Python+Celery: Chaining jobs?

Question

The Celery documentation suggests that it's a bad idea to have tasks wait on the results of other tasks… But the suggested solution (see “good” heading) leaves a something to be desired. Specifically, there's no clear way of getting the subtask's result back to the caller (also, it's kind of ugly).

So, is there any way of “chaining” jobs, so the caller gets the result of the final job? Eg, to use the add example:

>>> add3 = add.subtask(args=(3, ))
>>> add.delay(1, 2, callback=add3).get()
6
>>>

Alternately, is it OK to return instances of Result? For example:

@task
def add(x, y, callback=None):
    result = x + y
    if callback:
        return subtask(callback).defer(result)
    return result

This would let the result of the “final” job in the chain could be retrived with a simple:

result = add(1, 2, callback=add3).delay()
while isinstance(result, Result):
    result = result.get()
print "result:", result

Answer 1

What you propose would work fine. I don't see any alternative, do you?