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

Answer 1

NumPy's built-in reshape function can be used to do such a task.

import numpy

length = 2
width = 2
_list = [0,1,2,3]
a = numpy.reshape(a, (length, width))
numpy.shape(a)

As long as you change the values within your list, and accordingly update the values of 'length' and 'width', you shouldn't receive any error.

Answer 2

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]]

Answer 3

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.