title: How do I change the element of a list with user input?
body: <p>I'm trying to change an element of a list by doing this:</p>
  
  <pre><code>board = []
  for i in range(3):
      board.append("-"*3)
  
  def print_board(board):
      for row in board:
          print " ".join(row)
  
  print_board(board)
  print "Welcome to tic tac toe. You go first because I say so."
  column = int(raw_input("Enter column number: "))
  row = int(raw_input("Enter row number: "))
  
  board[row][column] = "O" #THIS ONE
  print_board(board)
  </code></pre>
  
  <p>but the error message "TypeError: 'str' object does not support item assignment" shows up. What should I do?</p>