Tic-Tac-Toe Implementation in Python

Tic-Tac-Toe

#
# CONSTANTS
#

PLAYER_ICON = 'X'
BOARD_SIZE = 3
WELCOME_MESSAGE = ''
WIN_MESSAGE = ''
INVALID_MOVE_MESSAGE = ''
BOARD_PRINT_FORMAT = '''
{0}|{1}|{2}
-----
{3}|{4}|{5}
-----
{6}|{7}|{8}
'''

board = [[' '] * BOARD_SIZE] * BOARD_SIZE

#
# Check if a move is valid on a certain board
# Returns True or False
#

def check_valid_move(board, move):
	return True

#
# Play a move and return the board, move must be valid
# Returns board
#

def play_move(board, player, move):
	return board

#
# Given a board, check if player has won
# Values for player = 'X' or 'O'
# Returns True or False
#

def check_win(board, player):
	return False

#
# Checks if the board is full
# Returns True if the board is full or False otherwise
#

def check_board_full(board):
	return True

#
# Returns a random empty position in the board
#

def generate_random_move(board):
	return

#
# Returns the icon opposite to player_icon
#

def choose_ai_icon(player_icon):
  if player_icon == 'X':
    return 'O'
  if player_icon == 'O':
    return 'X'

def format_board(board, print_format):
	return print_format.format(board[0][0], board[0][1], board[0][2],
				   board[1][0], board[1][1], board[1][2],
				   board[2][0], board[2][1], board[2][2])

#
# Main
#

def main():
	print(WELCOME_MESSAGE)
	print format_board(board,BOARD_PRINT_FORMAT)
	AI_ICON = choose_ai_icon(PLAYER_ICON)
	return

if __name__ == '__main__':
	main()

Incomplete command-line tic-tac-toe in Python.