```

////

#### ⚙️ `Union` ⚖️ `Optional`

🚥 👆 ⚙️ 🐍 ⏬ 🔛 3️⃣.1️⃣0️⃣, 📥 💁‍♂ ⚪️➡️ 👇 📶 **🤔** ☝ 🎑:

* 👶 ❎ ⚙️ `Optional[SomeType]`
* ↩️ 👶 **⚙️ `Union[SomeType, None]`** 👶.

👯‍♂️ 🌓 & 🔘 👫 🎏, ✋️ 👤 🔜 👍 `Union` ↩️ `Optional` ↩️ 🔤 "**📦**" 🔜 😑 🔑 👈 💲 📦, & ⚫️ 🤙 ⛓ "⚫️ 💪 `None`", 🚥 ⚫️ 🚫 📦 & ✔.

👤 💭 `Union[SomeType, None]` 🌖 🔑 🔃 ⚫️❔ ⚫️ ⛓.

```Python hl_lines="7"
{!> ../../docs_src/query_params_str_validations/tutorial001_py310.py!}
```

////

🔢 🔢 `q` 🆎 `Union[str, None]` (⚖️ `str | None` 🐍 3️⃣.1️⃣0️⃣), 👈 ⛓ 👈 ⚫️ 🆎 `str` ✋️ 💪 `None`, & 👐, 🔢 💲 `None`, FastAPI 🔜 💭 ⚫️ 🚫 ✔.

/// note

FastAPI 🔜 💭 👈 💲 `q` 🚫 ✔ ↩️ 🔢 💲 `= None`.

 `Union` `Union[str, None]` 🔜 ✔ 👆 👨‍🎨 🤝 👆 👍 🐕‍🦺 & 🔍 ❌.

///

## 🌖 🔬

from typing import Union

from fastapi import Body, FastAPI
from pydantic import BaseModel, Field

app = FastAPI()


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


@app.put("/items/{item_id}")

```

////

## `Union` ⚖️ `anyOf`

👆 💪 📣 📨 `Union` 2️⃣ 🆎, 👈 ⛓, 👈 📨 🔜 🙆 2️⃣.

⚫️ 🔜 🔬 🗄 ⏮️ `anyOf`.

👈, ⚙️ 🐩 🐍 🆎 🔑 <a href="https://docs.python.org/3/library/typing.html#typing.Union" class="external-link" target="_blank">`typing.Union`</a>:

/// note

from typing import Annotated, Union

from fastapi import Body, FastAPI
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,
    item: Annotated[
        Item,
        Body(
            examples=[

from typing import Annotated, Union

from fastapi import Body, FastAPI, status
from fastapi.responses import JSONResponse

app = FastAPI()

items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "size": 3}}


@app.put("/items/{item_id}")
async def upsert_item(
    item_id: str,
    name: Annotated[Union[str, None], Body()] = None,
    size: Annotated[Union[int, None], Body()] = None,
):
    if item_id in items:

from typing import Union

from fastapi import Body, FastAPI
from pydantic import BaseModel, Field
from typing_extensions import Annotated

app = FastAPI()


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

from typing import Union

from fastapi import Body, FastAPI, status
from fastapi.responses import JSONResponse
from typing_extensions import Annotated

app = FastAPI()

items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "size": 3}}


@app.put("/items/{item_id}")
async def upsert_item(
    item_id: str,
    name: Annotated[Union[str, None], Body()] = None,
    size: Annotated[Union[int, None], Body()] = None,
):

from typing import Union


def say_hi(name: Union[str, None] = None):
    if name is not None:
        print(f"Hey {name}!")
    else:

from typing import Union

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(
    strange_header: Union[str, None] = Header(default=None, convert_underscores=False),
):