Class FastAPI

fastapi/applications.py:42–4768

`FastAPI` app class, the main entrypoint to use FastAPI. Read more in the [FastAPI docs for First Steps](https://fastapi.tiangolo.com/tutorial/first-steps/). ## Example ```python from fastapi import FastAPI app = FastAPI() ```

class FastAPI(Starlette):
    """
    `FastAPI` app class, the main entrypoint to use FastAPI.

    Read more in the
    [FastAPI docs for First Steps](https://fastapi.tiangolo.com/tutorial/first-steps/).

    ## Example

    ```python
    from fastapi import FastAPI

    app = FastAPI()
    ```
    """

    def __init__(
        self: AppType,
        *,
        debug: Annotated[
            bool,
            Doc(
                """
                Boolean indicating if debug tracebacks should be returned on server
                errors.

                Read more in the
                [Starlette docs for Applications](https://www.starlette.dev/applications/#instantiating-the-application).
                """
            ),
        ] = False,
        routes: Annotated[
            list[BaseRoute] | None,
            Doc(
                """
                **Note**: you probably shouldn't use this parameter, it is inherited
                from Starlette and supported for compatibility.

                ---

                A list of routes to serve incoming HTTP and WebSocket requests.
                """
            ),
            deprecated(
                """
                You normally wouldn't use this parameter with FastAPI, it is inherited
                from Starlette and supported for compatibility.

                In FastAPI, you normally would use the *path operation methods*,
                like `app.get()`, `app.post()`, etc.
                """
            ),
        ] = None,
        title: Annotated[
            str,
            Doc(
                """
                The title of the API.