Python 2d lists

A list of lists is a grid: grid[row][col]. Read one row per line, each turned into numbers.

Loop over rows, then over the columns inside each row. zip(*grid) turns rows into columns.

grid = [[1, 2, 3], [4, 5, 6]]
for row in grid:
    print(*row)
print(grid[1][2])  # 6

Watch for: [[0] * 3] * 2 makes two names for the same row: changing one changes both. Build rows with a comprehension: [[0] * 3 for _ in range(2)].