convert loop to list comprehension

[Paul Rubin]

Paul Rubin <http://phr.cx@NOSPAM.invalid> writes:
> > Question is, can I do this as a list comprehension?
> 
> import operator
> x = reduce(operator.add, ([i]*a for i,a in enumerate(seq)), [])

Maybe more in the iterative spirit:

 import itertools
 seq = [2, 3, 1, 9]
 x = itertools.chain(*([i]*a for i,a in enumerate(seq)))