client = TestClient(app)


class Item(BaseModel):
    data: str


def duplicate_dependency(item: Item):
    return item


def dependency(item2: Item):
    return item2


def sub_duplicate_dependency(
    item: Item, sub_item: Item = Depends(duplicate_dependency)
):
    return [item, sub_item]


@app.post("/with-duplicates")

                    },
                    "summary": "Update Item",
                },
            },
        },
        "components": {
            "schemas": {
                "Body_update_item_items__item_id__put": {
                    "properties": {
                        "item": {
                            "$ref": "#/components/schemas/Item",
                        },
                        "user": {

from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: Optional[str] = None


class ExtendedItem(Item):
    age: int


@app.post("/items/")
def save_union_different_body(item: Union[ExtendedItem, Item]):
    return {"item": item}


client = TestClient(app)


def test_post_extended_item():

            "tags": [],
            "tax": None,
        },
    ]


def test_create_item(client: TestClient):
    item_data = {
        "name": "Test Item",
        "description": "A test item",
        "price": 10.5,
        "tax": 1.5,
        "tags": ["test", "item"],
    }
    response = client.post("/items/", json=item_data)
    assert response.status_code == 200, response.text
    assert response.json() == item_data

                    },
                    "summary": "Create an item",
                    "description": "Create an item with all the information:\n\n- **name**: each item must have a name\n- **description**: a long description\n- **price**: required\n- **tax**: if the item doesn't have tax, you can omit this\n- **tags**: a set of unique tag strings for this item",
                    "operationId": "create_item_items__post",

    size: Union[int, None] = Body(default=None),
):
    if item_id in items:
        item = items[item_id]
        item["name"] = name
        item["size"] = size
        return item
    else:
        item = {"name": name, "size": size}
        items[item_id] = item

from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int = Path(title="The ID of the item to get", ge=0, le=1000),
    q: Union[str, None] = None,
    item: Union[Item, None] = None,
):
    results = {"item_id": item_id}

Supongamos que solo tienes un único parámetro de cuerpo `item` de un modelo Pydantic `Item`.

Por defecto, **FastAPI** esperará su cuerpo directamente.

Pero si deseas que espere un JSON con una clave `item` y dentro de ella los contenidos del modelo, como lo hace cuando declaras parámetros de cuerpo extra, puedes usar el parámetro especial `Body` `embed`:

```Python
item: Item = Body(embed=True)
```

como en:

<div class="announce-wrapper">
  <div id="announce-left">
    <div class="item">
      <a class="announce-link" href="https://fastapicloud.com" target="_blank">
        <span class="twemoji">
          {% include ".icons/material/cloud-arrow-up.svg" %}
        </span> Join the <strong>FastAPI Cloud</strong> waiting list 🚀
      </a>
    </div>
    <div class="item">
      <a class="announce-link" href="https://x.com/fastapi" target="_blank">

}


@app.get("/items/{item_id}", response_model=Item)
async def read_item(item_id: str):
    return items[item_id]


@app.patch("/items/{item_id}", response_model=Item)
async def update_item(item_id: str, item: Item):
    stored_item_data = items[item_id]
    stored_item_model = Item(**stored_item_data)
    update_data = item.model_dump(exclude_unset=True)