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Fixed bugs in games.py #380

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Merged
merged 5 commits into from
Mar 22, 2017
Merged

Fixed bugs in games.py #380

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32e5efe
move play_game into games class
KaiRawal Mar 18, 2017
e60f767
display current state before prompting for action
KaiRawal Mar 18, 2017
2f364b8
fixed player swap bug
KaiRawal Mar 18, 2017
3a820f2
display available moves to human players
KaiRawal Mar 18, 2017
2e18e77
make tests pass
KaiRawal Mar 21, 2017
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31 changes: 18 additions & 13 deletions games.py
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,10 @@ def min_value(state, alpha, beta, depth):

def query_player(game, state):
"""Make a move by querying standard input."""
print("current state:")
game.display(state)
print("available moves: {}".format(game.actions(state)))
print("")
move_string = input('Your move? ')
try:
move = eval(move_string)
Expand All @@ -153,18 +157,6 @@ def alphabeta_player(game, state):
return alphabeta_full_search(state, game)


def play_game(game, *players):
"""Play an n-person, move-alternating game."""

state = game.initial
while True:
for player in players:
move = player(game, state)
state = game.result(state, move)
if game.terminal_test(state):
game.display(state)
return game.utility(state, game.to_move(game.initial))

# ______________________________________________________________________________
# Some Sample Games

Expand Down Expand Up @@ -204,6 +196,17 @@ def display(self, state):

def __repr__(self):
return '<{}>'.format(self.__class__.__name__)

def play_game(self, *players):
"""Play an n-person, move-alternating game."""
state = self.initial
while True:
for player in players:
move = player(self, state)
state = self.result(state, move)
if self.terminal_test(state):
self.display(state)
return self.utility(state, self.to_move(self.initial))


class Fig52Game(Game):
Expand Down Expand Up @@ -255,7 +258,9 @@ def actions(self, state):

def result(self, state, move):
if move not in state.moves:
return state # Illegal move has no effect
return GameState(to_move=('O' if state.to_move == 'X' else 'X'),
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I'll accept this for now, but in general, this isn't right: the to_move need not be 'O' and 'X' in other games.

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Yes, I agree completely. I wondered the same thing. There were two reasons I chose such an implementation:

  1. this result function is specific to the TicTacToe class, which inherits from Game - and thus won't apply to other Game classes. The TicTacToe class specifically mentions that the only valid states are 'X' and 'O' here.
  2. the same approach had already been used in the function, in line 268 below.

However, I would be happy to discuss alternative implementations. Maybe we could have a turn function defined in the Game class itself, which could then be appropriately overridden in all subclasses (including TicTacTow), thus effectively generalising this part of the code.

utility=self.compute_utility(state.board, move, state.to_move),
board=state.board, moves=state.moves) # Illegal move has no effect
board = state.board.copy()
board[move] = state.to_move
moves = list(state.moves)
Expand Down
6 changes: 3 additions & 3 deletions tests/test_games.py
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Original file line number Diff line number Diff line change
Expand Up @@ -60,13 +60,13 @@ def test_alphabeta_full_search():


def test_random_tests():
assert play_game(Fig52Game(), alphabeta_player, alphabeta_player) == 3
assert Fig52Game().play_game(alphabeta_player, alphabeta_player) == 3

# The player 'X' (one who plays first) in TicTacToe never loses:
assert play_game(ttt, alphabeta_player, alphabeta_player) >= 0
assert ttt.play_game(alphabeta_player, alphabeta_player) >= 0

# The player 'X' (one who plays first) in TicTacToe never loses:
assert play_game(ttt, alphabeta_player, random_player) >= 0
assert ttt.play_game(alphabeta_player, random_player) >= 0


if __name__ == '__main__':
Expand Down