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Finished TicTacToe AI
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Lines changed: 121 additions & 31 deletions

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‎Chapter8/minimax.py‎

Lines changed: 3 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,6 @@
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# limitations under the License.
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from __future__ import annotations
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from typing import List
18-
from sys import float_info
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from board import Piece, Board, Move
2019

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@@ -27,13 +26,13 @@ def minimax(board: Board, maximizing: bool, original_player: Piece) -> float:
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2827
# Recursive case - maximize your gains or minimize the opponent's gains
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if maximizing:
30-
best_eval: float = float_info.min # arbitrarily low starting point
29+
best_eval: float = float("-inf") # arbitrarily low starting point
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for move in board.legal_moves:
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result: float = minimax(board.move(move), False, original_player)
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best_eval = max(result, best_eval)
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return best_eval
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else: # minimizing
36-
worst_eval: float = float_info.max
35+
worst_eval: float = float("inf")
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for move in board.legal_moves:
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result = minimax(board.move(move), True, original_player)
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worst_eval = min(result, worst_eval)
@@ -42,7 +41,7 @@ def minimax(board: Board, maximizing: bool, original_player: Piece) -> float:
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# Run minimax() on every possible move to find the best one
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def find_best_move(board: Board) -> Move:
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best_eval: float = float_info.min
44+
best_eval: float = float("-inf")
4645
best_move: Move = Move(-1)
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for move in board.legal_moves:
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result: float = minimax(board.move(move), False, board.turn)

‎Chapter8/tictactoe.py‎

Lines changed: 7 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@
2323
class TTTPiece(Piece, Enum):
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X = "X"
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O = "O"
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E = "E" # stand-in for empty
26+
E = " " # stand-in for empty
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@property
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def opposite(self) -> Piece:
@@ -73,29 +73,9 @@ def evaluate(self, player: Piece) -> float:
7373
else:
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return 0
7575

76-
77-
if __name__ == "__main__":
78-
from minimax import find_best_move
79-
# win in 1 move
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to_win_easy_position: List[TTTPiece] = [TTTPiece.X, TTTPiece.O, TTTPiece.X,
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TTTPiece.X, TTTPiece.E, TTTPiece.O,
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TTTPiece.E, TTTPiece.E, TTTPiece.O]
83-
test_board1: TTTBoard = TTTBoard(to_win_easy_position, TTTPiece.X)
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answer1: Move = find_best_move(test_board1)
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print(answer1)
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87-
# must block O's win
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to_block_position: List[TTTPiece] = [TTTPiece.X, TTTPiece.E, TTTPiece.E,
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TTTPiece.E, TTTPiece.E, TTTPiece.O,
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TTTPiece.E, TTTPiece.X, TTTPiece.O]
91-
test_board2: TTTBoard = TTTBoard(to_block_position, TTTPiece.X)
92-
answer2: Move = find_best_move(test_board2)
93-
print(answer2)
94-
95-
# find the best move to win 2 moves
96-
to_win_hard_position: List[TTTPiece] = [TTTPiece.X, TTTPiece.E, TTTPiece.E,
97-
TTTPiece.E, TTTPiece.E, TTTPiece.O,
98-
TTTPiece.O, TTTPiece.X, TTTPiece.E]
99-
test_board3: TTTBoard = TTTBoard(to_win_hard_position, TTTPiece.X)
100-
answer3: Move = find_best_move(test_board3)
101-
print(answer3)
76+
def __repr__(self) -> str:
77+
return f"""{self.position[0]}|{self.position[1]}|{self.position[2]}
78+
-----
79+
{self.position[3]}|{self.position[4]}|{self.position[5]}
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-----
81+
{self.position[6]}|{self.position[7]}|{self.position[8]}"""

‎Chapter8/tictactoe_ai.py‎

Lines changed: 57 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,57 @@
1+
# tictactoe_ai.py
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# From Classic Computer Science Problems in Python Chapter 8
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# Copyright 2018 David Kopec
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
6+
# you may not use this file except in compliance with the License.
7+
# You may obtain a copy of the License at
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#
9+
# http://www.apache.org/licenses/LICENSE-2.0
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#
11+
# Unless required by applicable law or agreed to in writing, software
12+
# distributed under the License is distributed on an "AS IS" BASIS,
13+
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14+
# See the License for the specific language governing permissions and
15+
# limitations under the License.
16+
from typing import List
17+
from minimax import find_best_move
18+
from tictactoe import TTTPiece, TTTBoard
19+
from board import Move
20+
21+
start_position: List[TTTPiece] = [TTTPiece.E, TTTPiece.E, TTTPiece.E,
22+
TTTPiece.E, TTTPiece.E, TTTPiece.E,
23+
TTTPiece.E, TTTPiece.E, TTTPiece.E]
24+
board: TTTBoard = TTTBoard(start_position, TTTPiece.X)
25+
26+
27+
def get_player_move() -> Move:
28+
player_move: Move = Move(-1)
29+
while player_move not in board.legal_moves:
30+
play: int = int(input("Enter a legal square (0-8):"))
31+
player_move = Move(play)
32+
return player_move
33+
34+
35+
if __name__ == "__main__":
36+
# main game loop
37+
while True:
38+
human_move: Move = get_player_move()
39+
board = board.move(human_move)
40+
if board.is_win:
41+
print("Human wins!")
42+
break
43+
elif board.is_draw:
44+
print("Draw!")
45+
break
46+
computer_move: Move = find_best_move(board)
47+
print(f"Computer move is {computer_move}")
48+
board = board.move(computer_move)
49+
print(board)
50+
if board.is_win:
51+
print("Computer wins!")
52+
break
53+
elif board.is_draw:
54+
print("Draw!")
55+
break
56+
57+

‎Chapter8/tictactoe_tests.py‎

Lines changed: 54 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,54 @@
1+
# tictactoe_tests.py
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# From Classic Computer Science Problems in Python Chapter 8
3+
# Copyright 2018 David Kopec
4+
#
5+
# Licensed under the Apache License, Version 2.0 (the "License");
6+
# you may not use this file except in compliance with the License.
7+
# You may obtain a copy of the License at
8+
#
9+
# http://www.apache.org/licenses/LICENSE-2.0
10+
#
11+
# Unless required by applicable law or agreed to in writing, software
12+
# distributed under the License is distributed on an "AS IS" BASIS,
13+
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14+
# See the License for the specific language governing permissions and
15+
# limitations under the License.
16+
import unittest
17+
from minimax import find_best_move
18+
from tictactoe import TTTPiece, TTTBoard
19+
from board import Move
20+
21+
22+
class TTTMinimaxTestCase(unittest.TestCase):
23+
def test_easy_position(self):
24+
# win in 1 move
25+
to_win_easy_position: List[TTTPiece] = [TTTPiece.X, TTTPiece.O, TTTPiece.X,
26+
TTTPiece.X, TTTPiece.E, TTTPiece.O,
27+
TTTPiece.E, TTTPiece.E, TTTPiece.O]
28+
test_board1: TTTBoard = TTTBoard(to_win_easy_position, TTTPiece.X)
29+
answer1: Move = find_best_move(test_board1)
30+
self.assertEqual(answer1, 6)
31+
32+
def test_block_position(self):
33+
# must block O's win
34+
to_block_position: List[TTTPiece] = [TTTPiece.X, TTTPiece.E, TTTPiece.E,
35+
TTTPiece.E, TTTPiece.E, TTTPiece.O,
36+
TTTPiece.E, TTTPiece.X, TTTPiece.O]
37+
test_board2: TTTBoard = TTTBoard(to_block_position, TTTPiece.X)
38+
answer2: Move = find_best_move(test_board2)
39+
self.assertEqual(answer2, 2)
40+
41+
def test_hard_position(self):
42+
# find the best move to win 2 moves
43+
to_win_hard_position: List[TTTPiece] = [TTTPiece.X, TTTPiece.E, TTTPiece.E,
44+
TTTPiece.E, TTTPiece.E, TTTPiece.O,
45+
TTTPiece.O, TTTPiece.X, TTTPiece.E]
46+
test_board3: TTTBoard = TTTBoard(to_win_hard_position, TTTPiece.X)
47+
answer3: Move = find_best_move(test_board3)
48+
self.assertEqual(answer3, 1)
49+
50+
51+
if __name__ == '__main__':
52+
unittest.main()
53+
54+

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