!!! tip
        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="4"
    {!> ../../../docs_src/body_fields/tutorial001.py!}
    ```

!!! warning
    Notice that `Field` is imported directly from `pydantic`, not from `fastapi` as are all the rest (`Query`, `Path`, `Body`, etc).

## Declare model attributes

You can then use `Field` with model attributes:

=== "Python 3.10+"

* New [WebSocketException (and docs)](https://fastapi.tiangolo.com/advanced/websockets/#using-depends-and-others), re-exported from Starlette.
* Upgraded and relaxed dependencies for package extras `all` (including new Uvicorn version), when you install `"fastapi[all]"`.

We are importing the submodule `items` directly, instead of importing just its variable `router`.

This is because we also have another variable named `router` in the submodule `users`.

If we had imported one after the other, like:

```Python
from .routers.items import router
from .routers.users import router
```

    ```Python hl_lines="1"
    {!> ../../../docs_src/python_types/tutorial006.py!}
    ```

    Declare the variable, with the same colon (`:`) syntax.

    As the type, put the `List` that you imported from `typing`.

    As the list is a type that contains some internal types, you put them in square brackets:

    ```Python hl_lines="4"
    {!> ../../../docs_src/python_types/tutorial006.py!}
    ```

你还可能有**其他原因**，这将使你更容易拥有一个带有**多个进程**的**单个容器**，而不是拥有每个容器中都有**单个进程**的**多个容器**。

例如（取决于你的设置）你可以在同一个容器中拥有一些工具，例如 Prometheus exporter，该工具应该有权访问**每个请求**。

在这种情况下，如果你有**多个容器**，默认情况下，当 Prometheus 来**读取metrics**时，它每次都会获取**单个容器**的metrics（对于处理该特定请求的容器），而不是获取所有复制容器的**累积metrics**。

在这种情况， 这种做法会更加简单：让**一个容器**具有**多个进程**，并在同一个容器上使用本地工具（例如 Prometheus exporter）收集所有内部进程的 Prometheus 指标并公开单个容器上的这些指标。

---

We also declare a special parameter of type `SecurityScopes`, imported from `fastapi.security`.

This `SecurityScopes` class is similar to `Request` (`Request` was used to get the request object directly).

=== "Python 3.10+"

    ```Python hl_lines="8  105"

::: fastapi.middleware.cors.CORSMiddleware

It can be imported from `fastapi`:

```python
from fastapi.middleware.cors import CORSMiddleware
```

::: fastapi.middleware.gzip.GZipMiddleware

It can be imported from `fastapi`:

```python
from fastapi.middleware.gzip import GZipMiddleware
```

::: fastapi.middleware.httpsredirect.HTTPSRedirectMiddleware

It can be imported from `fastapi`:

```python

You can use:

* `HTTPException`
* `WebSocketException`

These exceptions can be imported directly from `fastapi`:

```python
from fastapi import HTTPException, WebSocketException
```

::: fastapi.HTTPException

We name it `SessionLocal` to distinguish it from the `Session` we are importing from SQLAlchemy.

We will use `Session` (the one imported from SQLAlchemy) later.

To create the `SessionLocal` class, use the function `sessionmaker`:

```Python hl_lines="11"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

## Technical Details

The class `BackgroundTasks` comes directly from <a href="https://www.starlette.io/background/" class="external-link" target="_blank">`starlette.background`</a>.

It is imported/included directly into FastAPI so that you can import it from `fastapi` and avoid accidentally importing the alternative `BackgroundTask` (without the `s` at the end) from `starlette.background`.