<blockquote markdown="1">

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

I have been avoiding the creation of a new framework for several years. First I tried to solve all the features covered by **FastAPI** using many different frameworks, plug-ins, and tools.

///

/// check | "A inspiré **FastAPI** à"

Hug a inspiré certaines parties d'APIStar, et était l'un des outils que je trouvais les plus prometteurs, à côté d'APIStar.

Hug a contribué à inspirer **FastAPI** pour utiliser les type hints Python
pour déclarer les paramètres, et pour générer automatiquement un schéma définissant l'API.

The `TestClient` does some magic inside to call the asynchronous FastAPI application in your normal `def` test functions, using standard pytest. But that magic doesn't work anymore when we're using it inside asynchronous functions. By running our tests asynchronously, we can no longer use the `TestClient` inside our test functions.

Because it's a Python exception, you don't `return` it, you `raise` it.

You write standard Python with types:

```Python
from datetime import date

from pydantic import BaseModel

# Declare a variable as a str
# and get editor support inside the function
def main(user_id: str):
    return user_id


# A Pydantic model
class User(BaseModel):
    id: int
    name: str
    joined: date
```

That can then be used like:

```Python

<blockquote markdown="1">

**FastAPI** não existiria se não pelo trabalho anterior de outros.

Há muitas ferramentas criadas antes que ajudaram a inspirar sua criação.

Eu estive evitando a criação de um novo _framework_ por vários anos. Primeiro tentei resolver todas as funcionalidades cobertas por **FastAPI** usando muitos _frameworks_, _plug-ins_ e ferramentas diferentes.

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`:

{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## Add the background task

Inside of your *path operation function*, pass your task function to the *background tasks* object with the method `.add_task()`:

{* ../../docs_src/background_tasks/tutorial001.py hl[14] *}

`.add_task()` receives as arguments:

Or you might have any other way to communicate with the WebSocket endpoint.

---

But for this example, we'll use a very simple HTML document with some JavaScript, all inside a long string.

This, of course, is not optimal and you wouldn't use it for production.

In production you would have one of the options above.

If you used to rely on this behavior, now you should create the resources for background tasks inside the background task itself, and use internally only data that doesn't depend on the resources of dependencies with `yield`.

* Use the `templates` you created to render and return a `TemplateResponse`, pass the name of the template, the request object, and a "context" dictionary with key-value pairs to be used inside of the Jinja2 template.

```Python hl_lines="4  11  15-18"
{!../../docs_src/templates/tutorial001.py!}
```

/// note

Before FastAPI 0.108.0, Starlette 0.29.0, the `name` was the first parameter.