Create a 2D list out of 1D list

Question

I am a bit new to Python and I want to convert a 1D list to a 2D list, given the width and length of this matrix.

Say I have a list=[0,1,2,3] and I want to make a 2 by 2 matrix of this list.

How can I get matrix [[0,1],[2,3]] width=2, length=2 out of the list?

Asked By: PhoonOne

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Source

Answer 1

Try something like that:

In [53]: l = [0,1,2,3]

In [54]: def to_matrix(l, n):
    ...:     return [l[i:i+n] for i in xrange(0, len(l), n)]

In [55]: to_matrix(l,2)
Out[55]: [[0, 1], [2, 3]]

Answered By: root

Answer 2

I think you should use numpy, which is purpose-built for working with matrices/arrays, rather than a list of lists. That would look like this:

>>> import numpy as np
>>> list_ = [0,1,2,3]
>>> a = np.array(list_).reshape(2,2)
>>> a
array([[0, 1],
       [2, 3]])
>>> a.shape
(2, 2)

Avoid calling a variable list as it shadows the built-in name.

Answered By: wim

Answer 3

not as elegant and pretty specific to yours, but you create 2 lists (every other integer) and zip/list them back together.

full_list = [0, 1, 2, 3]
list1 = []
list2 = []
for i in full_list:
  if i % 2 == 0:
    list1.append(i)
  else:
    list2.append(i)

zip_list = zip(list1, list2)
done = list(zip_list)

output:
[(0, 1), (2, 3)]

Answered By: CrypticCoder

Create a 2D list out of 1D list

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