from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


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

    model_config = {
        "json_schema_extra": {
            "examples": [
                {
                    "name": "Foo",
                    "description": "A very nice Item",
                    "price": 35.4,

例えば、`str` または `None` になり得ることを宣言できます:

```python
from typing import Union


def say_hi(name: Union[str, None]):
        print(f"Hi {name}!")
```

`typing` には、`None` を取り得ることを宣言するための短縮形として `Optional` もあります。

ここからは私のとても主観的な提案です:

- 🚨 `Optional[SomeType]` の使用は避けましょう
- 代わりに ✨ **`Union[SomeType, None]` を使いましょう** ✨。

app = FastAPI()


@app.post("/files/")
async def create_file(file: Annotated[bytes | None, File()] = None):
    if not file:
        return {"message": "No file sent"}
    else:
        return {"file_size": len(file)}


@app.post("/uploadfile/")
async def create_upload_file(file: UploadFile | None = None):
    if not file:
        return {"message": "No upload file sent"}
    else:

type lazyInit struct {
	done uint32
	m    sync.Mutex
}

func (l *lazyInit) Do(f func() error) error {
	if atomic.LoadUint32(&l.done) == 0 {
		return l.doSlow(f)
	}
	return nil
}

func (l *lazyInit) doSlow(f func() error) error {
	l.m.Lock()
	defer l.m.Unlock()
	if atomic.LoadUint32(&l.done) == 0 {
		if err := f(); err != nil {
			return err
		}

from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = Field(
        default=None, title="The description of the item", max_length=300
    )
    price: float = Field(gt=0, description="The price must be greater than zero")
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):

func (m *muxServer) handleInbound(c *Connection, inbound <-chan []byte, handlerIn chan<- []byte) {
	for {
		select {
		case <-m.ctx.Done():
			return
		case in, ok := <-inbound:
			if !ok {
				return
			}
			select {
			case <-m.ctx.Done():
				return
			case handlerIn <- in:
				m.send(message{Op: OpUnblockClMux, MuxID: m.ID, Flags: c.baseFlags})
			}
		}
	}
}

    [
        "array",
        ["string", "null"],
        None,
    ],
)
def test_allowed_schema_type(
    type_value: SchemaType | list[SchemaType] | None,
) -> None:
    """Test that Schema accepts SchemaType, List[SchemaType] and None for type field."""
    schema = Schema(type=type_value)
    assert schema.type == type_value


def test_invalid_type_value() -> None:

Paul Merlin <******@****.***> <******@****.***>
Peter Niederwieser <******@****.***> <pniederw@.(none)>
Peter Niederwieser <******@****.***> <pniederw@pniederw-PC.(none)>
Piotr Jagielski <******@****.***> <Piotr Jagielski>
Rene Groeschke <******@****.***> <Rene@DevWin7.(none)>
Rene Groeschke <******@****.***> <******@****.***>
Rene Groeschke <******@****.***> <******@****.***>

        return str(obj)
    if isinstance(obj, (str, int, float, type(None))):
        return obj
    if isinstance(obj, PydanticUndefinedType):
        return None
    if isinstance(obj, dict):
        encoded_dict = {}
        allowed_keys = set(obj.keys())
        if include is not None:
            allowed_keys &= set(include)
        if exclude is not None:
            allowed_keys -= set(exclude)

```mermaid
flowchart LR
    subgraph global[global env]
        harry-1[harry v1]
    end
    subgraph stone-project[philosophers-stone project]
        stone(philosophers-stone) -->|requires| harry-1
    end
```