a = [9, 1, 9, 74888, 29, 2, 29, 55586, 29, 2, 29, 19827,
     23, 2, 23, 62839, 50, 3, 50, 56642]

a = [[9, 1, 9, 74888],
     [29, 2, 29, 55586],
     [29, 2, 29, 19827],
     [23, 2, 23, 62839],
     [50, 3, 50, 56642]]

In [24]: N=4

In [25]: res = [a[i*N:i*N+N] for i in range(len(a)//N)]

In [26]: res
Out[26]:
[[9, 1, 9, 74888],
 [29, 2, 29, 55586],
 [29, 2, 29, 19827],
 [23, 2, 23, 62839],
 [50, 3, 50, 56642]]