preprocess_request() — flask Function Reference

Architecture documentation for the preprocess_request() function in app.py from the flask codebase.

Function python ApplicationCore Scaffolding calls 2 called by 1

Entity Profile

ApplicationCore→ Scaffolding→ preprocess_request() — flask Function Reference

Dependency Diagram

graph TD
  cd857c6c_da43_da88_26ed_c88b074b880a["preprocess_request()"]
  9f8cc56e_d5c4_e7a8_438a_3124c0dd5de5["Flask"]
  cd857c6c_da43_da88_26ed_c88b074b880a -->|defined in| 9f8cc56e_d5c4_e7a8_438a_3124c0dd5de5
  4deafda5_fb07_c30c_ad12_a72767b1a116["full_dispatch_request()"]
  4deafda5_fb07_c30c_ad12_a72767b1a116 -->|calls| cd857c6c_da43_da88_26ed_c88b074b880a
  a89c0022_4807_bf16_9be1_6a66f3c78c9f["ensure_sync()"]
  cd857c6c_da43_da88_26ed_c88b074b880a -->|calls| a89c0022_4807_bf16_9be1_6a66f3c78c9f
  53d45141_828e_ea9a_7cbc_ddf952818e95["blueprint()"]
  cd857c6c_da43_da88_26ed_c88b074b880a -->|calls| 53d45141_828e_ea9a_7cbc_ddf952818e95
  style cd857c6c_da43_da88_26ed_c88b074b880a fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

src/flask/app.py lines 1365–1391

    def preprocess_request(self, ctx: AppContext) -> ft.ResponseReturnValue | None:
        """Called before the request is dispatched. Calls
        :attr:`url_value_preprocessors` registered with the app and the
        current blueprint (if any). Then calls :attr:`before_request_funcs`
        registered with the app and the blueprint.

        If any :meth:`before_request` handler returns a non-None value, the
        value is handled as if it was the return value from the view, and
        further request handling is stopped.
        """
        req = ctx.request
        names = (None, *reversed(req.blueprints))

        for name in names:
            if name in self.url_value_preprocessors:
                for url_func in self.url_value_preprocessors[name]:
                    url_func(req.endpoint, req.view_args)

        for name in names:
            if name in self.before_request_funcs:
                for before_func in self.before_request_funcs[name]:
                    rv = self.ensure_sync(before_func)()

                    if rv is not None:
                        return rv  # type: ignore[no-any-return]

        return None