ls = [1, 2, 3, 4, 5, 6, 7, 8, 9]

ls = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

>>> nls=[]
>>> for i in range(0,3):nls.append(ls[3*i:3*i+3])
>>> nls
[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

In [132]: ls = [1, 2, 3, 4, 5, 6, 7, 8, 9]

In [133]: [ls[i*3:i*3+3] for i in range((len(ls)//3 + (len(ls)%3>0)*1))]
Out[133]: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

In [134]: ls = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

In [135]: [ls[i*3:i*3+3] for i in range((len(ls)//3 + (len(ls)%3>0)*1))]
Out[135]: [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]

In [136]: ls = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

In [137]: [ls[i*3:i*3+3] for i in range((len(ls)//3 + (len(ls)%3>0)*1))]
Out[137]: [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11]]

In [138]: ls = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

In [139]: [ls[i*3:i*3+3] for i in range((len(ls)//3 + (len(ls)%3>0)*1))]
Out[139]: [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]]

result = [ls[i:i+3] for i in range(0, len(ls), 3)]