3. El dataclass `Author` incluye una lista de dataclasses `Item`.

4. El dataclass `Author` se usa como el parámetro `response_model`.

5. Puedes usar otras anotaciones de tipos estándar con dataclasses como el request body.

    En este caso, es una lista de dataclasses `Item`.

6. Aquí estamos regresando un diccionario que contiene `items`, que es una lista de dataclasses.

  private void testItems() {
    for (Object item : Iterables.concat(equalityGroups)) {
      assertTrue(item + " must not be Object#equals to null", !item.equals(null));
      assertTrue(
          item + " must not be Object#equals to an arbitrary object of another class",
          !item.equals(NotAnInstance.EQUAL_TO_NOTHING));
      assertTrue(item + " must be Object#equals to itself", item.equals(item));
      assertEquals(

        return encoded_dict
    if isinstance(obj, (list, set, frozenset, GeneratorType, tuple, deque)):
        encoded_list = []
        for item in obj:
            encoded_list.append(
                jsonable_encoder(
                    item,
                    include=include,
                    exclude=exclude,
                    by_alias=by_alias,
                    exclude_unset=exclude_unset,

        from pydantic import BaseModel

        class Item(BaseModel):
            name: str
            description: str | None = None

        app = FastAPI()
        router = APIRouter()

        @router.put("/items/{item_id}")
        def replace_item(item_id: str, item: Item):
            return {"message": "Item replaced", "id": item_id}

        app.include_router(router)

from typing import Annotated

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_items(
    *,
    item_id: Annotated[int, Path(title="The ID of the item to get", ge=0, le=1000)],
    q: str,
    size: Annotated[float, Query(gt=0, lt=10.5)],
):
    results = {"item_id": item_id}
    if q:
        results.update({"q": q})
    if size:
        results.update({"size": size})

///

Eso significa: "la variable `items` es una `list`, y cada uno de los ítems en esta lista es un `str`".

Al hacer eso, tu editor puede proporcionar soporte incluso mientras procesa elementos de la lista:

<img src="/img/python-types/image05.png">

Sin tipos, eso es casi imposible de lograr.

Nota que la variable `item` es uno de los elementos en la lista `items`.

	VersionID string `xml:"VersionId"`
}

// Metadata metadata items implemented to ensure XML marshaling works.
type Metadata struct {
	Items []struct {
		Key   string
		Value string
	}
}

// Set add items, duplicate items get replaced.
func (s *Metadata) Set(k, v string) {
	for i, item := range s.Items {
		if item.Key == k {
			s.Items[i] = struct {
				Key   string
				Value string
			}{

* look for the subpackage `routers` (the directory at `app/routers/`)...
* and from it, import the submodule `items` (the file at `app/routers/items.py`) and `users` (the file at `app/routers/users.py`)...

The module `items` will have a variable `router` (`items.router`). This is the same one we created in the file `app/routers/items.py`, it's an `APIRouter` object.

And then we do the same for the module `users`.

## FastAPI App with Tags { #fastapi-app-with-tags }

In many cases, your FastAPI app will be bigger, and you will probably use tags to separate different groups of *path operations*.

For example, you could have a section for **items** and another section for **users**, and they could be separated by tags:

{* ../../docs_src/generate_clients/tutorial002_py39.py hl[21,26,34] *}

        raise


@app.get("/items/{item_id}")
def get_item(item_id: str, username: str = Depends(get_username)):
    if item_id == "portal-gun":
        raise InternalError(
            f"The portal gun is too dangerous to be owned by {username}"
        )
    if item_id != "plumbus":
        raise HTTPException(
            status_code=404, detail="Item not found, there's only a plumbus here"
        )