Tic Tac Toe 2-player

# This constant contains all the space keys for a tic tac toe board:
ALL_SPACES = ['1', '2', '3', '4', '5', '6', '7', '8', '9']

def printBoard(board):
    print('      ' + board['1'] + '|' + board['2'] + '|' + board['3'] + '  1 2 3')
    print('      -+-+-')
    print('      ' + board['4'] + '|' + board['5'] + '|' + board['6'] + '  4 5 6')
    print('      -+-+-')
    print('      ' + board['7'] + '|' + board['8'] + '|' + board['9'] + '  7 8 9')


def getNewBoard():
    return {'1': ' ', '2': ' ', '3': ' ', '4': ' ',
            '5': ' ', '6': ' ', '7': ' ', '8': ' ', '9': ' '}


def getPlayerMove(board, mark):
    while True:
        print('What is ' + mark + "'s move? (1-9)")
        move = input()
        if move in ALL_SPACES:
            if board[move] == ' ':
                return move


def boardIsFull(board):
    for space in ALL_SPACES:
        if board[space] == ' ':
            return False
    return True


def isWinner(board, mark):
    # Check the horizontal rows:
    if board['1'] == board['2'] == board['3'] == mark:
        return True
    if board['4'] == board['5'] == board['6'] == mark:
        return True
    if board['7'] == board['8'] == board['9'] == mark:
        return True
    # Check the vertical columns:
    if board['1'] == board['4'] == board['7'] == mark:
        return True
    if board['2'] == board['5'] == board['8'] == mark:
        return True
    if board['3'] == board['6'] == board['9'] == mark:
        return True
    # Check the diagonals:
    if board['1'] == board['5'] == board['9'] == mark:
        return True
    if board['3'] == board['5'] == board['7'] == mark:
        return True
    return False



print('Welcome to Tic Tac Toe!')
theBoard = getNewBoard()
turn = 'X'

printBoard(theBoard)

# Main game loop that asks for a player's move:
while True:
    # Get the player's move:
    playerMove = getPlayerMove(theBoard, turn)

    # Update the dictionary that represents the board with this move:
    theBoard[playerMove] = turn

    # Display the updated board on the screen:
    printBoard(theBoard)

    # Detect if the player has three in a row and won:
    if isWinner(theBoard, turn):
        print(turn + ' is the winner!')
        break

    # Detect if the board is full, and the game is a tie:
    if boardIsFull(theBoard):
        print('The game is a tie!')
        break

    # Change whose turn it is.
    if turn == 'X':
        turn = 'O'
    else:
        turn = 'X'

# End of program:
print('Thanks for playing!')