from itertools import cycle
letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l']

#2d-array initialization
width, height = 3, 6
repRange = cycle(range(1, 3))
values = [0] * (width - 1)
array2d = [[next(repRange)] + values for y in range(height)]

#Filling array with letters:
m = 0
for i in range(height):
    for j in range(1,width):
       array2d[i][j] = letters[m]
       m+=1

#Printing:
for row in array2d:
    print(row)

[1, 'a', 'b']
[2, 'c', 'd']
[1, 'e', 'f']
[2, 'g', 'h']
[1, 'i', 'j']
[2, 'k', 'l']

def defineSection(i, division, height):
    if i <= division:
        return 1
    elif division*2 >= i > division :
        return 2
    elif division*3 >= i > division*2 :
        return 3

dic = {}
for i in range(height):
    for j in range(1,width):
        section = defineSection(i+1, 2, height)
        dic.update({array2d[i][j] : section})

for item in dic.items():
    print(item)

('f', 2)
('b', 1)
('c', 1)
('e', 2)
('k', 3)
('g', 2)
('d', 1)
('a', 1)
('l', 3)
('h', 2)
('i', 3)
('j', 3)

In [3]: from itertools import cycle

In [4]: letters = "abcdefghijkl"

In [5]: iter_letters = iter(letters)

In [6]: matrix = [[i,a,b] for i,a,b in zip(ranges,iter_letters,iter_letters)]

In [7]: matrix
Out[7]:
[[2, 'a', 'b'],
 [1, 'c', 'd'],
 [2, 'e', 'f'],
 [1, 'g', 'h'],
 [2, 'i', 'j'],
 [1, 'k', 'l']]

In [8]: sections = {letter:(i//2 + 1) for i,letter in enumerate(letters)}

In [9]: sections
Out[9]:
{'a': 1,
 'b': 1,
 'c': 2,
 'd': 2,
 'e': 3,
 'f': 3,
 'g': 4,
 'h': 4,
 'i': 5,
 'j': 5,
 'k': 6,
 'l': 6}