Create a two-dimensional (2D) array using lists in Python

Question

I want to create a 2D array using lists. Each list should be a column in the matrix. How can I do that?

I tried numpy's hstack() and append(), but it did not work.

E.g.:

a = [1, 2, 3]

b = [4, 5, 6]

output:

[[1, 4],

 [2, 5],

 [3, 6]]

Answer 1

Since you want lists to be columns of the matrix, you need to first reshape the lists and then you can use hstack().

Here is an example:

>>> a
[1, 2, 3]
>>> b
[4, 5, 6]
>>> c
[7, 8, 9]
>>> np.hstack((np.reshape(a, (len(a),1)), np.reshape(b, (len(b),1)), np.reshape(c, (len(c),1))))
array([[1, 4, 7],
       [2, 5, 8],
       [3, 6, 9]])