Here's a little bit of that history.

## Alternatives

I have been creating APIs with complex requirements for several years (Machine Learning, distributed systems, asynchronous jobs, NoSQL databases, etc), leading several teams of developers.

As part of that, I needed to investigate, test and use many alternatives.

The history of **FastAPI** is in great part the history of its predecessors.

Keep in mind that this means that the whole contents will be stored in memory. This will work well for small files.

But there are several cases in which you might benefit from using `UploadFile`.

## File Parameters with `UploadFile`

Define a file parameter with a type of `UploadFile`:

=== "Python 3.9+"

    ```Python hl_lines="14"

    ```

=== "Python 3.8+"

    ```Python hl_lines="81-83"
    {!> ../../../docs_src/websockets/tutorial003.py!}
    ```

To try it out:

* Open the app with several browser tabs.
* Write messages from them.
* Then close one of the tabs.

That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:

```

    If you don't know, you will learn what a "password hash" is in the [security chapters](security/simple-oauth2.md#password-hashing){.internal-link target=_blank}.

## Multiple models

Here's a general idea of how the models could look like with their password fields and the places where they are used:

=== "Python 3.10+"

    ```Python hl_lines="7  9  14  20  22  27-28  31-33  38-39"

    - deployment/manually.md
    - deployment/concepts.md
    - deployment/cloud.md
    - deployment/server-workers.md
    - deployment/docker.md
  - How To - Recipes:
    - how-to/index.md
    - how-to/general.md
    - how-to/graphql.md
    - how-to/custom-request-and-route.md
    - how-to/conditional-openapi.md
    - how-to/extending-openapi.md
    - how-to/separate-openapi-schemas.md

```Python hl_lines="17"
{!../../../docs_src/path_params/tutorial005.py!}
```

#### Obtén el *enumeration value*

Puedes obtener el valor exacto (un `str` en este caso) usando `model_name.value`, o en general, `your_enum_member.value`:

```Python hl_lines="20"
{!../../../docs_src/path_params/tutorial005.py!}
```

!!! tip "Consejo"
    También podrías obtener el valor `"lenet"` con `ModelName.lenet.value`.

The **default** value of the **function parameter** is the **actual default** value, that's more intuitive with Python in general. 😌

# Custom Response Classes - File, HTML, Redirect, Streaming, etc.

There are several custom response classes you can use to create an instance and return them directly from your *path operations*.

Read more about it in the [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).

You can import them directly from `fastapi.responses`:

```python
from fastapi.responses import (
    FileResponse,

    Feel free to skip this.

    Peewee is not recommended with FastAPI as it doesn't play well with anything async Python. There are several better alternatives.

!!! info
    These docs assume Pydantic v1.

### Parallel Burgers

Now let's imagine these aren't "Concurrent Burgers", but "Parallel Burgers".

You go with your crush to get parallel fast food.

You stand in line while several (let's say 8) cashiers that at the same time are cooks take the orders from the people in front of you.