Игорёк

res = []
for i in range(0, len(mylist), 9):
    res.append(mylist[i]*2)

res = [mylist[i] * 2 for i in range(0, len(mylist), 9)]

def getcoordinates(a1, a2):
    return [[x*y for x in a2] for y in a1]

def getcoordinates(a1, a2):
    res = []
    for x in a1:
        tmp = []
        for y in a2:
            tmp.append(x*y)
        res.append(tmp)
    return res