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):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):

stands for one item (parameter or result) of the specified type and
all non-<a href="#Blank_identifier">blank</a> names in the signature
must be <a href="#Uniqueness_of_identifiers">unique</a>.
If absent, each type stands for one item of that type.
Parameter and result
lists are always parenthesized except that if there is exactly
one unnamed result it may be written as an unparenthesized type.

En fait, `FastAPI` est un sous composant de `Starlette`. Donc, si vous savez déjà comment utiliser Starlette, la plupart des fonctionnalités fonctionneront de la même manière.

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[10] *}

/// note

Un paramètre de chemin est toujours requis car il doit faire partie du chemin. Même si vous l'avez déclaré avec `None` ou défini une valeur par défaut, cela ne changerait rien, il serait toujours requis.

///

## Ordonnez les paramètres comme vous le souhaitez

/// tip

    name: Optional[str] = None
    call: Optional[Callable[..., Any]] = None
    request_param_name: Optional[str] = None
    websocket_param_name: Optional[str] = None
    http_connection_param_name: Optional[str] = None
    response_param_name: Optional[str] = None
    background_tasks_param_name: Optional[str] = None
    security_scopes_param_name: Optional[str] = None
    own_oauth_scopes: Optional[list[str]] = None

        default_factory: Union[Callable[[], Any], None] = _Unset,
        annotation: Optional[Any] = None,
        alias: Optional[str] = None,
        alias_priority: Union[int, None] = _Unset,
        validation_alias: Union[str, AliasPath, AliasChoices, None] = None,
        serialization_alias: Union[str, None] = None,
        title: Optional[str] = None,
        description: Optional[str] = None,
        gt: Optional[float] = None,

    name: str
    description: str | None = None
    price: float
    tax: float | None = None


class User(BaseModel):
    username: str
    full_name: str | None = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Item,
    user: User,
    importance: Annotated[int, Body(gt=0)],
    q: str | None = None,
):

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}
    if q:

    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None


class User(BaseModel):
    username: str
    full_name: Union[str, None] = None


@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Item,
    user: User,
    importance: Annotated[int, Body(gt=0)],
    q: Union[str, None] = None,
):

```Python
q: str | None = None
```

////

//// tab | Python 3.8+

```Python
q: Union[str, None] = None
```

////

Тепер ми загорнемо її у `Annotated`, і отримаємо:

//// tab | Python 3.10+

```Python
q: Annotated[str | None] = None
```

////

//// tab | Python 3.8+

```Python
q: Annotated[Union[str, None]] = None
```

////