**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

### Concurrent Burgers

You go with your crush to get fast food, you stand in line while the cashier takes the orders from the people in front of you. 😍

For example, if you need to store it in a database.

For that, **FastAPI** provides a `jsonable_encoder()` function.

## Using the `jsonable_encoder`

Let's imagine that you have a database `fake_db` that only receives JSON compatible data.

For example, it doesn't receive `datetime` objects, as those are not compatible with JSON.

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial001.py!}
```

### Edite-o

É um programa muito simples.

Mas agora imagine que você estava escrevendo do zero.

Em algum momento você teria iniciado a definição da função, já tinha os parâmetros prontos ...

Mas então você deve chamar "esse método que converte a primeira letra em maiúscula".

But there are specific cases where it's useful to get the `Request` object.

## Use the `Request` object directly

Let's imagine you want to get the client's IP address/host inside of your *path operation function*.

For that you need to access the request directly.

```Python hl_lines="1  7-8"

        companies, or even industries — utilities useful for a sizable proportion of all Java
        programmers everywhere. If you can give enough detail such that any of us can imagine coming
        across a similar need in our own work, that's extremely helpful in studying how broadly
        useful the proposed change will be.

  - type: textarea
    attributes:
      label: Concrete Use Cases

**Concorrência** e **paralelismo** ambos são relacionados a "diferentes coisas acontecendo mais ou menos ao mesmo tempo".

Mas os detalhes entre *concorrência* e *paralelismo* são bem diferentes.

Para ver essa diferença, imagine a seguinte história sobre hambúrgueres:

### Hambúrgueres concorrentes

Você vai com seu _crush_ :heart_eyes: na lanchonete, fica na fila enquanto o caixa pega os pedidos das pessoas na sua frente.

**Concurrencia** y **paralelismo** ambos se relacionan con "cosas diferentes que suceden más o menos al mismo tiempo".

Pero los detalles entre *concurrencia* y *paralelismo* son bastante diferentes.

Para entender las diferencias, imagina la siguiente historia sobre hamburguesas:

### Hamburguesas Concurrentes

Vas con la persona que te gusta 😍 a pedir comida rápida 🍔, haces cola mientras el cajero 💁 recoge los pedidos de las personas de delante tuyo.

Pero en algunos casos necesitas retornar un status code diferente al predeterminado.

## Casos de uso

Por ejemplo, imagina que quieres retornar un HTTP status code de "OK" `200` por defecto.

Pero si los datos no existen, quieres crearlos y retornar un HTTP status code de "CREATED" `201`.

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.

Let's look at how we can make that work.

All the dependencies we have seen are a fixed function or class.

But there could be cases where you want to be able to set parameters on the dependency, without having to declare many different functions or classes.

Let's imagine that we want to have a dependency that checks if the query parameter `q` contains some fixed content.

But we want to be able to parameterize that fixed content.

## A "callable" instance