Method _prepared

celery/canvas.py:1693–1740

Recursively unroll the group into a generator of its tasks. This is used by :meth:`apply_async` and :meth:`apply` to unroll the group into a list of tasks that can be evaluated. Note: This does not change the group itself, it only returns a generator

(self, tasks, partial_args, group_id, root_id, app,
                  CallableSignature=abstract.CallableSignature,
                  from_dict=Signature.from_dict,
                  isinstance=isinstance, tuple=tuple)

        return tuple(child_task.link_error(sig.clone(immutable=True)) for child_task in self.tasks)

    def _prepared(self, tasks, partial_args, group_id, root_id, app,
                  CallableSignature=abstract.CallableSignature,
                  from_dict=Signature.from_dict,
                  isinstance=isinstance, tuple=tuple):
        """Recursively unroll the group into a generator of its tasks.

        This is used by :meth:`apply_async` and :meth:`apply` to
        unroll the group into a list of tasks that can be evaluated.

        Note:
            This does not change the group itself, it only returns
            a generator of the tasks that the group would evaluate to.

        Arguments:
            tasks (list): List of tasks in the group (may contain nested groups).
            partial_args (list): List of arguments to be prepended to
                the arguments of each task.
            group_id (str): The group id of the group.
            root_id (str): The root id of the group.
            app (Celery): The Celery app instance.
            CallableSignature (class): The signature class of the group's tasks.
            from_dict (fun): Function to create a signature from a dict.
            isinstance (fun): Function to check if an object is an instance
                of a class.
            tuple (class): A tuple-like class.

        Returns:
            generator: A generator for the unrolled group tasks.
                The generator yields tuples of the form ``(task, AsyncResult, group_id)``.
        """
        for index, task in enumerate(tasks):
            if isinstance(task, CallableSignature):
                # local sigs are always of type Signature, and we
                # clone them to make sure we don't modify the originals.
                task = task.clone()
            else:
                # serialized sigs must be converted to Signature.
                task = from_dict(task, app=app)
            if isinstance(task, group):
                # needs yield_from :(
                unroll = task._prepared(
                    task.tasks, partial_args, group_id, root_id, app,
                )
                yield from unroll
            else:
                if partial_args and not task.immutable:
                    task.args = tuple(partial_args) + tuple(task.args)
                yield task, task.freeze(group_id=group_id, root_id=root_id, group_index=index), group_id

    def _apply_tasks(self, tasks, producer=None, app=None, p=None,
                     add_to_parent=None, chord=None,