## Decision

We do not use Java serialization.
Instead, we use custom serialization where we explicitly describe how data objects should be serialized and deserialized.

For internal purposes, we use binary formats for their brevity.
We use the `Serializer` abstraction to separate the actual implementation of serialization from its uses.

When sharing data with external tools, we use JSON.

## Status

ACCEPTED

type myInt int

type MyInt int

type Time struct{}

type S struct {
	// Deprecated: use PublicTime.
	Public     *int
	private    *int
	PublicTime Time
}

// Deprecated: use URI.
type URL struct{}

type EmbedURLPtr struct {
	*URL
}

type S2 struct {
	// Deprecated: use T.
	S
	Extra bool
}

var X0 int64

var (
	Y int
	X I
)

type Namer interface {

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

So, you might still need to use Pydantic models.

But if you have a bunch of dataclasses laying around, this is a nice trick to use them to power a web API using FastAPI. 🤓

///

## Dataclasses in `response_model`

You can also use `dataclasses` in the `response_model` parameter:

{* ../../docs_src/dataclasses/tutorial002.py hl[1,7:13,19] *}

@ElementTypesAreNonnullByDefault
public class AsyncEventBus extends EventBus {

  /**
   * Creates a new AsyncEventBus that will use {@code executor} to dispatch events. Assigns {@code
   * identifier} as the bus's name for logging purposes.
   *
   * @param identifier short name for the bus, for logging purposes.
   * @param executor Executor to use to dispatch events. It is the caller's responsibility to shut

        "k3": Item(aliased_name="baz", price=2.0, owner_ids=[1, 2, 3]),
    }


@app.get(
    "/items/valid-exclude-unset", response_model=Item, response_model_exclude_unset=True
)
def get_valid_exclude_unset():
    return Item(aliased_name="valid", price=1.0)


@app.get(
    "/items/coerce-exclude-unset",
    response_model=Item,
    response_model_exclude_unset=True,
)
def get_coerce_exclude_unset():

///

/// info

In this example we use invented custom headers `X-Key` and `X-Token`.

But in real cases, when implementing security, you would get more benefits from using the integrated [Security utilities (the next chapter)](../security/index.md){.internal-link target=_blank}.

///

## Dependencies errors and return values

You can use the same dependency *functions* you use normally.

### Dependency requirements

  optional string scope = 4;

  // namespace is the namespace of the resource being referenced. This field is
  // required when scope is set to "Namespace" and must be unset when scope is set to
  // "Cluster".
  // +optional
  optional string namespace = 5;
}

// IngressClassSpec provides information about the class of an Ingress.
message IngressClassSpec {

Mais vous avez toujours besoin d'utiliser `Path` pour le paramètre de chemin `item_id`. Et vous ne voulez pas utiliser `Annotated` pour une raison quelconque.

Python se plaindra si vous mettez une valeur avec une "défaut" avant une valeur qui n'a pas de "défaut".

Mais vous pouvez les réorganiser, et avoir la valeur sans défaut (le paramètre de requête `q`) en premier.

///

//// tab | `venv`

To create a virtual environment, you can use the `venv` module that comes with Python.

<div class="termy">

```console
$ python -m venv .venv
```

</div>

/// details | What that command means

* `python`: use the program called `python`
* `-m`: call a module as a script, we'll tell it which module next
* `venv`: use the module called `venv` that normally comes installed with Python

When writing request headers, use `header(name, value)` to set the only occurrence of `name` to `value`. If there are existing values, they will be removed before the new value is added. Use `addHeader(name, value)` to add a header without removing the headers already present.