{!> ../../docs_src/python_types/tutorial008b_py39.py!}
```

////

In both cases this means that `item` could be an `int` or a `str`.

#### Possibly `None` { #possibly-none }

You can declare that a value could have a type, like `str`, but that it could also be `None`.

In Python 3.6 and above (including Python 3.10) you can declare it by importing and using `Optional` from the `typing` module.

```Python hl_lines="1  4"

            200,
            {"q_or_cookie": "foo"},
        ),
        (
            "/items",
            None,
            200,
            {"q_or_cookie": None},
        ),
    ],
)
def test_get(path, cookie, expected_status, expected_response, client: TestClient):
    if cookie is not None:
        client.cookies.set("last_query", cookie)
    else:
        client.cookies.clear()
    response = client.get(path)

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(user_agent: str | None = Header(default=None)):

     * <p>
     * This implementation maintains UTC time to ensure monotonic behavior.
     * The provided zone parameter is ignored.
     *
     * @param zone the target timezone (ignored)
     * @return this clock instance
     */
    @Override
    public Clock withZone(ZoneId zone) {
        // Monotonic clock is always UTC-based
        return this;
    }

		for i := range erasureDisks[:8] {
			erasureDisks[i] = nil
		}
		return erasureDisks
	}
	z.serverPools[0].erasureDisksMu.Unlock()

	t.Run("if-none-match with read quorum failure", func(t *testing.T) {
		// Test Case 1: if-none-match (create only if doesn't exist)
		// With if-none-match: *, this should only succeed if object doesn't exist.
		// Since read quorum fails, we can't determine if object exists.
		opts := ObjectOptions{

from fastapi import FastAPI
from fastapi.openapi.docs import (
    get_redoc_html,
    get_swagger_ui_html,
    get_swagger_ui_oauth2_redirect_html,
)

app = FastAPI(docs_url=None, redoc_url=None)


@app.get("/docs", include_in_schema=False)
async def custom_swagger_ui_html():
    return get_swagger_ui_html(
        openapi_url=app.openapi_url,
        title=app.title + " - Swagger UI",

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(x_token: list[str] | None = Header(default=None)):

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: list[str] | None = Query(default=None)):
    query_items = {"q": q}

    assert response.json() == {
        "item_id": 5,
        "item": {
            "name": "Foo",
            "description": None,
            "price": 35.4,
            "tax": None,
            "tags": [],
            "images": None,
        },
    }


def test_put_empty_body(client: TestClient):
    response = client.put(
        "/items/5",
        json={},
    )

from typing import Annotated

from fastapi import FastAPI, Header

app = FastAPI()


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