# Without aliases


@app.post("/required-str", operation_id="required_str")
async def read_required_str(p: Annotated[str, Body(embed=True)]):
    return {"p": p}


class BodyModelRequiredStr(BaseModel):
    p: str


@app.post("/model-required-str", operation_id="model_required_str")
async def read_model_required_str(p: BodyModelRequiredStr):
    return {"p": p.p}

@app.get("/required-str")
async def read_required_str(p: Annotated[str, Header()]):
    return {"p": p}


class HeaderModelRequiredStr(BaseModel):
    p: str


@app.get("/model-required-str")
async def read_model_required_str(p: Annotated[HeaderModelRequiredStr, Header()]):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/required-str", "/model-required-str"],
)

| 参数 | 类型 | 描述 |
|------------|------|-------------|
| `title` | `str` | API 的标题。 |
| `summary` | `str` | API 的简短摘要。 <small>自 OpenAPI 3.1.0、FastAPI 0.99.0 起可用。</small> |
| `description` | `str` | API 的简短描述。可以使用 Markdown。 |
| `version` | `string` | API 的版本。这是您自己的应用程序的版本，而不是 OpenAPI 的版本。例如 `2.5.0`。 |
| `terms_of_service` | `str` | API 服务条款的 URL。如果提供，则必须是 URL。 |

      }
      String str = builder.toString();
      HashCode hashUtf8 = murmur3_32().hashBytes(str.getBytes(UTF_8));
      assertEquals(hashUtf8, murmur3_32().newHasher().putBytes(str.getBytes(UTF_8)).hash());
      assertEquals(hashUtf8, murmur3_32().hashString(str, UTF_8));
      assertEquals(hashUtf8, murmur3_32().newHasher().putString(str, UTF_8).hash());

            """
        ),
    ] = None,
    description: Annotated[
        str | None,
        Doc(
            """
            Human-readable description.

            Read more about it in the
            [FastAPI docs about Query parameters](https://fastapi.tiangolo.com/tutorial/query-params-str-validations/#declare-more-metadata)

class Item(BaseModel):
    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,
):

    "path",
    ["/optional-list-str", "/model-optional-list-str"],
)
def test_optional_list_str_missing_empty_dict(path: str):
    client = TestClient(app)
    response = client.post(path, json={})
    assert response.status_code == 200, response.text
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    ["/optional-list-str", "/model-optional-list-str"],
)

    async def lifespan(
        app: FastAPI,
    ) -> AsyncGenerator[dict[str, str | bool], None]:
        yield {
            "app_specific": True,
            "overridden": "app",
        }

    @asynccontextmanager
    async def router_lifespan(
        app: FastAPI,
    ) -> AsyncGenerator[dict[str, str | bool], None]:
        yield {
            "router_specific": True,

```

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`.

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: str | None = None
    scopes: list[str] = []


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


class UserInDB(User):
    hashed_password: str


password_hash = PasswordHash.recommended()