FastAPI Class — fastapi Architecture

Architecture documentation for the FastAPI class in applications.py from the fastapi codebase.

Class python FastAPI

Entity Profile

FastAPI→ FastAPI Class — fastapi Architecture

Dependency Diagram

graph TD
  587454b3_6db6_011f_9fa4_3e4e2e09b72d["FastAPI"]
  53e07af2_3e5c_ea1f_ee6c_abc9792bf48b["HTTPException"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|extends| 53e07af2_3e5c_ea1f_ee6c_abc9792bf48b
  58bb043a_10d8_c308_5564_225558a63815["RequestValidationError"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|extends| 58bb043a_10d8_c308_5564_225558a63815
  b73e338b_e4cd_2e94_eb5a_5e6ac7b197b0["WebSocketRequestValidationError"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|extends| b73e338b_e4cd_2e94_eb5a_5e6ac7b197b0
  a4e9210e_542f_dbd2_500a_37b56326c1e7["AsyncExitStackMiddleware"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|extends| a4e9210e_542f_dbd2_500a_37b56326c1e7
  6c1867f2_34c4_b2ed_5639_41766e6fd7ce["applications.py"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|defined in| 6c1867f2_34c4_b2ed_5639_41766e6fd7ce
  bef02968_6cae_fc82_e854_8b053afd9655["__init__()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| bef02968_6cae_fc82_e854_8b053afd9655
  0ad508e9_c474_fd89_127a_1e77e78303e4["build_middleware_stack()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| 0ad508e9_c474_fd89_127a_1e77e78303e4
  a9c07abb_aad1_48b4_2dbe_359121a449b2["openapi()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| a9c07abb_aad1_48b4_2dbe_359121a449b2
  c029d7d0_68b4_7ce7_47cc_25c5b9dccd5d["setup()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| c029d7d0_68b4_7ce7_47cc_25c5b9dccd5d
  685cfafc_8748_c8d0_a18b_4be786160320["__call__()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| 685cfafc_8748_c8d0_a18b_4be786160320
  25327e8f_c38b_0b1b_93ba_5cf6834fddb3["add_api_route()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| 25327e8f_c38b_0b1b_93ba_5cf6834fddb3
  17bcf28f_7595_a117_1722_327988604d26["api_route()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| 17bcf28f_7595_a117_1722_327988604d26
  ba33b279_1103_0775_a008_211bf9ab87de["add_api_websocket_route()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| ba33b279_1103_0775_a008_211bf9ab87de
  7c16e84d_2ff5_4884_612a_8f36a61c9299["websocket()"]
  587454b3_6db6_011f_9fa4_3e4e2e09b72d -->|method| 7c16e84d_2ff5_4884_612a_8f36a61c9299

Relationship Graph

Source Code

fastapi/applications.py lines 48–4672

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[
            Optional[list[BaseRoute]],
            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.

                It will be added to the generated OpenAPI (e.g. visible at `/docs`).

                Read more in the
                [FastAPI docs for Metadata and Docs URLs](https://fastapi.tiangolo.com/tutorial/metadata/#metadata-for-api).

                **Example**

                ```python
                from fastapi import FastAPI

                app = FastAPI(title="ChimichangApp")
                ```
                """
            ),
        ] = "FastAPI",
        summary: Annotated[
            Optional[str],
            Doc(
                """
                A short summary of the API.

                It will be added to the generated OpenAPI (e.g. visible at `/docs`).