inputs = [
  itertools.count(),
  [2, 4, 6],
  [100, 101, 1000],
  []]

def multisort(inputs):
   outs = [[None, input] for input in inputs]
   while True:
      for out in outs:
        if out[0] is None: out[0] = out[1].next()
      outs = sorted(outs) # prob need to sort by 1st elt specifically
      yield outs[0][0]
      outs[0][0] = None
      ...



   while True:
     # make sure we have the next value from each iterator
     for i in xrange(0, len(inputs):
        if last[i] is None:
           last[i] = inputs[i].next()

     # find the smallest value in last
     # yield it and replace it with None
     small_index = None
     small_value = None
     for i in xrange(0, len(inputs)):
       if small_index is None or last[i] < small_value:
          small_index = i
	  small_value = last[i]
    yield last[i]
    last[i] = None

for i in multisort(inputs):
  print i

# prints 0 1 2 3 4 5 6 100 101 1000