## !!
## Talla saa 1+4+7 keskiarvon
#i=0
#j=0
#sum_intensity=0
#list_of_average_intensities = []
#number_of_pictures = 3
#intensities=[1,2,3,4,5,6,7,8,9]
#for i in range(len(intensities)):
#    if i%number_of_pictures == 0:
#        sum_intensity = sum_intensity + intensities[i]
#average_intensity = sum_intensity/number_of_pictures
#list_of_average_intensities.append(average_intensity)
#print list_of_average_intensities

## Nyt mietit, miten saat listaan 2+5+8 ja 3+6+9

def flatten(l, ltypes=(list, tuple)):
    ltype = type(l)
    l = list(l)
    i = 0
    while i < len(l):
        while isinstance(l[i], ltypes):
            if not l[i]:
                l.pop(i)
                i -= 1
                break
            else:
                l[i:i + 1] = l[i]
        i += 1
    return ltype(l)


i=0
j=0
sum_intensity=0
list_of_average_intensities = []
number_of_pictures = 3
intensities=[1,2,3,4,5,6,7,8,9]
intensities = flatten(intensities)
for i in range(number_of_pictures):
    for j in range(i,len(intensities), number_of_pictures):
            sum_intensity = sum_intensity + intensities[j]
    average_intensity = sum_intensity/number_of_pictures
    list_of_average_intensities.append(average_intensity)
    sum_intensity = 0
print list_of_average_intensities