2-player Tic-Tac-Toe

tictactoe.py

#!/usr/bin/env/python

grid = [' '] * 9
curTurn = 'O'

#Print the X and O grid representing current game state
def displayBoard(board):
    print "%s | %s | %s" % (board[0], board[1], board[2])
    print "---------"
    print "%s | %s | %s" % (board[3], board[4], board[5])
    print "---------"
    print "%s | %s | %s" % (board[6], board[7], board[8])

#Check if someone won through the last move
def isWin(board):
    return ((board[0] == board[1] and board[1] == board[2] and board[0] != ' ') or # top row
            (board[3] == board[4] and board[4] == board[5] and board[3] != ' ') or # middle row
            (board[6] == board[7] and board[7] == board[8] and board[6] != ' ') or # bottom row
            (board[0] == board[3] and board[3] == board[6] and board[0] != ' ') or # left column
            (board[1] == board[4] and board[4] == board[7] and board[1] != ' ') or # middle column
            (board[2] == board[5] and board[5] == board[8] and board[2] != ' ') or # right column
            (board[0] == board[4] and board[4] == board[8] and board[0] != ' ') or # negative diagonal
            (board[2] == board[4] and board[4] == board[6] and board[2] != ' '))   # positive diagonal

#Check if there are no longer any game moves to make and nobody has already won
#Game is declared a tie as a result then
def isTie(board):
    if ' ' not in board:
        return True
    return False

#Turn changes hand
def flipTurn(curTurn):
    if curTurn == 'X':
        return 'O'
    elif curTurn == 'O':
        return 'X'

#Map a 2D given location to the 1D array storing Xs and Os
def computeLocation(row, col):
    return (row * 3) + col

#
#Actual main part of the program
#

while not isWin(grid) and not isTie(grid):
    displayBoard(grid)
    curTurn = flipTurn(curTurn)
    #Prompt for user's choice of spot
    row = input("Please input row number: ")
    col = input("Please input column number: ")
    
    #Check if invalid grid table location is given
    if row not in range(3) or col not in range(3):
        print "INVALID spot: Appropriate range is 0-2"
        #Counter-acts the change turn done at the beginning of the loop
        curTurn = flipTurn(curTurn)
        continue

    spot = computeLocation(row, col)

    #Check if location is illegal. If so, must re-input
    if grid[spot] != ' ':
        print "INVALID spot: Already filled. Please replay"
        #Counter-acts the change turn done at the beginning of the loop
        curTurn = flipTurn(curTurn)
        continue

    #Place user's move in appropriate spot
    grid[spot] = curTurn

#Game is over by some means if it goes past this point

if isWin(grid):
    displayBoard(grid)
    print "%s wins the game!" % curTurn

if isTie(grid):
    displayBoard(grid)
    print "Nobody wins the game."