问Tac Tac Toe嵌套列表问题

EN

board = [['-','-','-']
        ,['-','-','-']
        ,['-','-','-']]
player1 = 'X'
player2 = 'O'
win = False
turns = 0
player1= str(input("Whats ur name+"))
player2= str(input("Whats ur name"))
def checkwin(player):

  for c in range(0,3):

    if board[c][0] == player and board[c][1] == player and board[c][2] == player:
      print "*********\n\n%s wins\n\n*********" % player
      playerwin = True
      return playerwin

    elif board[0][c] == player and board[1][c] == player and board[2][c] == player:
      print "*********\n\n%s wins\n\n*********" % player
      playerwin = True
      return playerwin
    #check for diagonal win
    elif board[0][0] == player and board[1][1] == player and board[2][2] == player:
      print "*********\n\n%s wins\n\n*********" % player
      playerwin = True
      return playerwin
    #check for diagonal win (right to left)
    elif board[0][2] == player and board[1][1] == player and board[2][0] == player:
      print "*********\n\n%s wins\n\n*********" % player
      playerwin = True
      return playerwin
  else:
    playerwin = False
    return playerwin


def playerturn(player):
  print "%s's turn" % player
  turn = 1
  while(turn):
    print "Select column [1-3]: ",
    col = int(raw_input()) - 1
    print "Select row [1-3]: ",
    row = int(raw_input()) - 1
    if board[row][col] == "X" or board[row][col] == "O":
      print "Already taken!"
    else:
      board[row][col] = player
      turn = 0

def printboard():
  print board[0]
  print board[1]
  print board[2]


printboard()
while(win == False):
  playerturn(player1)
  turns += 1
  printboard()
  if checkwin(player1) == True: break
  if turns == 9:
    print "This game is a draw!"
    break

  playerturn(player2)
  turns += 1
  printboard()
  checkwin(player2)
  if checkwin(player2) == True: break