Tic Tac Toe - Invent Your Own Computer Games with Python - page 181

10 - Tic Tac Toe
We want to check if the computer won with its last move. The reason we call
drawBoard() here is because the player will want to see what move the computer made
to win the game. We then set gameIsPlaying to False so that the game does not
continue. Notice that lines 174 to 177 are almost identical to lines 157 to 160.
178. else:
179. if isBoardFull(theBoard):
180. drawBoard(theBoard)
181. print('The game is a tie!')
182. break
These lines of code are identical to the code on lines 162 to 165. The only difference is
this is a check for a tied game after the computer has moved.
183. else:
184. turn = 'player'
If the game is neither won nor tied, it then becomes the player's turn. There are no more
lines of code inside the while loop, so execution would jump back to the while
statement on line 150.
186. if not playAgain():
187. break
These lines of code are located immediately after the while-block started by the while
statement on line 150. Remember, we would only exit out of that while loop if it's
condition (the gameIsPlaying variable) was False . gameIsPlaying is set to
False when the game has ended, so at this point we are going to ask the player if they
want to play again.
Remember, when we evaluate the condition in this if statement, we call the
playAgain() function which will let the user type in if they want to play or not.
playAgain() will return True if the player typed something that began with a 'y' like
'yes' or 'y' . Otherwise playAgain() will return False .
If playAgain() returns False , then the if statement's condition is True (because of
the not operator that reverses the Boolean value) and we execute the break statement. That
breaks us out of the while loop that was started on line 142. But there are no more lines of
code after that while-block, so the program terminates.