gist.py

@celery.task
def add(x, y):
 sleep(5)
 return x + y

(python session)
>>> r = group(add.s(3, 4), add.s(5,7))()
(immediately, without waiting 5 seconds)
>>> r.completed_count()
0
(wait 5+ seconds)
>>> r.completed_count()
0
>>> r.ready()
False
>>> r.get()
[7, 12]
>>> r.ready()
True
>>> r.completed_count()
2