Python错误：列表索引超出范围

我用python编写了一个战舰游戏。这是代码：

#!/usr/bin/python

"""Battleship: Command Line Python Game

This is a classical version of the battleship game.

There is a board in which a battleship is randomly placed in a spot. User who correctly guesses the spot wins the game.

User have eight turns to guess correct cordinates

The game is coded in python 2"""

#imports randint from random to generate random numbers
from random import randint

#creating the board
board = []

#Filling up the board
for x in range(5):
  board.append(["O"] * 6)

#Function to print out the board to user
def print_board(board):
  for row in board:
    print " ".join(row)

#Call to print board to user
print_board(board)

#Function to generate random battleship row
def random_row(board):
  return randint(0, len(board) - 1)

#Function to generate random battleship coloumn
def random_col(board):
  return randint(0, len(board[0]) - 1)

#Call to generate random row and coloumn
ship_row = random_row(board)
ship_col = random_col(board)

#Snippet for debugging
print ship_row
print ship_col
#Snippet for debugging

#Running Turns
for turn in range(8):

  #Print out turn number to user
  print "Turn: " + str(turn + 1)

  #Accepts users guess
  guess_row = int(raw_input("Guess Row: "))
  guess_col = int(raw_input("Guess Col: "))

  #Check if correct guess
  if guess_row == ship_row and guess_col == ship_col:
    #Congratulate the guess
    print "Congratulations! You sunk my battleship!"
    #Exit loop and Game Over
    print "Game Over"
    break

  #If not correct guess
  else:

    #Check weather input is valid
    if (guess_row < 0 or guess_row > 5) or (guess_col < 0 or guess_col > 5):
      #Inform an invalid input
      print "Oops, that's not even in the ocean."

    #Check weather repeated guess
    elif(board[guess_row][guess_col] == 'X'):
      #Inform a repeated guess
      print "You guessed that one already."

    #For valid new input
    else:
      #Inform a missed shot
      print "You missed my battleship!"
      #Fill guessed place with X and print out the board
      board[guess_row][guess_col] = 'X'
      print_board(board)

    #Check Weather out of Turns
    if turn == 7:
      #GAME OVER
      print "Game Over"

似乎显示错误：这是终端错误的完整描述：

追溯（最近一次通话最近）：文件“ /home/prem59/Dropbox/Python/Codecademy/battleship.py”，第77行，位于if（board [guess_row] [guess_col] =='X'）：IndexError：列表索引超出范围

我认为elif语句正在引起麻烦。但是，如果删除它，将无法检查用户是否输入了重复输入。如何解决此问题而不影响程序的功能？