IndexError: list index out of range stone_wall, 21

Hi, I decided to grab all the cols where there are 2 zeros and than choose col with smallest index as left most column But i get error: "IndexError: list index out of range" . To me it is not clear. please advice:

def stone_wall(wall):


matrix = [list(x) for x in wall.splitlines()]
matrix = [col for col in matrix if len(col) != 0]

indexes=[]
weakest_places=[]
if '0' in wall:
    for x in range(len(matrix)):
        for y in range(len(matrix[x])):
            if matrix[x][y] == '0':
                indexes.append(y)


    weakest_places = [x for x in indexes if indexes.count(x) ==2]

    # remove duplicates
    w_places=set(weakest_places)
    weakest_places=list(w_places)
    weakest_places.sort()

    return weakest_places[0]
else:
    return 0