontend.

And your database models can use any other names you want.

[19515] [INFO] Application startup complete.
```

</div>

Let's see what each of those options mean:

* `main:app`: This is the same syntax used by Uvicorn, `main` means the Python module named "`main`", so, a file `main.py`. And `app` is the name of the variable that is the **FastAPI** application.
    * You can imagine that `main:app` is equivalent to a Python `import` statement like:

        ```Python
        from main import app

The process that happens when your API app calls the *external API* is named a "callback". Because the software that the external developer wrote sends a request to your API and then your API *calls back*, sending a request to an *external API* (that was probably created by the same developer).