on_event() — fastapi Function Reference

Architecture documentation for the on_event() function in routing.py from the fastapi codebase.

Function python FastAPI Routing calls 1 called by 1

Entity Profile

FastAPI→ Routing→ on_event() — fastapi Function Reference

Dependency Diagram

graph TD
  a27c576c_fb92_8398_f37e_212c576404a2["on_event()"]
  ecadd3bc_0c58_b4e5_06d8_57da79199adc["APIRouter"]
  a27c576c_fb92_8398_f37e_212c576404a2 -->|defined in| ecadd3bc_0c58_b4e5_06d8_57da79199adc
  dac05d36_d298_20ac_8313_653329a27887["on_event()"]
  dac05d36_d298_20ac_8313_653329a27887 -->|calls| a27c576c_fb92_8398_f37e_212c576404a2
  4bbb96be_c308_9252_9434_46c4b5112bf3["add_event_handler()"]
  a27c576c_fb92_8398_f37e_212c576404a2 -->|calls| 4bbb96be_c308_9252_9434_46c4b5112bf3
  style a27c576c_fb92_8398_f37e_212c576404a2 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

fastapi/routing.py lines 4610–4634

    def on_event(
        self,
        event_type: Annotated[
            str,
            Doc(
                """
                The type of event. `startup` or `shutdown`.
                """
            ),
        ],
    ) -> Callable[[DecoratedCallable], DecoratedCallable]:
        """
        Add an event handler for the router.

        `on_event` is deprecated, use `lifespan` event handlers instead.

        Read more about it in the
        [FastAPI docs for Lifespan Events](https://fastapi.tiangolo.com/advanced/events/#alternative-events-deprecated).
        """

        def decorator(func: DecoratedCallable) -> DecoratedCallable:
            self.add_event_handler(event_type, func)
            return func

        return decorator