1 directions = [(-1, -1), (-1, 0), (-1, 1),
   2               (0, -1),           (0, 1),
   3               (1, -1 ), (1, 0), (1, 1)]
   4 
   5 switch = { 'b': 'w', 'w': 'b'}
   6 
   7 
   8 def legal_moves(board, player):
   9     stones = find_pieces(board, player)
  10     moves = []
  11     for stone in stones:
  12         moves += (find_valid_paths(board, stone))
  13     return set(moves)
  14 
  15 
  16 def find_pieces(board, colour):
  17     l = []
  18     for (i, col) in enumerate(board):
  19         for (j, row) in enumerate(col):
  20             if row == colour:
  21                 l.append((i,j))
  22     return set(l)
  23 
  24 
  25 def check_direction(board, start, direction):
  26     (row, col) = start
  27     me = board[row][col]
  28 
  29     if me == ".":
  30         return
  31 
  32     other = switch[me]
  33     between = False
  34 
  35     while True: 
  36         row += direction[0]
  37         col += direction[1]
  38 
  39         if row < 0 or col < 0 or row > len(board)-1 or col > len(board[0])-1:
  40             break
  41 
  42         checked = board[row][col]
  43 
  44         if  checked == other:
  45             between = True
  46             continue
  47         elif checked == "." and between:
  48             return (row, col)
  49         else:
  50             return
  51 
  52 
  53 def find_valid_paths(board, position):
  54     coords = []
  55     for direction in directions:
  56         result = check_direction(board, position, direction)
  57         if result:
  58             coords.append(result)
  59     return set(coords)