Verwenden Sie ihn auf die gleiche Weise wie die Klasse `FastAPI`:

```Python hl_lines="6  11  16" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

Sie können sich `APIRouter` als eine „Mini-`FastAPI`“-Klasse vorstellen.

Alle die gleichen Optionen werden unterstützt.

Alle die gleichen `parameters`, `responses`, `dependencies`, `tags`, usw.

!!! tip "Tipp"

I will show you some of the main concepts you should probably keep in mind when deploying a **FastAPI** application (although most of it applies to any other type of web application).

Then set Cookies in it, and then return it:

```Python hl_lines="10-12"
{!../../../docs_src/response_cookies/tutorial001.py!}
```

!!! tip
    Keep in mind that if you return a response directly instead of using the `Response` parameter, FastAPI will return it directly.

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

    ```Python hl_lines="7"
    {!> ../../../docs_src/path_params_numeric_validations/tutorial002.py!}
    ```

But keep in mind that if you use `Annotated`, you won't have this problem, it won't matter as you're not using the function parameter default values for `Query()` or `Path()`.

=== "Python 3.9+"

    ```Python hl_lines="10"

    ```Python hl_lines="10"
    {!> ../../../docs_src/header_params/tutorial002.py!}
    ```

!!! warning
    Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.

## Duplicate headers

It is possible to receive duplicate headers. That means, the same header with multiple values.

```Python hl_lines="18  22"
{!../../../docs_src/additional_responses/tutorial001.py!}
```

!!! note
    Keep in mind that you have to return the `JSONResponse` directly.

!!! info
    The `model` key is not part of OpenAPI.

    **FastAPI** will take the Pydantic model from there, generate the `JSON Schema`, and put it in the correct place.

    Including how to handle lifespan state that can be used in other areas of your code.

## Sub Applications

```

</div>

!!! note
    Polecenie `uvicorn main:app` odnosi się do:

    * `main`: plik `main.py` ("moduł" Python).
    * `app`: obiekt utworzony w pliku `main.py` w lini `app = FastAPI()`.
    * `--reload`: sprawia, że serwer uruchamia się ponownie po zmianie kodu. Używany tylko w trakcie tworzenia oprogramowania.

Na wyjściu znajduje się linia z czymś w rodzaju:

```hl_lines="4"

```Python
name = Column(String)
```

while Pydantic *models* declare the types using `:`, the new type annotation syntax/type hints:

```Python
name: str
```

Keep these in mind, so you don't get confused when using `=` and `:` with them.

### Create Pydantic *models* / schemas for reading / returning

Use it the same way you would use the `FastAPI` class:

```Python hl_lines="6  11  16" title="app/routers/users.py"
{!../../../docs_src/bigger_applications/app/routers/users.py!}
```

You can think of `APIRouter` as a "mini `FastAPI`" class.

All the same options are supported.

All the same `parameters`, `responses`, `dependencies`, `tags`, etc.

!!! tip