```Python hl_lines="4  9-12  25-27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):

```Python hl_lines="20"
{!../../docs_src/body_nested_models/tutorial004.py!}
```

これは **FastAPI** が以下のようなボディを期待することを意味します:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2,
    "tags": ["rock", "metal", "bar"],
    "image": {
        "url": "http://example.com/baz.jpg",
        "name": "The Foo live"
    }
}
```

```Python hl_lines="4  9-12  25-27"
from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):

```Python hl_lines="4  9-12  25-27"
from typing import Optional

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):

Avec **FastAPI** vous aurez toutes les fonctionnalités de **Pydantic**  (comme FastAPI est basé sur Pydantic pour toutes les manipulations de données):

* **Pas de prise de tête**:
    * Pas de nouveau langage de définition de schéma à apprendre.
    * Si vous connaissez le typage en python vous savez comment utiliser Pydantic.

 *
 * <p>This class should not be assumed to be universally superior to {@code
 * java.util.LinkedHashSet}. Generally speaking, this class reduces object allocation and memory
 * consumption at the price of moderately increased constant factors of CPU. Only use this class
 * when there is a specific reason to prioritize memory over CPU.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible // not worth using in GWT for now

Vous pouvez ensuite continuer avec les instructions précédentes, pour une "langue existante".

##### Nouvelle langue non prise en charge

Si, lors de l'exécution du script du serveur en direct, vous obtenez une erreur indiquant que la langue n'est pas prise en charge, quelque chose comme :

```
 raise TemplateNotFound(template)
jinja2.exceptions.TemplateNotFound: partials/language/xx.html
```

![editor support](https://fastapi.tiangolo.com/img/pycharm-completion.png)

شما پیشنهاد های تکمیل خودکاری را خواهید گرفت که حتی ممکن است قبلا آن را غیرممکن تصور میکردید. به عنوان مثال کلید `price` در داخل بدنه JSON (که میتوانست تودرتو نیز باشد) که از یک درخواست آمده است.

دیگر خبری از تایپ کلید اشتباهی، برگشتن به مستندات یا پایین بالا رفتن برای فهمیدن اینکه شما از `username` یا `user_name` استفاده کرده اید نیست.

### مختصر

*  `prices` değişkeni `dict` tipindedir:
    *  `dict` değişkeninin `key` değeri  `str` tipindedir (herbir item'ın "name" değeri).
    *  `dict` değişkeninin `value` değeri `float` tipindedir (lherbir item'ın "price" değeri).

#### `Optional`

`Optional` bir değişkenin `str`gibi bir tipi olabileceğini ama isteğe bağlı olarak tipinin `None` olabileceğini belirtir:

```Python hl_lines="1  4"

 *
 * <p>This class should not be assumed to be universally superior to {@code
 * java.util.LinkedHashMap}. Generally speaking, this class reduces object allocation and memory
 * consumption at the price of moderately increased constant factors of CPU. Only use this class
 * when there is a specific reason to prioritize memory over CPU.
 *
 * @author Louis Wasserman
 */