Why am I getting a list index out of range error when traversing a list matrix?

Question

I am trying to iterate through a matrix list i.e (go 3 values to the right, 1 down) and seeing the above error. The expected value is being printed to the console, which would suggest the value exists and is not out of range.

grid = []

with open(filename) as f:
    for line in f.readlines():
        line.strip()
        grid.append(line)
print(grid)

col = 2
row = 0
count = 0

for i in enumerate(grid):
    row = row + 1
    print(grid[row][col])
    if grid[row][col] == "#":
        print("found")
        print(grid[row][col])
        count = count+1
    col = col + 3

This problem also persists if I don't increment the row and col values. My input data is here:

.........###......#...#.......#
.#.#...........#..#..#.........
#.......#.................#....
.........#.#.........#......###
.....#......##...##............
...##...#......#.....#.....##..
#.#..#....#...#....#......#....
........##.....#.....#.#.......
......#.....#......#...##.#....
...####...#.......##.....#.#...
.........#....#......##........
..##...........###.#...........
.....#............#............
#.#..#..##........#.....#..#...
.....................#....##..#
...........##.....###...#.#.#..
..#......#...........#.........
.##.##...#...#......##.#.......
......#..#......#.#.#..#.#.....
........#.#..#..........#...#.#
...........##...........#....#.
...........#...##.#............
.......#...........#...........
.......#......#..#...#....#..#.
..#.....#.#....#.#......#...#.#
.#..........###..#....#........
........##..#..#...#..#....#..#
#..........#...#..#.#........#.
..#.#........##.##....##.#.....
#.##....#...#.......#.#..#....#
......##...#.#.#.#.....#....#..
..........#..............#.....
....................###.#......
#.....#...#...#.#.......#....#.
.......#..#...................#
........##.##........#......#..
...#...##.#...#...........#....
..#.........#...#....##......#.
......#..............#..#..#.#.
.....##...#...#...##....#......
#.#....#...#......##.....#...##
.#...#.#..................#....
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Answer 1

Python lists(and matrices) are zero indexed.

You are adding 1 to the row too early, so in the last row you instead try to access the nonexistent row after the last one. Try placing the row = row + 1 just before the col = col + 1. Then proceed to debug from there.

Alternatively you could start with row = -1, which should work however it is kind of 'dirty'.

Also since you are already using enumerate, you might want to consider

for idx, i in enumerate(grid):
    grid[idx][col] == '#'

since enumerate already gives you the indices you need.