game.py

#so that I can PR
def print_board(board):
	print ' '.join(['-' if i == None else str(i) for i in board][:3])
	print ' '.join(['-' if i == None else str(i) for i in board][3:6])
	print ' '.join(['-' if i == None else str(i) for i in board][6:])

def play():
	while None in board:
		print_board(range(9))
		print ''
		print_board(board)

		board[int(raw_input('Which space? '))] = 1 # I go first always, instead of computer
		print_board(board)

		if check_win(board)[0]:
			print_win(board)
			break

		print '\nNow, computer goes...\n'

		move = move_helper(board, 0)
		#print move
		board[move[1]] = 0
		print_board(board)
		print '\n'

		if check_win(board)[0]:
			print_win(board)
			break

def print_win(board):
	result = check_win(board)[1]
	if result == 1:
		print 'Player wins'
	elif result == 0:
		print 'Tie'
	elif result == -1:
		print 'Computer wins'

def check_win(board):
	winning_positions = [
		[0,1,2],
		[3,4,5],
		[6,7,8],
		[0,4,8],
		[2,4,6],
		[0,3,6],
		[1,4,7],
		[2,5,8]]

	for position in winning_positions:
		if False not in [board[i] == 1 for i in position]: # all positions are 1
			return [True , 1]
		elif False not in [board[i] == 0 for i in position]: # all positions are 0; I lose
			return [True, -1]
		elif None not in board: # a tie
			return [True, 0]

	return [False] # not a tie; no one has one

def move_helper(board, side):
	board = board[:] # copies the list board
	best = [None, None]

	result = check_win(board)
	if result[0]: # i don't need side == 0 bc 0 can only win on 0s turn. right?
		return [result[1]] # before I had 0 instead of None. But I don't state a position to move, right?

	if side == 0:
		best[0] = 1 # was -1 before
	else:
		best[0] = -1

	avail_moves = [i for i in range(len(board)) if board[i] == None]

	for i in range(len(avail_moves)): # bc i found that i can't pop() sth if it's being held by for loop
		temp_pop = avail_moves.pop()
		board_copy = board[:]
		board_copy[temp_pop] = side # was i before
		reply = move_helper(board_copy, abs(side - 1))
		avail_moves.insert(0, temp_pop) # push to the beginning? depends on pop(i) beh

		if (side == 0 and reply[0] <= best[0]) or (side == 1 and reply[0] >= best[0]):
			best[0] = reply[0]
			#print 'best result is {} when board looks like this:'.format(best)
			#print_board(board_copy)
			best[1] = temp_pop

	return best

def test():
	board = [0,1,0,None,1,None,1,None,None]
	print_board(board)

	print move_helper(board, 0)


board = [None for i in range(9)]
#test()
#board = [0,1,0,None,1,None,1,None,None]
play()