## Python

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Function Variable Posted by Garrett85 on 10 Oct 2009 at 9:39 AM
In the follwoing program I am having trouble understanding this function.
```def ask_yes_no(question):
"""Ask a yes or no question."""
response = None
while response not in ("y", "n"):
response = raw_input(question).lower()
return response```

Shouldn't question be response, or response be question? I know thought question was just a variable that held that date sent to the function.

```# Tic-Tac-Toe
# Plays the game of tic-tac-toe against a human opponent

# global constants
X = "X"
O = "O"
EMPTY = " "
TIE = "TIE"
NUM_SQUARES = 9

def display_instruct():
"""Display game instructions."""
print \
"""
Welcome to the greatest intellectual challenge of all time: Tic-Tac-Toe.
This will be a showdown between your human brain and my silicon processor.

You will make your move known by entering a number, 0 - 8.  The number
will correspond to the board position as illustrated:

0 | 1 | 2
---------
3 | 4 | 5
---------
6 | 7 | 8

Prepare yourself, human.  The ultimate battle is about to begin. \n
"""

"""Ask a yes or no question."""
response = None
while response not in ("y", "n"):
response = raw_input(question).lower()
return response

def ask_number(question, low, high):
"""Ask for a number within a range."""
response = None
while response not in range(low, high):
response = int(raw_input(question))
return response

def pieces():
"""Determine if player or computer goes first."""
go_first = ask_yes_no("Do you require the first move? (y/n): ")
if go_first == "y":
print "\nThen take the first move.  You will need it."
human = X
computer = O
else:
print "\nYour bravery will be your undoing... I will go first."
computer = X
human = O
return computer, human

def new_board():
"""Create new game board."""
board = []
for square in range(NUM_SQUARES):
board.append(EMPTY)
return board

def display_board(board):
"""Display game board on screen."""
print "\n\t", board[0], "|", board[1], "|", board[2]
print "\t", "---------"
print "\t", board[3], "|", board[4], "|", board[5]
print "\t", "---------"
print "\t", board[6], "|", board[7], "|", board[8], "\n"

def legal_moves(board):
"""Create list of legal moves."""
moves = []
for square in range(NUM_SQUARES):
if board[square] == EMPTY:
moves.append(square)
return moves

def winner(board):
"""Determine the game winner."""
WAYS_TO_WIN = ((0, 1, 2),
(3, 4, 5),
(6, 7, 8),
(0, 3, 6),
(1, 4, 7),
(2, 5, 8),
(0, 4, 8),
(2, 4, 6))

for row in WAYS_TO_WIN:
if board[row[0]] == board[row[1]] == board[row[2]] != EMPTY:
winner = board[row[0]]
return winner

if EMPTY not in board:
return TIE

return None

def human_move(board, human):
"""Get human move."""
legal = legal_moves(board)
move = None
while move not in legal:
move = ask_number("Where will you move? (0 - 8):", 0, NUM_SQUARES)
if move not in legal:
print "\nThat square is already occupied, foolish human.  Choose another.\n"
print "Fine..."
return move

def computer_move(board, computer, human):
"""Make computer move."""
# make a copy to work with since function will be changing list
board = board[:]
# the best positions to have, in order
BEST_MOVES = (4, 0, 2, 6, 8, 1, 3, 5, 7)

print "I shall take square number",

# if computer can win, take that move
for move in legal_moves(board):
board[move] = computer
if winner(board) == computer:
print move
return move
# done checking this move, undo it
board[move] = EMPTY

# if human can win, block that move
for move in legal_moves(board):
board[move] = human
if winner(board) == human:
print move
return move
# done checkin this move, undo it
board[move] = EMPTY

# since no one can win on next move, pick best open square
for move in BEST_MOVES:
if move in legal_moves(board):
print move
return move

def next_turn(turn):
"""Switch turns."""
if turn == X:
return O
else:
return X

def congrat_winner(the_winner, computer, human):
"""Congratulate the winner."""
if the_winner != TIE:
print the_winner, "won!\n"
else:
print "It's a tie!\n"

if the_winner == computer:
print "As I predicted, human, I am triumphant once more.  \n" \
"Proof that computers are superior to humans in all regards."

elif the_winner == human:
print "No, no!  It cannot be!  Somehow you tricked me, human. \n" \
"But never again!  I, the computer, so swears it!"

elif the_winner == TIE:
print "You were most lucky, human, and somehow managed to tie me.  \n" \
"Celebrate today... for this is the best you will ever achieve."

def main():
display_instruct()
computer, human = pieces()
turn = X
board = new_board()
display_board(board)

while not winner(board):
if turn == human:
move = human_move(board, human)
board[move] = human
else:
move = computer_move(board, computer, human)
board[move] = computer
display_board(board)
turn = next_turn(turn)

the_winner = winner(board)
congrat_winner(the_winner, computer, human)

# start the program
main()
raw_input("\n\nPress the enter key to quit.")```

Garrett85 Function Variable on 10 Oct 2009 at 9:39 AM
bubbatremell Re: Function Variable on 22 Oct 2009 at 1:16 PM

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