Muti-list merge in Python

from heapq import heappush, heappop

alist = []

l = [('A',1),('B',2),('F',6)]
alist.append(l)

l = [('C',3),('D',4),('H',8)]
alist.append(l)

l = [('E',5),('G',7)]
alist.append(l)

#print alist


heap = []

index = 0
for lst in alist:
    if lst:
        item = lst.pop(0);
        heappush(heap, (item, index))
    index = index + 1
   
while heap:
    ituple =  heappop(heap)
    item = ituple[0]
    index = ituple[1]
    lst = alist[index]
    if lst:
        newitem = lst.pop(0)
        heappush(heap, (newitem, index))

    print item