Class Signature

celery/canvas.py:232–871

Task Signature. Class that wraps the arguments and execution options for a single task invocation. Used as the parts in a :class:`group` and other constructs, or to pass tasks around as callbacks while being compatible with serializers with a strict type subset. Signatures

@abstract.CallableSignature.register
class Signature(dict):
    """Task Signature.

    Class that wraps the arguments and execution options
    for a single task invocation.

    Used as the parts in a :class:`group` and other constructs,
    or to pass tasks around as callbacks while being compatible
    with serializers with a strict type subset.

    Signatures can also be created from tasks:

    - Using the ``.signature()`` method that has the same signature
      as ``Task.apply_async``:

        .. code-block:: pycon

            >>> add.signature(args=(1,), kwargs={'kw': 2}, options={})

    - or the ``.s()`` shortcut that works for star arguments:

        .. code-block:: pycon

            >>> add.s(1, kw=2)

    - the ``.s()`` shortcut does not allow you to specify execution options
      but there's a chaining `.set` method that returns the signature:

        .. code-block:: pycon

            >>> add.s(2, 2).set(countdown=10).set(expires=30).delay()

    Note:
        You should use :func:`~celery.signature` to create new signatures.
        The ``Signature`` class is the type returned by that function and
        should be used for ``isinstance`` checks for signatures.

    See Also:
        :ref:`guide-canvas` for the complete guide.

    Arguments:
        task (Union[Type[celery.app.task.Task], str]): Either a task
            class/instance, or the name of a task.
        args (Tuple): Positional arguments to apply.
        kwargs (Dict): Keyword arguments to apply.
        options (Dict): Additional options to :meth:`Task.apply_async`.

    Note:
        If the first argument is a :class:`dict`, the other
        arguments will be ignored and the values in the dict will be used
        instead::

            >>> s = signature('tasks.add', args=(2, 2))
            >>> signature(s)
            {'task': 'tasks.add', args=(2, 2), kwargs={}, options={}}
    """

    TYPES = {}