register() — flask Function Reference

Q: What does register() do?

register() is a function in the flask codebase, defined in src/flask/sansio/blueprints.py.

Q: Where is register() defined?

register() is defined in src/flask/sansio/blueprints.py at line 273.

Q: What does register() call?

register() calls 4 function(s): _merge_blueprint_funcs, add_url_rule, get, make_setup_state.

Architecture documentation for the register() function in blueprints.py from the flask codebase.

Function python ApplicationCore Scaffolding calls 4

Entity Profile

ApplicationCore→ Scaffolding→ register() — flask Function Reference

Dependency Diagram

graph TD
  ab08d213_c111_86c1_e5b9_dd3fd7770d86["register()"]
  0c59fa87_9a90_f011_4207_98ae96479921["Blueprint"]
  ab08d213_c111_86c1_e5b9_dd3fd7770d86 -->|defined in| 0c59fa87_9a90_f011_4207_98ae96479921
  332767b5_f33c_7d07_a9d2_9d9efe7f8c22["make_setup_state()"]
  ab08d213_c111_86c1_e5b9_dd3fd7770d86 -->|calls| 332767b5_f33c_7d07_a9d2_9d9efe7f8c22
  fcb19d5b_9453_b002_936c_db0309530b8c["_merge_blueprint_funcs()"]
  ab08d213_c111_86c1_e5b9_dd3fd7770d86 -->|calls| fcb19d5b_9453_b002_936c_db0309530b8c
  cd459c23_b1c5_45ac_a393_26c2ff268367["get()"]
  ab08d213_c111_86c1_e5b9_dd3fd7770d86 -->|calls| cd459c23_b1c5_45ac_a393_26c2ff268367
  a095b8ad_24db_e31f_c7dd_d94b4dc565d0["add_url_rule()"]
  ab08d213_c111_86c1_e5b9_dd3fd7770d86 -->|calls| a095b8ad_24db_e31f_c7dd_d94b4dc565d0
  style ab08d213_c111_86c1_e5b9_dd3fd7770d86 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

src/flask/sansio/blueprints.py lines 273–377

    def register(self, app: App, options: dict[str, t.Any]) -> None:
        """Called by :meth:`Flask.register_blueprint` to register all
        views and callbacks registered on the blueprint with the
        application. Creates a :class:`.BlueprintSetupState` and calls
        each :meth:`record` callback with it.

        :param app: The application this blueprint is being registered
            with.
        :param options: Keyword arguments forwarded from
            :meth:`~Flask.register_blueprint`.

        .. versionchanged:: 2.3
            Nested blueprints now correctly apply subdomains.

        .. versionchanged:: 2.1
            Registering the same blueprint with the same name multiple
            times is an error.

        .. versionchanged:: 2.0.1
            Nested blueprints are registered with their dotted name.
            This allows different blueprints with the same name to be
            nested at different locations.

        .. versionchanged:: 2.0.1
            The ``name`` option can be used to change the (pre-dotted)
            name the blueprint is registered with. This allows the same
            blueprint to be registered multiple times with unique names
            for ``url_for``.
        """
        name_prefix = options.get("name_prefix", "")
        self_name = options.get("name", self.name)
        name = f"{name_prefix}.{self_name}".lstrip(".")

        if name in app.blueprints:
            bp_desc = "this" if app.blueprints[name] is self else "a different"
            existing_at = f" '{name}'" if self_name != name else ""

            raise ValueError(
                f"The name '{self_name}' is already registered for"
                f" {bp_desc} blueprint{existing_at}. Use 'name=' to"
                f" provide a unique name."
            )

        first_bp_registration = not any(bp is self for bp in app.blueprints.values())
        first_name_registration = name not in app.blueprints

        app.blueprints[name] = self
        self._got_registered_once = True
        state = self.make_setup_state(app, options, first_bp_registration)

        if self.has_static_folder:
            state.add_url_rule(
                f"{self.static_url_path}/<path:filename>",
                view_func=self.send_static_file,  # type: ignore[attr-defined]
                endpoint="static",
            )

        # Merge blueprint data into parent.
        if first_bp_registration or first_name_registration:
            self._merge_blueprint_funcs(app, name)

        for deferred in self.deferred_functions:
            deferred(state)

        cli_resolved_group = options.get("cli_group", self.cli_group)

        if self.cli.commands:
            if cli_resolved_group is None:
                app.cli.commands.update(self.cli.commands)
            elif cli_resolved_group is _sentinel:
                self.cli.name = name
                app.cli.add_command(self.cli)
            else:
                self.cli.name = cli_resolved_group
                app.cli.add_command(self.cli)

        for blueprint, bp_options in self._blueprints:
            bp_options = bp_options.copy()
            bp_url_prefix = bp_options.get("url_prefix")
            bp_subdomain = bp_options.get("subdomain")