Tic-Tac-Toe Game in Python

In this article we’ll see how to develop tic-tac-toe game in Python.

The tic-tac-toe game we are going to develop is a two player game played in the command line. Steps in the program are as follows-

Give an option to the player 1 to choose symbol (‘X’ or ‘O’).
Create a tic-tac-toe board with index numbers making it easy for the players to input the index where they want their symbol to be placed.
Give each player a chance to place the symbol alternatively until one of the players has won the game or the game is drawn.

Tic-tac-toe game – Python code

def user_choice():
  choice = ' '
  flag = False
  while not choice.isdigit() or not flag:
    choice = input('Please input a number (0-10): ')
    if choice.isdigit() and int(choice) in range(0, 10):
      flag = True
      return int(choice)
    else:
      print('Enter number between 0 and 10')
      flag = False


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


def player_input():
  marker = ''
  while not (marker == 'X' or marker == 'O'):
      marker = input('Player 1: Do you want to be X or O? ').upper()
  if marker == 'X':
      return ('X', 'O')
  else:
      return ('O', 'X')


def place_symbol(board, symbol, position):
  if board[position] in ('X', 'O'):
    print('Position already marked')
  board[position] = symbol


def check_marked_position(board, position):
  if board[position] in ('X', 'O'):
    print('Position already marked')
    return False
  return True


def select_player_position(board, player):
  position = 0
  while position not in range(1, 10) or not check_marked_position(board, position):
    position = int(input(player + ' Choose your next position: (1-9) '))
  return position


def is_winner(board, symbol):
  return ((board[1] == symbol and board[2] == symbol and board[3] == symbol) or  # top row
          (board[4] == symbol and board[5] == symbol and board[6] == symbol) or  # middle row
          (board[7] == symbol and board[8] == symbol and board[9] == symbol) or  # bottom row
          (board[1] == symbol and board[4] == symbol and board[7] == symbol) or  # first column
          (board[2] == symbol and board[5] == symbol and board[8] == symbol) or  # second column
          (board[3] == symbol and board[6] == symbol and board[9] == symbol) or  # third column
          (board[1] == symbol and board[5] == symbol and board[9] == symbol) or  # diagonal
          (board[3] == symbol and board[5] == symbol and board[7] == symbol))  # diagonal


def is_board_full(board):
  full_flag = True
  for i in range(1, 10):
    if board[i] not in ('X', 'O'):
      full_flag = False
  return full_flag


def start_play():
  while True:
    player1_symbol, player2_symbol = player_input()
    tictac_board = ['#', '1', '2', '3', '4', '5', '6', '7', '8', '9']
    turn = 'Player1'
    play_again_flag = 'Y'
    symbol = ''
    display_board(tictac_board)
    while True:
      if turn == 'Player1':
        symbol = player1_symbol
      else:
        symbol = player2_symbol

      position = select_player_position(tictac_board, turn)
      place_symbol(tictac_board, symbol, position)
      display_board(tictac_board)
      if is_winner(tictac_board, symbol):
        print('Yeey! ' + turn + ' won!')
        break
      if is_board_full(tictac_board):
        print('It''s a draw!')
        break
      else:
        turn = 'Player2' if turn is 'Player1' else 'Player1'


      play_again_flag = input('Do you want to play again? Enter Y or N: ')
      print(play_again_flag.lower())
      if play_again_flag.lower() != 'y':
        break

start_play()

start_play() function is the main function where first task is to ask player 1 to choose preferred symbol out of ‘X’ or ‘O’. This is done by calling player_input() function.
To display tic-tac-toe board display_board() function is called passing list tictac_board = ['#', '1', '2', '3', '4', '5', '6', '7', '8', '9'] as an argument. Since index 0 is not required so that has a placeholder value ‘#’.
In a while loop each player gets a chance to place their respective symbol. Functions used for this task are select_player_position() and place_symbol().
While placing a symbol it is required to check if the selected position is already marked or not that is done using check_marked_position() function.
After each turn it is also required to check if there is a winner that is done using is_winner() function. Another thing to check is whether the board is full that is done using is_board_full() function.

That's all for the topic Tic-Tac-Toe Game in Python. If something is missing or you have something to share about the topic please write a comment.

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