How to convert a list into a matrix without numpy?

Question

I have a list like this: A_list = [0, 5, 20, 0, 1, 8, 0, 14, 7, 5, 11, 0, 7, 0, 4, 0, 0, 0].

I want it to convert into 'matrix' form in python without using numpy.

A_matrix = [ [0, 0, 0, 5, 7, 0],
             [5, 1, 14, 11, 0, 0],
             [20, 8, 7, 0, 4, 0]
           ]

Please see [here](https://stackoverflow.com/questions/5850536/how-to-chunk-a-list-in-python-3). — thornejosh, Mar 31 '21 at 17:34

score 1 · Accepted Answer · answered Mar 31 '21 at 17:34

You can use a list comprehension to stride through the array, where each inner list starts at a different offset

>>> [A_list[start::3] for start in range(3)]
[[0, 0, 0, 5, 7, 0], [5, 1, 14, 11, 0, 0], [20, 8, 7, 0, 4, 0]]

This is basically what you'd achieve with numpy.reshape

>>> np.array(A_list).reshape((-1,3)).T
array([[ 0,  0,  0,  5,  7,  0],
       [ 5,  1, 14, 11,  0,  0],
       [20,  8,  7,  0,  4,  0]])

1 Answers1