xRange = 4
yRange = 3
baseList = []
values = []
count = 0

#make a list of 100 values
for i in range(100):
    values.append(i)

#add 4 lists to base list
for x in range(xRange):
    baseList.append([])
#at this point i have [[], [], [], []]

#add 3 values to all 4 lists
for x in range(xRange):
        for y in range(yRange):
            baseList[x].append(values[count])
            count += 1

print baseList

#the result i'm expecting is:
#[[0,1,2], [3,4,5], [6,7,8], [9,10,11]]