There are many ways to do this. None of them avoids looping, technically, although you can easily avoid the "for" syntax.
-- Simple but wastes some memory
c = [i-j for i,j in zip(a,b)]
-- Using itertools.izip (python 2.3)
c = [i-j for i,j in itertools.izip(a,b) ]
-- Generator expression (python 2.4)
c = ( i-j for i,j in itertools.izip(a,b) )
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