Tic Tac Toe

tictactoe.py

#!/usr/bin/python
from __future__ import print_function
"""
tictactoe.py
"""

import sys


def DrawBoard(board, f=sys.stdout):
  """Draw a tic-tac-toe board as ASCII art."""

  for x in range(3):
    f.write('%d|' % x)
    for y in range(3):
      char = board[x, y]
      f.write(char)
      f.write('|')
    f.write('\n')

  print('  A B C')  # to show the row


# Translate from user input to an integer index.
Y_COORD = {'A': 0, 'B': 1, 'C': 2}


def GetMove(board, name):
  """Prompt for and validate a 2-character move like '0A'."""

  while True:
    move = raw_input('Player %s, enter a move (XY, e.g. 0A or 2C): ' % name)
    move = move.strip()
    if len(move) != 2:
      print('Invalid move %r' % move)
      continue

    x_str = move[0]
    y_str = move[1].upper()
    if x_str not in '012' or y_str not in 'ABC':
      print('Invalid move %r' % move)
      continue

    x = int(x_str)
    y = Y_COORD[y_str]
    if board[x, y] != ' ':
      print("Position %r isn't empty" % move)
      continue

    return x, y


def CheckForWin(board, name):
  """Returns a string that describes the win, or None if no win."""

  for x in range(3):
    if all(board[x, y] == name for y in range(3)):
      return 'Player %s won in row %d!' % (name, x)

  for y in range(3):
    if all(board[x, y] == name for x in range(3)):
      return 'Player %s won in column %d!' % (name, y)

  if all(board[i, i] == name for i in range(3)):
    return 'Player %s won on the left diagonal!' % name

  if (board[0, 2] == name and
      board[1, 1] == name and
      board[2, 0] == name):
    return 'Player %s won on the right diagonal!' % name

  return None


def NewBoard():
  """Initialize the board."""

  board = {}
  for x in range(3):
    for y in range(3):
      board[x, y] = ' '  # empty
  return board


def main(argv):
  # Test()
  # return

  board = NewBoard()

  while True:
    # Player X
    DrawBoard(board)
    x, y = GetMove(board, 'x')
    board[x, y] = 'x'

    msg = CheckForWin(board, 'x')
    if msg:
      DrawBoard(board)
      print(msg)
      break

    # Player O
    DrawBoard(board)
    x, y = GetMove(board, 'o')
    board[x, y] = 'o'

    msg = CheckForWin(board, 'o')
    if msg:
      DrawBoard(board)
      print(msg)
      break

  print('GAME OVER')


def Test():
  board = NewBoard()

  board[0, 0] = 'x'
  board[0, 1] = 'x'
  assert not CheckForWin(board, 'o')
  assert not CheckForWin(board, 'x')
  board[0, 2] = 'x'
  DrawBoard(board)
  assert CheckForWin(board, 'x')

  board = NewBoard()

  board[0, 1] = 'o'
  board[1, 1] = 'o'
  assert not CheckForWin(board, 'o')
  assert not CheckForWin(board, 'x')
  board[2, 1] = 'o'
  DrawBoard(board)
  assert CheckForWin(board, 'o')

  board = NewBoard()

  board[0, 0] = 'o'
  board[1, 1] = 'o'
  assert not CheckForWin(board, 'o')
  assert not CheckForWin(board, 'x')
  board[2, 2] = 'o'
  DrawBoard(board)
  assert CheckForWin(board, 'o')

  board = NewBoard()

  board[2, 0] = 'o'
  board[1, 1] = 'o'
  assert not CheckForWin(board, 'o')
  assert not CheckForWin(board, 'x')
  board[0, 2] = 'o'
  DrawBoard(board)
  assert CheckForWin(board, 'o')


if __name__ == '__main__':
  main(sys.argv)