An automatic maze solver thing I wrote in python while in CS160 class

maze.py

# enter in the maze content in ascii here
maze = [list('######################'),
        list('#S #### #     #     ##'),
        list('## #### # ##### ### ##'),
        list('##      #       ###E##'),
        list('####### ####### ######'),
        list('##    #     ###     ##'),
        list('## ########   ##### ##'),
        list('##    ####### ##### ##'),
        list('## ##               ##'),
        list('######################')
        ]

# define characters to control maze
wall = '#'
start = 'S'
end = 'E'

# these will be automatically calculated, leave them alone
position_start = [0, 0]
position_end = [0, 0]
alreadytested = list()

# find start position
for y in range(0, len(maze)):
    for x in range(0, len(maze[y])):
        if maze[y][x] == start:
            position_start = [x, y]
            break

# walk a position in the maze
def walk(pos):    
    x = pos[0]
    y = pos[1]

    # make record that x,y was tested, and make new combinations to test
    alreadytested.append([x, y])
    totest = [[x - 1, y], [x + 1, y], [x, y - 1], [x, y + 1]]

    # basic checks
    if maze[y][x] == end:
        global position_end
        position_end = [x, y]
        return True
    elif maze[y][x] == wall:
        return False
    else:
        maze[y][x] = 'X'

    # loop through each combination of walking in xy direction
    for test in totest:
        x = test[0]
        y = test[1]
        
        # check if the x and y values are in range and if so, try walking them
        if y >= 0 and y < len(maze) and x >= 0 and x < len(maze[y]) and maze[y][x] != wall and not [x, y] in alreadytested:
            if walk([x, y]):
                maze[y][x] = '.'
                return True
    return False

# solve maze
solvable = walk(position_start)
maze[position_start[1]][position_start[0]] = start
if solvable:
    print('Maze solved!')
    maze[position_end[1]][position_end[0]] = end
else:
    print('Maze not solved!')

# print out maze solution
for row in maze:
    content = ''
    for c in row:
        content += c
    print(content)