How do I create a list of lists where I can index each list individually?

May 23, 2023

I’m trying to create a list that contains 10 lists each with ten empty "space" strings making a ten by ten matrix. The problem is that when I index to add a number to the first position, it adds a 1 to the beginning of each list in the outer list. How do I make it so when I index it only adds a 1 to the first position of the entire matrix (the first spot of the first list in the outer list)?

unit = ' '
lst = []
for y in range(10):
  lst.append(unit)
board = []
for x in range(10):
  board.append(lst)
board[0][0] = 1
print(*board, sep = '\n')

This code makes is so a 1 appears at the beginning of each list in the outer list. But I want only a 1 at the beginning of the first list.

>Solution :

You could just use list on a string which makes a list of each character in the string.

unit = " " * 10
board = [list(unit) for _ in range(10)]
board[0][0] = 1

Result

[
    [1, ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
    [' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '],
]