Use itertools.chain to create a single generator which will yield the values from several generators in sequence.
from itertools import chain
a = (x for x in ['1', '2', '3', '4'])
b = (x for x in ['x', 'y', 'z'])
' '.join(chain(a, b))
Results in:
'1 2 3 4 x y z'
As an alternate constructo...