a = [[1,2,3,4,5],[1,4,6,8,9],[6,5,3,2,1]]
b = tuple(a)
print (b)
c = a[:]
stroka = -1
stolbets = -1
for i in a: 
    stroka += 1
    for p in i:
        stolbets += 1
        if stolbets == len(a[1]):
            stolbets = 0
        try:
            c[stroka][stolbets]= b[stroka][stolbets+1]+b[stroka][stolbets-1]
        except:
            c[stroka][stolbets]= b[stroka][0]+b[stroka][stolbets-1]
print(c)
#b[1]= 7 
print(b)

a = [[1,2,3,4,5],[1,4,6,8,9],[6,5,3,2,1]]
b = [tuple(x) for x in a]
print(b)

>>> a = [[1, 2, 3, 4, 5], [1, 4, 6, 8, 9], [6, 5, 3, 2, 1]]
>>> b = tuple(map(tuple, a))
>>> b
((1, 2, 3, 4, 5), (1, 4, 6, 8, 9), (6, 5, 3, 2, 1))
>>>