How to create list [x][y] with string data of unknown size?

Question

Python

arr[0][0] = '1'
arr[0][1] = '2'
arr[1][0] = '3'
arr[1][1] = '4'

print(arr)

[['1','2'],['3','4']]

Tried but gives an error
arr = [[0] * len_y for i in range(len_x)]

Answer 1

Not quite clear. Do you want a two dimensional array? You get it. What's wrong?