python-chess: a pure Python chess library¶
Introduction¶
python-chess is a pure Python chess library with move generation, move validation and support for common formats. This is the Scholar’s mate in python-chess:
>>> import chess
>>> board = chess.Board()
>>> board.legal_moves
<LegalMoveGenerator at ... (Nh3, Nf3, Nc3, Na3, h3, g3, f3, e3, d3, c3, ...)>
>>> chess.Move.from_uci("a8a1") in board.legal_moves
False
>>> board.push_san("e4")
Move.from_uci('e2e4')
>>> board.push_san("e5")
Move.from_uci('e7e5')
>>> board.push_san("Qh5")
Move.from_uci('d1h5')
>>> board.push_san("Nc6")
Move.from_uci('b8c6')
>>> board.push_san("Bc4")
Move.from_uci('f1c4')
>>> board.push_san("Nf6")
Move.from_uci('g8f6')
>>> board.push_san("Qxf7")
Move.from_uci('h5f7')
>>> board.is_checkmate()
True
>>> board
Board('r1bqkb1r/pppp1Qpp/2n2n2/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR b KQkq - 0 4')
Features¶
Supports Python 3.4+ and PyPy3.
IPython/Jupyter Notebook integration. SVG rendering docs.
>>> board
Chess variants: Standard, Chess960, Suicide, Giveaway, Atomic, King of the Hill, Racing Kings, Horde, Three-check, Crazyhouse. Variant docs.
Make and unmake moves.
>>> Nf3 = chess.Move.from_uci("g1f3") >>> board.push(Nf3) # Make the move >>> board.pop() # Unmake the last move Move.from_uci('g1f3')
Show a simple ASCII board.
>>> board = chess.Board("r1bqkb1r/pppp1Qpp/2n2n2/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR b KQkq - 0 4") >>> print(board) r . b q k b . r p p p p . Q p p . . n . . n . . . . . . p . . . . . B . P . . . . . . . . . . . P P P P . P P P R N B . K . N R
Detects checkmates, stalemates and draws by insufficient material.
>>> board.is_stalemate() False >>> board.is_insufficient_material() False >>> board.is_game_over() True
Detects repetitions. Has a half-move clock.
>>> board.can_claim_threefold_repetition() False >>> board.halfmove_clock 0 >>> board.can_claim_fifty_moves() False >>> board.can_claim_draw() False
With the new rules from July 2014, a game ends as a draw (even without a claim) once a fivefold repetition occurs or if there are 75 moves without a pawn push or capture. Other ways of ending a game take precedence.
>>> board.is_fivefold_repetition() False >>> board.is_seventyfive_moves() False
Detects checks and attacks.
>>> board.is_check() True >>> board.is_attacked_by(chess.WHITE, chess.E8) True >>> attackers = board.attackers(chess.WHITE, chess.F3) >>> attackers SquareSet(0x0000000000004040) >>> chess.G2 in attackers True >>> print(attackers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . 1 .
Parses and creates SAN representation of moves.
>>> board = chess.Board() >>> board.san(chess.Move(chess.E2, chess.E4)) 'e4' >>> board.parse_san('Nf3') Move.from_uci('g1f3') >>> board.variation_san([chess.Move.from_uci(m) for m in ["e2e4", "e7e5", "g1f3"]]) '1. e4 e5 2. Nf3'
Parses and creates FENs, extended FENs and Shredder FENs.
>>> board.fen() 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1' >>> board.shredder_fen() 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w HAha - 0 1' >>> board = chess.Board("8/8/8/2k5/4K3/8/8/8 w - - 4 45") >>> board.piece_at(chess.C5) Piece.from_symbol('k')
Parses and creates EPDs.
>>> board = chess.Board() >>> board.epd(bm=board.parse_uci("d2d4")) 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - bm d4;' >>> ops = board.set_epd("1k1r4/pp1b1R2/3q2pp/4p3/2B5/4Q3/PPP2B2/2K5 b - - bm Qd1+; id \"BK.01\";") >>> ops == {'bm': [chess.Move.from_uci('d6d1')], 'id': 'BK.01'} True
Detects absolute pins and their directions.
Reads Polyglot opening books. Docs.
>>> import chess.polyglot >>> book = chess.polyglot.open_reader("data/polyglot/performance.bin") >>> board = chess.Board() >>> main_entry = book.find(board) >>> main_entry.move() Move.from_uci('e2e4') >>> main_entry.weight 1 >>> main_entry.learn 0 >>> book.close()
Reads and writes PGNs. Supports headers, comments, NAGs and a tree of variations. Docs.
>>> import chess.pgn >>> with open("data/pgn/molinari-bordais-1979.pgn") as pgn: ... first_game = chess.pgn.read_game(pgn) >>> first_game.headers["White"] 'Molinari' >>> first_game.headers["Black"] 'Bordais' >>> first_game.mainline() <Mainline at ... (1. e4 c5 2. c4 Nc6 3. Ne2 Nf6 4. Nbc3 Nb4 5. g3 Nd3#)> >>> first_game.headers["Result"] '0-1'
Probe Gaviota endgame tablebases (DTM, WDL). Docs.
Probe Syzygy endgame tablebases (DTZ, WDL). Docs.
>>> import chess.syzygy >>> tablebase = chess.syzygy.open_tablebase("data/syzygy/regular") >>> # Black to move is losing in 53 half moves (distance to zero) in this >>> # KNBvK endgame. >>> board = chess.Board("8/2K5/4B3/3N4/8/8/4k3/8 b - - 0 1") >>> tablebase.probe_dtz(board) -53 >>> tablebase.close()
Communicate with an UCI engine. Docs.
>>> import chess.uci >>> engine = chess.uci.popen_engine("stockfish") >>> engine.uci() >>> engine.author 'Tord Romstad, Marco Costalba and Joona Kiiski' >>> # Synchronous mode. >>> board = chess.Board("1k1r4/pp1b1R2/3q2pp/4p3/2B5/4Q3/PPP2B2/2K5 b - - 0 1") >>> engine.position(board) >>> engine.go(movetime=2000) # Gets a tuple of bestmove and ponder move BestMove(bestmove=Move.from_uci('d6d1'), ponder=Move.from_uci('c1d1')) >>> # Asynchronous mode. >>> def callback(command): ... bestmove, ponder = command.result() ... assert bestmove == chess.Move.from_uci('d6d1') ... >>> command = engine.go(movetime=2000, async_callback=callback) >>> command.done() False >>> command.result() BestMove(bestmove=Move.from_uci('d6d1'), ponder=Move.from_uci('c1d1')) >>> command.done() True >>> # Quit. >>> engine.quit() 0
Selected use cases¶
If you like, let me know if you are creating something intresting with python-chess, for example:
- a stand-alone chess computer based on DGT board – http://www.picochess.org/
- a website to probe Syzygy endgame tablebases – https://syzygy-tables.info/
- a GUI to play against UCI chess engines – http://johncheetham.com/projects/jcchess/
- deep learning for Crazyhouse – https://github.com/QueensGambit/CrazyAra
- a command-line PGN annotator – https://github.com/rpdelaney/python-chess-annotator
- a bot to play chess on Telegram – https://github.com/cxjdavin/tgchessbot
- an HTTP microservice to render board images – https://github.com/niklasf/web-boardimage
- a bridge between Lichess API and chess engines – https://github.com/careless25/lichess-bot
- a JIT compiled chess engine – https://github.com/SamRagusa/Batch-First
Acknowledgements¶
Thanks to the Stockfish authors and thanks to Sam Tannous for publishing his approach to avoid rotated bitboards with direct lookup (PDF) alongside his GPL2+ engine Shatranj. Some move generation ideas are taken from these sources.
Thanks to Ronald de Man for his Syzygy endgame tablebases. The probing code in python-chess is very directly ported from his C probing code.
Thanks to Miguel A. Ballicora for his Gaviota tablebases. (I wish the generating code was free software.)
License¶
python-chess is licensed under the GPL 3 (or any later version at your option). Check out LICENSE.txt for the full text.
Contents¶
Core¶
Colors¶
Constants for the side to move or the color of a piece.
-
chess.
WHITE
= True¶
-
chess.
BLACK
= False¶
You can get the opposite color using not color
.
Piece types¶
-
chess.
PAWN
= 1¶
-
chess.
KNIGHT
= 2¶
-
chess.
BISHOP
= 3¶
-
chess.
ROOK
= 4¶
-
chess.
QUEEN
= 5¶
-
chess.
KING
= 6¶
Squares¶
-
chess.
A1
= 0¶
-
chess.
B1
= 1¶
and so on to
-
chess.
G8
= 62¶
-
chess.
H8
= 63¶
-
chess.
SQUARES
= [chess.A1, chess.B1, ..., chess.G8, chess.H8]¶
-
chess.
SQUARE_NAMES
= ['a1', 'b1', ..., 'g8', 'h8']¶
-
chess.
FILE_NAMES
= ['a', 'b', ..., 'g', 'h']¶
-
chess.
RANK_NAMES
= ['1', '2', ..., '7', '8']¶
-
chess.
square
(file_index, rank_index)¶ Gets a square number by file and rank index.
-
chess.
square_file
(square)¶ Gets the file index of the square where
0
is the a-file.
-
chess.
square_rank
(square)¶ Gets the rank index of the square where
0
is the first rank.
-
chess.
square_distance
(a, b)¶ Gets the distance (i.e., the number of king steps) from square a to b.
-
chess.
square_mirror
(square)¶ Mirrors the square vertically.
Pieces¶
-
class
chess.
Piece
(piece_type, color)¶ A piece with type and color.
-
piece_type
¶ The piece type.
-
color
¶ The piece color.
-
symbol
()¶ Gets the symbol
P
,N
,B
,R
,Q
orK
for white pieces or the lower-case variants for the black pieces.
-
unicode_symbol
(*, invert_color=False)¶ Gets the Unicode character for the piece.
-
Moves¶
-
class
chess.
Move
(from_square, to_square, promotion=None, drop=None)¶ Represents a move from a square to a square and possibly the promotion piece type.
Drops and null moves are supported.
-
from_square
¶ The source square.
-
to_square
¶ The target square.
-
promotion
¶ The promotion piece type or
Ǹone
.
-
drop
¶ The drop piece type or
None
.
-
uci
()¶ Gets an UCI string for the move.
For example, a move from a7 to a8 would be
a7a8
ora7a8q
(if the latter is a promotion to a queen).The UCI representation of a null move is
0000
.
-
classmethod
from_uci
(uci)¶ Parses an UCI string.
Raises: ValueError
if the UCI string is invalid.
-
classmethod
null
()¶ Gets a null move.
A null move just passes the turn to the other side (and possibly forfeits en passant capturing). Null moves evaluate to
False
in boolean contexts.>>> import chess >>> >>> bool(chess.Move.null()) False
-
Board¶
-
chess.
STARTING_FEN
= 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1'¶ The FEN for the standard chess starting position.
-
chess.
STARTING_BOARD_FEN
= 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR'¶ The board part of the FEN for the standard chess starting position.
-
class
chess.
Board
(fen='rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1', *, chess960=False)¶ A
BaseBoard
and additional information representing a chess position.Provides move generation, validation, parsing, attack generation, game end detection, move counters and the capability to make and unmake moves.
The board is initialized to the standard chess starting position, unless otherwise specified in the optional fen argument. If fen is
None
, an empty board is created.Optionally supports chess960. In Chess960 castling moves are encoded by a king move to the corresponding rook square. Use
chess.Board.from_chess960_pos()
to create a board with one of the Chess960 starting positions.It’s safe to set
turn
,castling_rights
,ep_square
,halfmove_clock
andfullmove_number
directly.-
turn
¶ The side to move.
-
castling_rights
¶ Bitmask of the rooks with castling rights.
To test for specific squares:
>>> import chess >>> >>> board = chess.Board() >>> bool(board.castling_rights & chess.BB_H1) # White can castle with the h1 rook True
To add a specific square:
>>> board.castling_rights |= chess.BB_A1
Use
set_castling_fen()
to set multiple castling rights. Also seehas_castling_rights()
,has_kingside_castling_rights()
,has_queenside_castling_rights()
,has_chess960_castling_rights()
,clean_castling_rights()
.
-
ep_square
¶ The potential en passant square on the third or sixth rank or
None
.Use
has_legal_en_passant()
to test if en passant capturing would actually be possible on the next move.
-
fullmove_number
¶ Counts move pairs. Starts at 1 and is incremented after every move of the black side.
-
halfmove_clock
¶ The number of half-moves since the last capture or pawn move.
-
promoted
¶ A bitmask of pieces that have been promoted.
-
chess960
¶ Whether the board is in Chess960 mode. In Chess960 castling moves are represented as king moves to the corresponding rook square.
-
legal_moves
= LegalMoveGenerator(self)¶ A dynamic list of legal moves.
>>> import chess >>> >>> board = chess.Board() >>> board.legal_moves.count() 20 >>> bool(board.legal_moves) True >>> move = chess.Move.from_uci("g1f3") >>> move in board.legal_moves True
Wraps
generate_legal_moves()
andis_legal()
.
-
pseudo_legal_moves
= PseudoLegalMoveGenerator(self)¶ A dynamic list of pseudo legal moves, much like the legal move list.
Pseudo legal moves might leave or put the king in check, but are otherwise valid. Null moves are not pseudo legal. Castling moves are only included if they are completely legal.
Wraps
generate_pseudo_legal_moves()
andis_pseudo_legal()
.
-
move_stack
¶ The move stack. Use
Board.push()
,Board.pop()
,Board.peek()
andBoard.clear_stack()
for manipulation.
-
reset
()¶ Restores the starting position.
-
clear
()¶ Clears the board.
Resets move stack and move counters. The side to move is white. There are no rooks or kings, so castling rights are removed.
In order to be in a valid
status()
at least kings need to be put on the board.
-
clear_board
()¶ Clears the board.
-
clear_stack
()¶ Clears the move stack.
-
root
()¶ Returns a copy of the root position.
-
remove_piece_at
(square)¶ Removes the piece from the given square. Returns the
Piece
orNone
if the square was already empty.
-
set_piece_at
(square, piece, promoted=False)¶ Sets a piece at the given square.
An existing piece is replaced. Setting piece to
None
is equivalent toremove_piece_at()
.
-
is_check
()¶ Returns if the current side to move is in check.
-
is_into_check
(move)¶ Checks if the given move would leave the king in check or put it into check. The move must be at least pseudo legal.
-
was_into_check
()¶ Checks if the king of the other side is attacked. Such a position is not valid and could only be reached by an illegal move.
-
is_variant_end
()¶ Checks if the game is over due to a special variant end condition.
Note, for example, that stalemate is not considered a variant-specific end condition (this method will return
False
), yet it can have a special result in suicide chess (any ofis_variant_loss()
,is_variant_win()
,is_variant_draw()
might returnTrue
).
-
is_variant_loss
()¶ Checks if a special variant-specific loss condition is fulfilled.
-
is_variant_win
()¶ Checks if a special variant-specific win condition is fulfilled.
-
is_variant_draw
()¶ Checks if a special variant-specific drawing condition is fulfilled.
-
is_game_over
(*, claim_draw=False)¶ Checks if the game is over due to
checkmate
,stalemate
,insufficient material
, theseventyfive-move rule
,fivefold repetition
or avariant end condition
.The game is not considered to be over by the
fifty-move rule
orthreefold repetition
, unless claim_draw is given. Note that checking the latter can be slow.
-
result
(*, claim_draw=False)¶ Gets the game result.
1-0
,0-1
or1/2-1/2
if thegame is over
. Otherwise, the result is undetermined:*
.
-
is_checkmate
()¶ Checks if the current position is a checkmate.
-
is_stalemate
()¶ Checks if the current position is a stalemate.
-
is_insufficient_material
()¶ Checks for a draw due to insufficient mating material.
-
is_seventyfive_moves
()¶ Since the 1st of July 2014, a game is automatically drawn (without a claim by one of the players) if the half-move clock since a capture or pawn move is equal to or grather than 150. Other means to end a game take precedence.
-
is_fivefold_repetition
()¶ Since the 1st of July 2014 a game is automatically drawn (without a claim by one of the players) if a position occurs for the fifth time. Originally this had to occur on consecutive alternating moves, but this has since been revised.
-
can_claim_draw
()¶ Checks if the side to move can claim a draw by the fifty-move rule or by threefold repetition.
Note that checking the latter can be slow.
-
can_claim_fifty_moves
()¶ Draw by the fifty-move rule can be claimed once the clock of halfmoves since the last capture or pawn move becomes equal or greater to 100 and the side to move still has a legal move they can make.
-
can_claim_threefold_repetition
()¶ Draw by threefold repetition can be claimed if the position on the board occured for the third time or if such a repetition is reached with one of the possible legal moves.
Note that checking this can be slow: In the worst case scenario every legal move has to be tested and the entire game has to be replayed because there is no incremental transposition table.
-
push
(move)¶ Updates the position with the given move and puts it onto the move stack.
>>> import chess >>> >>> board = chess.Board() >>> >>> Nf3 = chess.Move.from_uci("g1f3") >>> board.push(Nf3) # Make the move
>>> board.pop() # Unmake the last move Move.from_uci('g1f3')
Null moves just increment the move counters, switch turns and forfeit en passant capturing.
Warning: Moves are not checked for legality.
-
pop
()¶ Restores the previous position and returns the last move from the stack.
Raises: IndexError
if the stack is empty.
-
peek
()¶ Gets the last move from the move stack.
Raises: IndexError
if the move stack is empty.
-
has_pseudo_legal_en_passant
()¶ Checks if there is a pseudo-legal en passant capture.
-
has_legal_en_passant
()¶ Checks if there is a legal en passant capture.
-
fen
(*, shredder=False, en_passant='legal', promoted=None)¶ Gets a FEN representation of the position.
A FEN string (e.g.,
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
) consists of the position partboard_fen()
, theturn
, the castling part (castling_rights
), the en passant square (ep_square
), thehalfmove_clock
and thefullmove_number
.Parameters: - shredder – Use
castling_shredder_fen()
and encode castling rights by the file of the rook (likeHAha
) instead of the defaultcastling_xfen()
(likeKQkq
). - en_passant – By default, only fully legal en passant squares
are included (
has_legal_en_passant()
). Passfen
to strictly follow the FEN specification (always include the en passant square after a two-step pawn move) orxfen
to follow the X-FEN specification (has_pseudo_legal_en_passant()
). - promoted – Mark promoted pieces like
Q~
. By default, this is only enabled in chess variants where this is relevant.
- shredder – Use
-
set_fen
(fen)¶ Parses a FEN and sets the position from it.
Raises: ValueError
if the FEN string is invalid.
-
set_castling_fen
(castling_fen)¶ Sets castling rights from a string in FEN notation like
Qqk
.Raises: ValueError
if the castling FEN is syntactically invalid.
-
set_board_fen
(fen)¶ Parses a FEN and sets the board from it.
Raises: ValueError
if the FEN string is invalid.
-
set_chess960_pos
(sharnagl)¶ Sets up a Chess960 starting position given its index between 0 and 959. Also see
from_chess960_pos()
.
-
chess960_pos
(*, ignore_turn=False, ignore_castling=False, ignore_counters=True)¶ Gets the Chess960 starting position index between 0 and 956 or
None
if the current position is not a Chess960 starting position.By default white to move (ignore_turn) and full castling rights (ignore_castling) are required, but move counters (ignore_counters) are ignored.
-
epd
(*, shredder=False, en_passant='legal', promoted=None, **operations)¶ Gets an EPD representation of the current position.
See
fen()
for FEN formatting options (shredder, ep_square and promoted).EPD operations can be given as keyword arguments. Supported operands are strings, integers, floats, moves, lists of moves and
None
. All other operands are converted to strings.A list of moves for pv will be interpreted as a variation. All other move lists are interpreted as a set of moves in the current position.
hmvc and fmvc are not included by default. You can use:
>>> import chess >>> >>> board = chess.Board() >>> board.epd(hmvc=board.halfmove_clock, fmvc=board.fullmove_number) 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - hmvc 0; fmvc 1;'
-
set_epd
(epd)¶ Parses the given EPD string and uses it to set the position.
If present,
hmvc
andfmvn
are used to set the half-move clock and the full-move number. Otherwise,0
and1
are used.Returns a dictionary of parsed operations. Values can be strings, integers, floats, move objects, or lists of moves.
Raises: ValueError
if the EPD string is invalid.
-
san
(move)¶ Gets the standard algebraic notation of the given move in the context of the current position.
-
lan
(move)¶ Gets the long algebraic notation of the given move in the context of the current position.
-
variation_san
(variation)¶ Given a sequence of moves, returns a string representing the sequence in standard algebraic notation (e.g.,
1. e4 e5 2. Nf3 Nc6
or37...Bg6 38. fxg6
).The board will not be modified as a result of calling this.
Raises: ValueError
if any moves in the sequence are illegal.
-
parse_san
(san)¶ Uses the current position as the context to parse a move in standard algebraic notation and returns the corresponding move object.
The returned move is guaranteed to be either legal or a null move.
Raises: ValueError
if the SAN is invalid or ambiguous.
-
push_san
(san)¶ Parses a move in standard algebraic notation, makes the move and puts it on the the move stack.
Returns the move.
Raises: ValueError
if neither legal nor a null move.
-
uci
(move, *, chess960=None)¶ Gets the UCI notation of the move.
chess960 defaults to the mode of the board. Pass
True
to force Chess960 mode.
-
parse_uci
(uci)¶ Parses the given move in UCI notation.
Supports both Chess960 and standard UCI notation.
The returned move is guaranteed to be either legal or a null move.
Raises: ValueError
if the move is invalid or illegal in the current position (but not a null move).
-
push_uci
(uci)¶ Parses a move in UCI notation and puts it on the move stack.
Returns the move.
Raises: ValueError
if the move is invalid or illegal in the current position (but not a null move).
-
is_en_passant
(move)¶ Checks if the given pseudo-legal move is an en passant capture.
-
is_capture
(move)¶ Checks if the given pseudo-legal move is a capture.
-
is_zeroing
(move)¶ Checks if the given pseudo-legal move is a capture or pawn move.
-
is_irreversible
(move)¶ Checks if the given pseudo-legal move is irreversible.
In standard chess, pawn moves, captures and moves that destroy castling rights are irreversible.
-
is_castling
(move)¶ Checks if the given pseudo-legal move is a castling move.
-
is_kingside_castling
(move)¶ Checks if the given pseudo-legal move is a kingside castling move.
-
is_queenside_castling
(move)¶ Checks if the given pseudo-legal move is a queenside castling move.
-
clean_castling_rights
()¶ Returns valid castling rights filtered from
castling_rights
.
-
has_castling_rights
(color)¶ Checks if the given side has castling rights.
-
has_kingside_castling_rights
(color)¶ Checks if the given side has kingside (that is h-side in Chess960) castling rights.
-
has_queenside_castling_rights
(color)¶ Checks if the given side has queenside (that is a-side in Chess960) castling rights.
-
has_chess960_castling_rights
()¶ Checks if there are castling rights that are only possible in Chess960.
-
status
()¶ Gets a bitmask of possible problems with the position.
Move making, generation and validation are only guaranteed to work on a completely valid board.
STATUS_VALID
for a completely valid board.Otherwise, bitwise combinations of:
STATUS_NO_WHITE_KING
,STATUS_NO_BLACK_KING
,STATUS_TOO_MANY_KINGS
,STATUS_TOO_MANY_WHITE_PAWNS
,STATUS_TOO_MANY_BLACK_PAWNS
,STATUS_PAWNS_ON_BACKRANK
,STATUS_TOO_MANY_WHITE_PIECES
,STATUS_TOO_MANY_BLACK_PIECES
,STATUS_BAD_CASTLING_RIGHTS
,STATUS_INVALID_EP_SQUARE
,STATUS_OPPOSITE_CHECK
,STATUS_EMPTY
,STATUS_RACE_CHECK
,STATUS_RACE_OVER
,STATUS_RACE_MATERIAL
.
-
is_valid
()¶ Checks if the board is valid.
Move making, generation and validation are only guaranteed to work on a completely valid board.
See
status()
for details.
-
mirror
()¶ Returns a mirrored copy of the board.
The board is mirrored vertically and piece colors are swapped, so that the position is equivalent modulo color.
-
copy
(*, stack=True)¶ Creates a copy of the board.
-
classmethod
from_epd
(epd, *, chess960=False)¶ Creates a new board from an EPD string. See
set_epd()
.Returns the board and the dictionary of parsed operations as a tuple.
-
classmethod
from_chess960_pos
(sharnagl)¶ Creates a new board, initialized with a Chess960 starting position.
>>> import chess >>> import random >>> >>> board = chess.Board.from_chess960_pos(random.randint(0, 959))
-
-
class
chess.
BaseBoard
(board_fen='rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR')¶ A board representing the position of chess pieces. See
Board
for a full board with move generation.The board is initialized with the standard chess starting position, unless otherwise specified in the optional board_fen argument. If board_fen is
None
, an empty board is created.-
clear_board
()¶ Clears the board.
-
pieces
(piece_type, color)¶ Gets pieces of the given type and color.
Returns a
set of squares
.
-
piece_type_at
(square)¶ Gets the piece type at the given square.
-
king
(color)¶ Finds the king square of the given side. Returns
None
if there is no king of that color.In variants with king promotions, only non-promoted kings are considered.
-
attacks
(square)¶ Gets a set of attacked squares from a given square.
There will be no attacks if the square is empty. Pinned pieces are still attacking other squares.
Returns a
set of squares
.
-
is_attacked_by
(color, square)¶ Checks if the given side attacks the given square.
Pinned pieces still count as attackers. Pawns that can be captured en passant are not considered attacked.
-
attackers
(color, square)¶ Gets a set of attackers of the given color for the given square.
Pinned pieces still count as attackers.
Returns a
set of squares
.
-
pin
(color, square)¶ Detects an absolute pin (and its direction) of the given square to the king of the given color.
>>> import chess >>> >>> board = chess.Board("rnb1k2r/ppp2ppp/5n2/3q4/1b1P4/2N5/PP3PPP/R1BQKBNR w KQkq - 3 7") >>> board.is_pinned(chess.WHITE, chess.C3) True >>> direction = board.pin(chess.WHITE, chess.C3) >>> direction SquareSet(0x0000000102040810) >>> print(direction) . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . 1 . . . . . . . . 1 . . . . . . . . 1 . . . . . . . . 1 . . .
Returns a
set of squares
that mask the rank, file or diagonal of the pin. If there is no pin, then a mask of the entire board is returned.
-
is_pinned
(color, square)¶ Detects if the given square is pinned to the king of the given color.
-
remove_piece_at
(square)¶ Removes the piece from the given square. Returns the
Piece
orNone
if the square was already empty.
-
set_piece_at
(square, piece, promoted=False)¶ Sets a piece at the given square.
An existing piece is replaced. Setting piece to
None
is equivalent toremove_piece_at()
.
-
board_fen
(*, promoted=False)¶ Gets the board FEN.
-
set_board_fen
(fen)¶ Parses a FEN and sets the board from it.
Raises: ValueError
if the FEN string is invalid.
-
set_chess960_pos
(sharnagl)¶ Sets up a Chess960 starting position given its index between 0 and 959. Also see
from_chess960_pos()
.
-
chess960_pos
()¶ Gets the Chess960 starting position index between 0 and 959 or
None
.
-
unicode
(*, invert_color=False, borders=False)¶ Returns a string representation of the board with Unicode pieces. Useful for pretty-printing to a terminal.
Parameters: - invert_color – Invert color of the Unicode pieces.
- borders – Show borders and a coordinate margin.
-
mirror
()¶ Returns a mirrored copy of the board.
The board is mirrored vertically and piece colors are swapped, so that the position is equivalent modulo color.
-
copy
()¶ Creates a copy of the board.
-
classmethod
empty
()¶ Creates a new empty board. Also see
clear_board()
.
-
classmethod
from_chess960_pos
(sharnagl)¶ Creates a new board, initialized with a Chess960 starting position.
>>> import chess >>> import random >>> >>> board = chess.Board.from_chess960_pos(random.randint(0, 959))
-
Square sets¶
-
class
chess.
SquareSet
(squares=0)¶ A set of squares.
>>> import chess >>> >>> squares = chess.SquareSet(chess.BB_A8 | chess.BB_RANK_1) >>> squares SquareSet(0x01000000000000ff)
>>> print(squares) 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 1 1 1 1 1 1
>>> len(squares) 9
>>> bool(squares) True
>>> chess.B1 in squares True
>>> for square in squares: ... # 0 -- chess.A1 ... # 1 -- chess.B1 ... # 2 -- chess.C1 ... # 3 -- chess.D1 ... # 4 -- chess.E1 ... # 5 -- chess.F1 ... # 6 -- chess.G1 ... # 7 -- chess.H1 ... # 56 -- chess.A8 ... print(square) ... 0 1 2 3 4 5 6 7 56
>>> list(squares) [0, 1, 2, 3, 4, 5, 6, 7, 56]
Square sets are internally represented by 64-bit integer masks of the included squares. Bitwise operations can be used to compute unions, intersections and shifts.
>>> int(squares) 72057594037928191
Also supports common set operations like
issubset()
,issuperset()
,union()
,intersection()
,difference()
,symmetric_difference()
andcopy()
as well asupdate()
,intersection_update()
,difference_update()
,symmetric_difference_update()
andclear()
.-
add
(square)¶ Adds a square to the set.
-
discard
(square)¶ Discards a square from the set.
-
isdisjoint
(other)¶ Test if the square sets are disjoint.
-
issubset
(other)¶ Test if this square set is a subset of another.
-
issuperset
(other)¶ Test if this square set is a superset of another.
-
remove
(square)¶ Removes a square from the set.
Raises: KeyError
if the given square was not in the set.
-
pop
()¶ Removes a square from the set and returns it.
Raises: KeyError
on an empty set.
-
clear
()¶ Remove all elements from this set.
-
carry_rippler
()¶ Iterator over the subsets of this set.
-
mirror
()¶ Returns a vertically mirrored copy of this square set.
-
tolist
()¶ Convert the set to a list of 64 bools.
-
Common integer masks are:
-
chess.
BB_EMPTY
= 0¶
-
chess.
BB_ALL
= 0xFFFFFFFFFFFFFFFF¶
Single squares:
-
chess.
BB_SQUARES
= [chess.BB_A1, chess.BB_B1, ..., chess.BB_G8, chess.BB_H8]¶
Ranks and files:
-
chess.
BB_RANKS
= [chess.BB_RANK_1, ..., chess.BB_RANK_8]¶
-
chess.
BB_FILES
= [chess.BB_FILE_A, ..., chess.BB_FILE_H]¶
Other masks:
-
chess.
BB_LIGHT_SQUARES
= 0x55AA55AA55AA55AA¶
-
chess.
BB_DARK_SQUARES
= 0xAA55AA55AA55AA55¶
-
chess.
BB_BACKRANKS
= chess.BB_RANK_1 | chess.BB_RANK_8¶
-
chess.
BB_CORNERS
= chess.BB_A1 | chess.BB_H1 | chess.BB_A8 | chess.BB_H8¶
-
chess.
BB_CENTER
= chess.BB_D4 | chess.BB_E4 | chess.BB_D5 | chess.BB_E5¶
PGN parsing and writing¶
Parsing¶
-
chess.pgn.
read_game
(handle, *, Visitor=<class 'chess.pgn.GameCreator'>)¶ Reads a game from a file opened in text mode.
>>> import chess.pgn >>> >>> pgn = open("data/pgn/kasparov-deep-blue-1997.pgn") >>> >>> first_game = chess.pgn.read_game(pgn) >>> second_game = chess.pgn.read_game(pgn) >>> >>> first_game.headers["Event"] 'IBM Man-Machine, New York USA' >>> >>> # Iterate through all moves and play them on a board. >>> board = first_game.board() >>> for move in first_game.mainline_moves(): ... board.push(move) ... >>> board Board('4r3/6P1/2p2P1k/1p6/pP2p1R1/P1B5/2P2K2/3r4 b - - 0 45')
By using text mode, the parser does not need to handle encodings. It is the caller’s responsibility to open the file with the correct encoding. PGN files are usually ASCII or UTF-8 encoded. So, the following should cover most relevant cases (ASCII, UTF-8, UTF-8 with BOM).
>>> pgn = open("data/pgn/kasparov-deep-blue-1997.pgn", encoding="utf-8-sig")
Use
StringIO
to parse games from a string.>>> import io >>> >>> pgn = io.StringIO("1. e4 e5 2. Nf3 *") >>> game = chess.pgn.read_game(pgn)
The end of a game is determined by a completely blank line or the end of the file. (Of course, blank lines in comments are possible).
According to the PGN standard, at least the usual 7 header tags are required for a valid game. This parser also handles games without any headers just fine.
The parser is relatively forgiving when it comes to errors. It skips over tokens it can not parse. Any exceptions are logged and collected in
Game.errors
. This behavior can beoverriden
.Returns the parsed game or
None
if the end of file is reached.
Writing¶
If you want to export your game with all headers, comments and variations, you can do it like this:
>>> import chess
>>> import chess.pgn
>>>
>>> game = chess.pgn.Game()
>>> game.headers["Event"] = "Example"
>>> node = game.add_variation(chess.Move.from_uci("e2e4"))
>>> node = node.add_variation(chess.Move.from_uci("e7e5"))
>>> node.comment = "Comment"
>>>
>>> print(game)
[Event "Example"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
1. e4 e5 { Comment } *
Remember that games in files should be separated with extra blank lines.
>>> print(game, file=open("/dev/null", "w"), end="\n\n")
Use the StringExporter()
or
FileExporter()
visitors if you need more control.
Game model¶
Games are represented as a tree of moves. Each GameNode
can have extra
information, such as comments. The root node of a game
(Game
extends the GameNode
) also
holds general information, such as game headers.
-
class
chess.pgn.
Game
(headers=None)¶ The root node of a game with extra information such as headers and the starting position. Also has all the other properties and methods of
GameNode
.-
headers
¶ A mapping of headers. By default, the following 7 headers are provided:
>>> import chess.pgn >>> >>> game = chess.pgn.Game() >>> game.headers Headers(Event='?', Site='?', Date='????.??.??', Round='?', White='?', Black='?', Result='*')
-
errors
¶ A list of errors (such as illegal or ambiguous moves) encountered while parsing the game.
-
board
(*, _cache=False)¶ Gets the starting position of the game.
Unless the
FEN
header tag is set, this is the default starting position (for theVariant
).
-
setup
(board)¶ Sets up a specific starting position. This sets (or resets) the
FEN
,SetUp
, andVariant
header tags.
-
accept
(visitor)¶ Traverses the game in PGN order using the given visitor. Returns the visitor result.
-
classmethod
without_tag_roster
()¶ Creates an empty game without the default 7 tag roster.
-
-
class
chess.pgn.
GameNode
¶ -
parent
¶ The parent node or
None
if this is the root node of the game.
-
move
¶ The move leading to this node or
None
if this is the root node of the game.
-
nags
= set()¶ A set of NAGs as integers. NAGs always go behind a move, so the root node of the game will never have NAGs.
-
comment
= ''¶ A comment that goes behind the move leading to this node. Comments that occur before any moves are assigned to the root node.
-
starting_comment
= ''¶ A comment for the start of a variation. Only nodes that actually start a variation (
starts_variation()
checks this) can have a starting comment. The root node can not have a starting comment.
-
variations
¶ A list of child nodes.
-
board
(*, _cache=True)¶ Gets a board with the position of the node.
It’s a copy, so modifying the board will not alter the game.
-
san
()¶ Gets the standard algebraic notation of the move leading to this node. See
chess.Board.san()
.Do not call this on the root node.
-
uci
(*, chess960=None)¶ Gets the UCI notation of the move leading to this node. See
chess.Board.uci()
.Do not call this on the root node.
-
root
()¶ Gets the root node, i.e., the game.
-
end
()¶ Follows the main variation to the end and returns the last node.
-
is_end
()¶ Checks if this node is the last node in the current variation.
-
starts_variation
()¶ Checks if this node starts a variation (and can thus have a starting comment). The root node does not start a variation and can have no starting comment.
For example, in
1. e4 e5 (1... c5 2. Nf3) 2. Nf3
, the node holding 1… c5 starts a variation.
-
is_mainline
()¶ Checks if the node is in the mainline of the game.
-
is_main_variation
()¶ Checks if this node is the first variation from the point of view of its parent. The root node is also in the main variation.
-
variation
(move)¶ Gets a child node by either the move or the variation index.
-
has_variation
(move)¶ Checks if the given move appears as a variation.
-
promote_to_main
(move)¶ Promotes the given move to the main variation.
-
promote
(move)¶ Moves a variation one up in the list of variations.
-
demote
(move)¶ Moves a variation one down in the list of variations.
-
remove_variation
(move)¶ Removes a variation.
-
add_variation
(move, *, comment='', starting_comment='', nags=())¶ Creates a child node with the given attributes.
-
add_main_variation
(move, *, comment='')¶ Creates a child node with the given attributes and promotes it to the main variation.
-
mainline
()¶ Returns an iterator over the mainline starting after this node.
-
mainline_moves
()¶ Returns an iterator over the main moves after this node.
-
add_line
(moves, *, comment='', starting_comment='', nags=())¶ Creates a sequence of child nodes for the given list of moves. Adds comment and nags to the last node of the line and returns it.
-
accept
(visitor, *, _parent_board=None)¶ Traverses game nodes in PGN order using the given visitor. Starts with the move leading to this node. Returns the visitor result.
-
accept_subgame
(visitor)¶ Traverses headers and game nodes in PGN order, as if the game was starting after this node. Returns the visitor result.
-
Visitors¶
Visitors are an advanced concept for game tree traversal.
-
class
chess.pgn.
BaseVisitor
¶ Base class for visitors.
Use with
chess.pgn.Game.accept()
orchess.pgn.GameNode.accept()
orchess.pgn.read_game()
.The methods are called in PGN order.
-
begin_game
()¶ Called at the start of a game.
-
begin_headers
()¶ Called before visiting game headers.
-
visit_header
(tagname, tagvalue)¶ Called for each game header.
-
end_headers
()¶ Called after visiting game headers.
-
parse_san
(board, san)¶ When the visitor is used by a parser, this is called to parse a move in standard algebraic notation.
You can override the default implementation to work around specific quirks of your input format.
-
visit_move
(board, move)¶ Called for each move.
board is the board state before the move. The board state must be restored before the traversal continues.
-
visit_board
(board)¶ Called for the starting position of the game and after each move.
The board state must be restored before the traversal continues.
-
visit_comment
(comment)¶ Called for each comment.
-
visit_nag
(nag)¶ Called for each NAG.
-
begin_variation
()¶ Called at the start of a new variation. It is not called for the mainline of the game.
-
end_variation
()¶ Concludes a variation.
-
visit_result
(result)¶ Called at the end of a game with the value from the
Result
header.
-
end_game
()¶ Called at the end of a game.
-
result
()¶ Called to get the result of the visitor. Defaults to
True
.
-
handle_error
(error)¶ Called for encountered errors. Defaults to raising an exception.
-
The following visitors are readily available.
-
class
chess.pgn.
GameCreator
¶ Creates a game model. Default visitor for
read_game()
.-
handle_error
(error)¶ Populates
chess.pgn.Game.errors
with encountered errors and logs them.
-
-
class
chess.pgn.
HeaderCreator
¶ Collects headers into a dictionary.
-
class
chess.pgn.
BoardCreator
¶ Returns the final position of the game. The mainline of the game is on the move stack.
-
class
chess.pgn.
SkipVisitor
¶ Skips a game.
-
class
chess.pgn.
StringExporter
(*, columns=80, headers=True, comments=True, variations=True)¶ Allows exporting a game as a string.
>>> import chess.pgn >>> >>> game = chess.pgn.Game() >>> >>> exporter = chess.pgn.StringExporter(headers=True, variations=True, comments=True) >>> pgn_string = game.accept(exporter)
Only columns characters are written per line. If columns is
None
, then the entire movetext will be on a single line. This does not affect header tags and comments.There will be no newline characters at the end of the string.
-
class
chess.pgn.
FileExporter
(handle, *, columns=80, headers=True, comments=True, variations=True)¶ Acts like a
StringExporter
, but games are written directly into a text file.There will always be a blank line after each game. Handling encodings is up to the caller.
>>> import chess.pgn >>> >>> game = chess.pgn.Game() >>> >>> new_pgn = open("/dev/null", "w", encoding="utf-8") >>> exporter = chess.pgn.FileExporter(new_pgn) >>> game.accept(exporter)
NAGs¶
Numeric anotation glyphs describe moves and positions using standardized codes
that are understood by many chess programs. During PGN parsing, annotations
like !
, ?
, !!
, etc., are also converted to NAGs.
-
chess.pgn.
NAG_GOOD_MOVE
= 1¶ A good move. Can also be indicated by
!
in PGN notation.
-
chess.pgn.
NAG_MISTAKE
= 2¶ A mistake. Can also be indicated by
?
in PGN notation.
-
chess.pgn.
NAG_BRILLIANT_MOVE
= 3¶ A brilliant move. Can also be indicated by
!!
in PGN notation.
-
chess.pgn.
NAG_BLUNDER
= 4¶ A blunder. Can also be indicated by
??
in PGN notation.
-
chess.pgn.
NAG_SPECULATIVE_MOVE
= 5¶ A speculative move. Can also be indicated by
!?
in PGN notation.
-
chess.pgn.
NAG_DUBIOUS_MOVE
= 6¶ A dubious move. Can also be indicated by
?!
in PGN notation.
Skimming¶
These functions allow for quickly skimming games without fully parsing them.
-
chess.pgn.
read_headers
(handle)¶ Reads game headers from a PGN file opened in text mode.
Since actually parsing many games from a big file is relatively expensive, this is a better way to look only for specific games and then seek and parse them later.
This example scans for the first game with Kasparov as the white player.
>>> import chess.pgn >>> >>> pgn = open("data/pgn/kasparov-deep-blue-1997.pgn") >>> >>> kasparov_offsets = [] >>> >>> while True: ... offset = pgn.tell() ... ... headers = chess.pgn.read_headers(pgn) ... if headers is None: ... break ... ... if "Kasparov" in headers.get("White", "?"): ... kasparov_offsets.append(offset)
Then it can later be seeked an parsed.
>>> for offset in kasparov_offsets: ... pgn.seek(offset) ... chess.pgn.read_game(pgn) 0 <Game at ... ('Garry Kasparov' vs. 'Deep Blue (Computer)', 1997.??.??)> 1436 <Game at ... ('Garry Kasparov' vs. 'Deep Blue (Computer)', 1997.??.??)> 3067 <Game at ... ('Garry Kasparov' vs. 'Deep Blue (Computer)', 1997.??.??)>
-
chess.pgn.
skip_game
(handle)¶ Skip a game. Returns
True
if a game was found and skipped.
Polyglot opening book reading¶
-
chess.polyglot.
open_reader
(path)¶ Creates a reader for the file at the given path.
The following example opens a book to find all entries for the start position:
>>> import chess >>> import chess.polyglot >>> >>> board = chess.Board() >>> >>> with chess.polyglot.open_reader("data/polyglot/performance.bin") as reader: ... for entry in reader.find_all(board): ... print(entry.move(), entry.weight, entry.learn) e2e4 1 0 d2d4 1 0 c2c4 1 0
-
class
chess.polyglot.
Entry
¶ An entry from a Polyglot opening book.
-
key
¶ The Zobrist hash of the position.
-
raw_move
¶ The raw binary representation of the move. Use the
move()
method to extract a move object from this.
-
weight
¶ An integer value that can be used as the weight for this entry.
-
learn
¶ Another integer value that can be used for extra information.
-
-
class
chess.polyglot.
MemoryMappedReader
(filename)¶ Maps a Polyglot opening book to memory.
-
find_all
(board, *, minimum_weight=1, exclude_moves=())¶ Seeks a specific position and yields corresponding entries.
-
find
(board, *, minimum_weight=1, exclude_moves=())¶ Finds the main entry for the given position or Zobrist hash.
The main entry is the (first) entry with the highest weight.
By default, entries with weight
0
are excluded. This is a common way to delete entries from an opening book without compacting it. Pass minimum_weight0
to select all entries.Raises: IndexError
if no entries are found. Useget()
if you prefer to getNone
instead of an exception.
-
choice
(board, *, minimum_weight=1, exclude_moves=(), random=<module 'random' from '/home/docs/checkouts/readthedocs.org/user_builds/python-chess/envs/v0.24.2/lib/python3.5/random.py'>)¶ Uniformly selects a random entry for the given position.
Raises: IndexError
if no entries are found.
-
weighted_choice
(board, *, exclude_moves=(), random=<module 'random' from '/home/docs/checkouts/readthedocs.org/user_builds/python-chess/envs/v0.24.2/lib/python3.5/random.py'>)¶ Selects a random entry for the given position, distributed by the weights of the entries.
Raises: IndexError
if no entries are found.
-
close
()¶ Closes the reader.
-
-
chess.polyglot.
POLYGLOT_RANDOM_ARRAY
= [0x9D39247E33776D41, ..., 0xF8D626AAAF278509]¶ Array of 781 polyglot compatible pseudo random values for Zobrist hashing.
-
chess.polyglot.
zobrist_hash
(board, *, _hasher=<chess.polyglot.ZobristHasher object>)¶ Calculates the Polyglot Zobrist hash of the position.
A Zobrist hash is an XOR of pseudo-random values picked from an array. Which values are picked is decided by features of the position, such as piece positions, castling rights and en passant squares.
Gaviota endgame tablebase probing¶
Gaviota tablebases provide WDL (win/draw/loss) and DTM (depth to mate) information for all endgame positions with up to 5 pieces. Positions with castling rights are not included.
-
chess.gaviota.
open_tablebase
(directory, *, libgtb=None, LibraryLoader=<ctypes.LibraryLoader object>)¶ Opens a collection of tables for probing.
First native access via the shared library libgtb is tried. You can optionally provide a specific library name or a library loader. The shared library has global state and caches, so only one instance can be open at a time.
Second, pure Python probing code is tried.
-
class
chess.gaviota.
PythonTablebase
¶ Provides access to Gaviota tablebases using pure Python code.
-
add_directory
(directory)¶ Adds .gtb.cp4 tables from a directory. The relevant files are lazily opened when the tablebase is actually probed.
-
probe_dtm
(board)¶ Probes for depth to mate information.
The absolute value is the number of half-moves until forced mate (or
0
in drawn positions). The value is positive if the side to move is winning, otherwise it is negative.In the example position white to move will get mated in 10 half-moves:
>>> import chess >>> import chess.gaviota >>> >>> with chess.gaviota.open_tablebase("data/gaviota") as tablebase: ... board = chess.Board("8/8/8/8/8/8/8/K2kr3 w - - 0 1") ... print(tablebase.probe_dtm(board)) ... -10
Raises: KeyError
(or specificallychess.gaviota.MissingTableError
) if the probe fails. Useget_dtm()
if you prefer to getNone
instead of an exception.Note that probing a corrupted table file is undefined behavior.
-
probe_wdl
(board)¶ Probes for win/draw/loss-information.
Returns
1
if the side to move is winning,0
if it is a draw, and-1
if the side to move is losing.>>> import chess >>> import chess.gaviota >>> >>> with chess.gaviota.open_tablebase("data/gaviota") as tablebase: ... board = chess.Board("8/4k3/8/B7/8/8/8/4K3 w - - 0 1") ... print(tablebase.probe_wdl(board)) ... 0
Raises: KeyError
(or specificallychess.gaviota.MissingTableError
) if the probe fails. Useget_wdl()
if you prefer to getNone
instead of an exception.Note that probing a corrupted table file is undefined behavior.
-
close
()¶ Closes all loaded tables.
-
libgtb¶
For faster access you can build and install a shared library. Otherwise the pure Python probing code is used.
git clone https://github.com/michiguel/Gaviota-Tablebases.git
cd Gaviota-Tablebases
make
sudo make install
-
chess.gaviota.
open_tablebase_native
(directory, *, libgtb=None, LibraryLoader=<ctypes.LibraryLoader object>)¶ Opens a collection of tables for probing using libgtb.
In most cases
open_tablebase()
should be used. Use this function only if you do not want to downgrade to pure Python tablebase probing.Raises: RuntimeError
orOSError
when libgtb can not be used.
-
class
chess.gaviota.
NativeTablebase
(libgtb)¶ Provides access to Gaviota tablebases via the shared library libgtb. Has the same interface as
PythonTablebase
.
Syzygy endgame tablebase probing¶
Syzygy tablebases provide WDL (win/draw/loss) and DTZ (distance to zero) information for all endgame positions with up to 6 (and experimentally 7) pieces. Positions with castling rights are not included.
-
chess.syzygy.
open_tablebase
(directory, *, load_wdl=True, load_dtz=True, max_fds=128, VariantBoard=<class 'chess.Board'>)¶ Opens a collection of tables for probing. See
Tablebase
.Note
Generally probing requires tablebase files for the specific material composition, as well as tablebase files with less pieces. This is important because 6-piece and 5-piece files are often distributed seperately, but are both required for 6-piece positions. Use
add_directory()
to load tables from additional directories.
-
class
chess.syzygy.
Tablebase
(*, max_fds=128, VariantBoard=<class 'chess.Board'>)¶ Manages a collection of tablebase files for probing.
If max_fds is not
None
, will at most use max_fds open file descriptors at any given time. The least recently used tables are closed, if nescessary.-
add_directory
(directory, *, load_wdl=True, load_dtz=True)¶ Adds tables from a directory.
By default all available tables with the correct file names (e.g. WDL files like
KQvKN.rtbw
and DTZ files likeKRBvK.rtbz
) are added.The relevant files are lazily opened when the tablebase is actually probed.
Returns the number of table files that were found.
-
probe_wdl
(board)¶ Probes WDL tables for win/draw/loss-information.
Probing is thread-safe when done with different board objects and if board objects are not modified during probing.
Returns
2
if the side to move is winning,0
if the position is a draw and-2
if the side to move is losing.Returns
1
in case of a cursed win and-1
in case of a blessed loss. Mate can be forced but the position can be drawn due to the fifty-move rule.>>> import chess >>> import chess.syzygy >>> >>> with chess.syzygy.open_tablebase("data/syzygy/regular") as tablebase: ... board = chess.Board("8/2K5/4B3/3N4/8/8/4k3/8 b - - 0 1") ... print(tablebase.probe_wdl(board)) ... -2
Raises: KeyError
(or specificallychess.syzygy.MissingTableError
) if the position could not be found in the tablebase. Useget_wdl()
if you prefer to getNone
instead of an exception.Note that probing corrupted table files is undefined behavior.
-
probe_dtz
(board)¶ Probes DTZ tables for distance to zero information.
Both DTZ and WDL tables are required in order to probe for DTZ.
Returns a positive value if the side to move is winning,
0
if the position is a draw and a negative value if the side to move is losing. More precisely:WDL DTZ -2 -100 <= n <= -1 Unconditional loss (assuming 50-move counter is zero), where a zeroing move can be forced in -n plies. -1 n < -100 Loss, but draw under the 50-move rule. A zeroing move can be forced in -n plies or -n - 100 plies (if a later phase is responsible for the blessed loss). 0 0 Draw. 1 100 < n Win, but draw under the 50-move rule. A zeroing move can be forced in n plies or n - 100 plies (if a later phase is responsible for the cursed win). 2 1 <= n <= 100 Unconditional win (assuming 50-move counter is zero), where a zeroing move can be forced in n plies. The return value can be off by one: a return value -n can mean a losing zeroing move in in n + 1 plies and a return value +n can mean a winning zeroing move in n + 1 plies. This is guaranteed not to happen for positions exactly on the edge of the 50-move rule, so that (with some care) this never impacts the result of practical play.
Minmaxing the DTZ values guarantees winning a won position (and drawing a drawn position), because it makes progress keeping the win in hand. However the lines are not always the most straightforward ways to win. Engines like Stockfish calculate themselves, checking with DTZ, but only play according to DTZ if they can not manage on their own.
>>> import chess >>> import chess.syzygy >>> >>> with chess.syzygy.open_tablebase("data/syzygy/regular") as tablebase: ... board = chess.Board("8/2K5/4B3/3N4/8/8/4k3/8 b - - 0 1") ... print(tablebase.probe_dtz(board)) ... -53
Probing is thread-safe when done with different board objects and if board objects are not modified during probing.
Raises: KeyError
(or specificallychess.syzygy.MissingTableError
) if the position could not be found in the tablebase. Useget_dtz()
if you prefer to getNone
instead of an exception.Note that probing corrupted table files is undefined behavior.
-
close
()¶ Closes all loaded tables.
-
UCI engine communication¶
The Universal Chess Interface is a protocol for communicating with engines.
-
chess.uci.
popen_engine
(command, *, engine_cls=<class 'chess.uci.Engine'>, setpgrp=False, **kwargs)¶ Opens a local chess engine process.
No initialization commands are sent, so do not forget to send the mandatory uci command.
>>> engine = chess.uci.popen_engine("/usr/bin/stockfish") >>> engine.uci() >>> engine.name 'Stockfish 8 64 POPCNT' >>> engine.author 'T. Romstad, M. Costalba, J. Kiiski, G. Linscott'
Parameters: - command –
- engine_cls –
- setpgrp – Open the engine process in a new process group. This will
stop signals (such as keyboard interrupts) from propagating from the
parent process. Defaults to
False
.
-
chess.uci.
spur_spawn_engine
(shell, command, *, engine_cls=<class 'chess.uci.Engine'>)¶ Spawns a remote engine using a Spur shell.
>>> import spur >>> >>> shell = spur.SshShell(hostname="localhost", username="username", password="pw") >>> engine = chess.uci.spur_spawn_engine(shell, ["/usr/bin/stockfish"]) >>> engine.uci()
-
class
chess.uci.
Engine
(*, Executor=<class 'concurrent.futures.thread.ThreadPoolExecutor'>)¶ -
process
¶ The underlying operating system process.
-
name
¶ The name of the engine. Conforming engines should send this as id name when they receive the initial uci command.
The author of the engine. Conforming engines should send this as id author after the initial uci command.
-
options
¶ A case-insensitive dictionary of Options. The engine should send available options when it receives the initial uci command.
-
uciok
¶ threading.Event()
that will be set as soon as uciok was received. By thenname
,author
andoptions
should be available.
-
return_code
¶ The return code of the operating system process.
-
terminated
¶ threading.Event()
that will be set as soon as the underyling operating system process is terminated and thereturn_code
is available.
-
terminate
(*, async_callback=None)¶ Terminate the engine.
This is not an UCI command. It instead tries to terminate the engine on operating system level, like sending SIGTERM on Unix systems. If possible, first try the quit command.
Returns: The return code of the engine process (or a Future).
-
kill
(*, async_callback=None)¶ Kill the engine.
Forcefully kill the engine process, like by sending SIGKILL.
Returns: The return code of the engine process (or a Future).
-
is_alive
()¶ Poll the engine process to check if it is alive.
-
UCI commands¶
-
class
chess.uci.
Engine
(*, Executor=<class 'concurrent.futures.thread.ThreadPoolExecutor'>) -
uci
(*, async_callback=None)¶ Tells the engine to use the UCI interface.
This is mandatory before any other command. A conforming engine will send its name, authors and available options.
Returns: Nothing
-
debug
(on, *, async_callback=None)¶ Switch the debug mode on or off.
In debug mode, the engine should send additional information to the GUI to help with the debugging. Usually, this mode is off by default.
Parameters: on – bool Returns: Nothing
-
isready
(*, async_callback=None)¶ Command used to synchronize with the engine.
The engine will respond as soon as it has handled all other queued commands.
Returns: Nothing
-
setoption
(options, *, async_callback=None)¶ Set values for the engine’s available options.
Parameters: options – A dictionary with option names as keys. Returns: Nothing
-
ucinewgame
(*, async_callback=None)¶ Tell the engine that the next search will be from a different game.
This can be a new game the engine should play or if the engine should analyse a position from a different game. Using this command is recommended, but not required.
Returns: Nothing
-
position
(board, *, async_callback=None)¶ Set up a given position.
Rather than sending just the final FEN, the initial FEN and all moves leading up to the position will be sent. This will allow the engine to use the move history (for example to detect repetitions).
If the position is from a new game, it is recommended to use the ucinewgame command before the position command.
Parameters: board – A chess.Board. Returns: Nothing Raises: EngineStateException
if the engine is still calculating.
-
go
(*, searchmoves=None, ponder=False, wtime=None, btime=None, winc=None, binc=None, movestogo=None, depth=None, nodes=None, mate=None, movetime=None, infinite=False, async_callback=None)¶ Start calculating on the current position.
All parameters are optional, but there should be at least one of depth, nodes, mate, infinite or some time control settings, so that the engine knows how long to calculate.
Note that when using infinite or ponder, the engine will not stop until it is told to.
Parameters: - searchmoves – Restrict search to moves in this list.
- ponder – Bool to enable pondering mode. The engine will not stop pondering in the background until a stop command is received.
- wtime – Integer of milliseconds White has left on the clock.
- btime – Integer of milliseconds Black has left on the clock.
- winc – Integer of white Fisher increment.
- binc – Integer of black Fisher increment.
- movestogo – Number of moves to the next time control. If this is not set, but wtime or btime are, then it is sudden death.
- depth – Search depth ply only.
- nodes – Search so many nodes only.
- mate – Search for a mate in mate moves.
- movetime – Integer. Search exactly movetime milliseconds.
- infinite – Search in the background until a stop command is received.
Returns: A tuple of two elements. The first is the best move according to the engine. The second is the ponder move. This is the reply as sent by the engine. Either of the elements may be
None
.Raises: EngineStateException
if the engine is already calculating.
-
stop
(*, async_callback=None)¶ Stop calculating as soon as possible.
Returns: Nothing.
-
ponderhit
(*, async_callback=None)¶ May be sent if the expected ponder move has been played.
The engine should continue searching, but should switch from pondering to normal search.
Returns: Nothing. Raises: EngineStateException
if the engine is not currently searching in ponder mode.
-
quit
(*, async_callback=None)¶ Quit the engine as soon as possible.
Returns: The return code of the engine process.
-
EngineTerminatedException
is raised if the engine process is
no longer alive.
Asynchronous communication¶
By default, all operations are executed synchronously and their result is returned. For example
>>> import chess.uci
>>>
>>> engine = chess.uci.popen_engine("stockfish")
>>>
>>> engine.go(movetime=2000)
BestMove(bestmove=Move.from_uci('e2e4'), ponder=None)
will take about 2000 milliseconds. All UCI commands have an optional async_callback argument. They will then immediately return a Future and continue.
>>> command = engine.go(movetime=2000, async_callback=True)
>>> command.done()
False
>>> command.result() # Synchronously wait for the command to finish
BestMove(bestmove=Move.from_uci('e2e4'), ponder=None)
>>> command.done()
True
Instead of just passing async_callback=True, a callback function may be passed. It will be invoked possibly on a different thread as soon as the command is completed. It takes the command future as a single argument.
>>> def on_go_finished(command):
... # Will likely be executed on a different thread.
... bestmove, ponder = command.result()
...
>>> command = engine.go(movetime=2000, async_callback=on_go_finished)
Info handler¶
-
class
chess.uci.
Score
¶ A cp (centipawns) or mate score sent by an UCI engine.
-
cp
¶ Evaluation in centipawns or
None
.
-
mate
¶ Mate in x or
None
. Negative number if the engine thinks it is going to be mated.
-
-
class
chess.uci.
InfoHandler
¶ Chess engines may send information about their calculations with the info command. An
InfoHandler
instance can be used to aggregate or react to this information.>>> import chess.uci >>> >>> engine = chess.uci.popen_engine("stockfish") >>> >>> # Register a standard info handler. >>> info_handler = chess.uci.InfoHandler() >>> engine.info_handlers.append(info_handler) >>> >>> # Start a search. >>> engine.position(chess.Board()) >>> engine.go(movetime=1000) BestMove(bestmove=Move.from_uci('e2e4'), ponder=Move.from_uci('e7e6')) >>> >>> # Retrieve the score of the mainline (PV 1) after search is completed. >>> # Note that the score is relative to the side to move. >>> info_handler.info["score"][1] Score(cp=34, mate=None)
See
info
for a way to access this dictionary in a thread-safe way during search.If you want to be notified whenever new information is available, you would usually subclass the
InfoHandler
class:>>> class MyHandler(chess.uci.InfoHandler): ... def post_info(self): ... # Called whenever a complete info line has been processed. ... print(self.info) ... super().post_info() # Release the lock
-
info
¶ The default implementation stores all received information in this dictionary. To get a consistent snapshot, use the object as if it were a
threading.Lock()
.>>> # Start thinking. >>> engine.go(infinite=True, async_callback=True)
>>> # Wait a moment, then access a consistent snapshot. >>> time.sleep(3) >>> with info_handler: ... if 1 in info_handler.info["score"]: ... print("Score: ", info_handler.info["score"][1].cp) ... print("Mate: ", info_handler.info["score"][1].mate) Score: 34 Mate: None
-
depth
(x)¶ Receives the search depth in plies.
-
seldepth
(x)¶ Receives the selective search depth in plies.
-
time
(x)¶ Receives a new time searched in milliseconds.
-
nodes
(x)¶ Receives the number of nodes searched.
-
pv
(moves)¶ Receives the principal variation as a list of moves.
In MultiPV mode, this is related to the most recent multipv number sent by the engine.
-
multipv
(num)¶ Receives a new multipv number, starting at 1.
If multipv occurs in an info line, this is guaranteed to be called before score or pv.
-
score
(cp, mate, lowerbound, upperbound)¶ Receives a new evaluation in cp (centipawns) or a mate score.
cp may be
None
if no score in centipawns is available.mate may be
None
if no forced mate has been found. A negative number means the engine thinks it will get mated.lowerbound and upperbound are usually
False
. IfTrue
, the sent score is just a lowerbound or upperbound.In MultiPV mode, this is related to the most recent multipv number sent by the engine.
-
currmove
(move)¶ Receives a move the engine is currently thinking about.
The move comes directly from the engine, so the castling move representation depends on the UCI_Chess960 option of the engine.
-
currmovenumber
(x)¶ Receives a new current move number.
-
hashfull
(x)¶ Receives new information about the hash table.
The hash table is x permill full.
-
nps
(x)¶ Receives a new nodes per second (nps) statistic.
-
tbhits
(x)¶ Receives a new information about the number of tablebase hits.
-
cpuload
(x)¶ Receives a new cpuload information in permill.
-
string
(string)¶ Receives a string the engine wants to display.
-
refutation
(move, refuted_by)¶ Receives a new refutation of a move.
refuted_by may be a list of moves representing the mainline of the refutation or
None
if no refutation has been found.Engines should only send refutations if the UCI_ShowRefutations option has been enabled.
-
currline
(cpunr, moves)¶ Receives a new snapshot of a line that a specific CPU is calculating.
cpunr is an integer representing a specific CPU and moves is a list of moves.
-
ebf
(ebf)¶ Receives the effective branching factor.
-
pre_info
(line)¶ Receives new info lines before they are processed.
When subclassing, remember to call this method on the parent class to keep the locking intact.
-
post_info
()¶ Processing of a new info line has been finished.
When subclassing, remember to call this method on the parent class to keep the locking intact.
-
on_bestmove
(bestmove, ponder)¶ Receives a new bestmove and a new ponder move.
-
on_go
()¶ Notified when a go command is beeing sent.
Since information about the previous search is invalidated, the dictionary with the current information will be cleared.
-
Options¶
-
class
chess.uci.
Option
¶ Information about an available option for an UCI engine.
-
name
¶ The name of the option.
-
type
¶ The type of the option.
Officially documented types are
check
for a boolean value,spin
for an integer value between a minimum and a maximum,combo
for an enumeration of predefined string values (one of which can be selected),button
for an action andstring
for a text field.
-
default
¶ The default value of the option.
There is no need to send a setoption command with the defaut value.
-
min
¶ The minimum integer value of a spin option.
-
max
¶ The maximum integer value of a spin option.
-
var
¶ A list of allows string values for a combo option.
-
SVG rendering¶
The chess.svg
module renders SVG Tiny images (mostly for IPython/Jupyter
Notebook integration). The piece images by
Colin M.L. Burnett are triple
licensed under the GFDL, BSD and GPL.
-
chess.svg.
piece
(piece, size=None)¶ Renders the given
chess.Piece
as an SVG image.>>> import chess >>> import chess.svg >>> >>> chess.svg.piece(chess.Piece.from_symbol("R"))
-
chess.svg.
board
(board=None, *, squares=None, flipped=False, coordinates=True, lastmove=None, check=None, arrows=(), size=None, style=None)¶ Renders a board with pieces and/or selected squares as an SVG image.
Parameters: - board – A
chess.BaseBoard
for a chessboard with pieces orNone
(the default) for a chessboard without pieces. - squares – A
chess.SquareSet
with selected squares. - flipped – Pass
True
to flip the board. - coordinates – Pass
False
to disable coordinates in the margin. - lastmove – A
chess.Move
to be highlighted. - check – A square to be marked as check.
- arrows – A list of
Arrow
objects like[chess.svg.Arrow(chess.E2, chess.E4)]
or a list of tuples like[(chess.E2, chess.E4)]
. An arrow from a square pointing to the same square is drawn as a circle, like[(chess.E2, chess.E2)]
. - size – The size of the image in pixels (e.g.,
400
for a 400 by 400 board) orNone
(the default) for no size limit. - style – A CSS stylesheet to include in the SVG image.
>>> import chess >>> import chess.svg >>> >>> board = chess.Board("8/8/8/8/4N3/8/8/8 w - - 0 1") >>> squares = board.attacks(chess.E4) >>> chess.svg.board(board=board, squares=squares)
- board – A
Variants¶
python-chess supports several chess variants.
>>> import chess.variant
>>>
>>> board = chess.variant.GiveawayBoard()
>>> # General information about the variants
>>> type(board).uci_variant
'giveaway'
>>> type(board).starting_fen
'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1'
See chess.Board.is_variant_end()
, is_variant_win()
is_variant_draw()
is_variant_loss()
for special variant end conditions and results.
Variant | Board class | UCI | Syzygy |
---|---|---|---|
Standard | chess.Board |
chess | .rtbw, .rtbz |
Suicide | chess.variant.SuicideBoard |
suicide | .stbw, .stbz |
Giveaway | chess.variant.GiveawayBoard |
giveaway | .gtbw, .gtbz |
Atomic | chess.variant.AtomicBoard |
atomic | .atbw, .atbz |
King of the Hill | chess.variant.KingOfTheHillBoard |
kingofthehill | |
Racing Kings | chess.variant.RacingKingsBoard |
racingkings | |
Horde | chess.variant.HordeBoard |
horde | |
Three-check | chess.variant.ThreeCheckBoard |
3check | |
Crazyhouse | chess.variant.CrazyhouseBoard |
crazyhouse |
-
chess.variant.
find_variant
(name)¶ Looks for a variant board class by variant name.
Chess960¶
Chess960 is orthogonal to all other variants.
>>> chess.Board(chess960=True)
Board('rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1', chess960=True)
See chess.BaseBoard.set_chess960_pos()
,
chess960_pos()
, and
from_chess960_pos()
for dealing with Chess960 starting
positions.
UCI¶
Multi-Variant Stockfish and other engines have an UCI_Variant
option.
This is automatically managed.
>>> import chess.uci
>>> import chess.variant
>>>
>>> engine = chess.uci.popen_engine("stockfish")
>>> engine.uci()
>>>
>>> board = chess.variant.RacingKingsBoard()
>>> engine.position(board)
Syzygy¶
Syzygy tablebases are available for suicide, giveaway and atomic chess.
>>> import chess.syzygy
>>> import chess.variant
>>>
>>> tables = chess.syzygy.open_tablebase("data/syzygy", VariantBoard=chess.variant.AtomicBoard)
Changelog for python-chess¶
New in v0.24.2¶
Bugfixes:
- CrazyhouseBoard.root() and ThreeCheckBoard.root() were not returning the correct pockets and number of remaining checks, respectively. Thanks @gbtami.
- chess.pgn.skip_game() now correctly skips PGN comments that contain line-breaks and PGN header tag notation.
Changes:
- Renamed chess.pgn.GameModelCreator to GameCreator. Alias kept in place and will be removed in a future release.
- Renamed chess.engine to chess._engine. Use re-exports from chess.uci or chess.xboard.
- Renamed Board.stack to Board._stack. Do not use this directly.
- Improved memory usage: Board.legal_moves and Board.pseudo_legal_moves no longer create reference cycles. PGN visitors can manage headers themselves.
- Removed previously deprecated items.
Features:
- Added chess.pgn.BaseVisitor.visit_board() and chess.pgn.BoardCreator.
New in v0.24.1, v0.23.11¶
Bugfixes:
- Fix chess.Board.set_epd() and chess.Board.from_epd() with semicolon in string operand. Thanks @jdart1.
- chess.pgn.GameNode.uci() was always raising an exception. Also included in v0.24.0.
New in v0.24.0¶
This release drops support for Python 2. The 0.23.x branch will be maintained for one more month.
Changes:
- Require Python 3.4. Thanks @hugovk.
- No longer using extra pip features: pip install python-chess[engine,gaviota] is now pip install python-chess.
- Various keyword arguments can now be used as keyword arguments only.
- chess.pgn.GameNode.accept() now also visits the move leading to that node.
- chess.pgn.GameModelCreator now requires that begin_game() be called.
- chess.pgn.scan_headers() and chess.pgn.scan_offsets() have been removed. Instead the new functions chess.pgn.read_headers() and chess.pgn.skip_game() can be used for a similar purpose.
- chess.syzygy: Invalid magic headers now raise IOError. Previously they were only checked in an assertion. type(board).{tbw_magic,tbz_magic,pawnless_tbw_magic,pawnless_tbz_magic} are now byte literals.
- board.status() constants (STATUS_) are now typed using enum.IntFlag. Values remain unchanged.
- chess.svg.Arrow is no longer a namedtuple.
- chess.PIECE_SYMBOLS[0] and chess.PIECE_NAMES[0] are now None instead of empty strings.
- Performance optimizations:
- chess.pgn.Game.from_board(),
- chess.square_name()
- Replace collections.deque with lists almost everywhere.
- Renamed symbols (aliases will be removed in the next release):
- chess.BB_VOID -> BB_EMPTY
- chess.bswap() -> flip_vertical()
- chess.pgn.GameNode.main_line() -> mainline_moves()
- chess.pgn.GameNode.is_main_line() -> is_mainline()
- chess.variant.BB_HILL -> chess.BB_CENTER
- chess.syzygy.open_tablebases() -> open_tablebase()
- chess.syzygy.Tablebases -> Tablebase
- chess.syzygy.Tablebase.open_directory() -> add_directory()
- chess.gaviota.open_tablebases() -> open_tablebase()
- chess.gaviota.open_tablebases_native() -> open_tablebase_native()
- chess.gaviota.NativeTablebases -> NativeTablebase
- chess.gaviota.PythonTablebases -> PythonTablebase
- chess.gaviota.NativeTablebase.open_directory() -> add_directory()
- chess.gaviota.PythonTablebase.open_directory() -> add_directory()
Bugfixes:
- The PGN parser now gives the visitor a chance to handle unknown chess variants and continue parsing.
- chess.pgn.GameNode.uci() was always raising an exception.
New features:
- chess.SquareSet now extends collections.abc.MutableSet and can be initialized from iterables.
- board.apply_transform(f) and board.transform(f) can apply bitboard transformations to a position. Examples: chess.flip_{vertical,horizontal,diagonal,anti_diagonal}.
- chess.pgn.GameNode.mainline() iterates over nodes of the mainline. Can also be used with reversed(). Reversal is now also supported for chess.pgn.GameNode.mainline_moves().
- chess.svg.Arrow(tail, head, color=”#888”) gained an optional color argument.
- chess.pgn.BaseVisitor.parse_san(board, san) is used by parsers and can be overwritten to deal with non-standard input formats.
- chess.pgn: Visitors can advise the parser to skip games or variations by returning the special value chess.pgn.SKIP from begin_game(), end_headers() or begin_variation(). This is only a hint. The corresponding end_game() or end_variation() will still be called.
- Added chess.svg.MARGIN.
New in v0.23.10¶
Bugfixes:
- chess.SquareSet now correctly handles negative masks. Thanks @hasnul.
- chess.pgn now accepts [Variant “chess 960”] (with the space).
New in v0.23.9¶
Changes:
- Updated Board.is_fivefold_repetition(). FIDE rules have changed and the repetition no longer needs to occur on consecutive alternating moves. Thanks @LegionMammal978.
New in v0.23.8¶
Bugfixes:
- chess.syzygy: Correctly initialize wide DTZ map for experimental 7 piece table KRBBPvKQ.
New in v0.23.7¶
Bugfixes:
- Fixed ThreeCheckBoard.mirror() and CrazyhouseBoard.mirror(), which were previously resetting remaining checks and pockets respectively. Thanks @QueensGambit.
Changes:
- Board.move_stack is now guaranteed to be UCI compatible with respect to the representation of castling moves and board.chess960.
- Drop support for Python 3.3, which is long past end of life.
- chess.uci: The position command now manages UCI_Chess960 and UCI_Variant automatically.
- chess.uci: The position command will now always send the entire history of moves from the root position.
- Various coding style fixes and improvements. Thanks @hugovk.
New features:
- Added Board.root().
New in v0.23.6¶
Bugfixes:
- Gaviota: Fix Python based Gaviota tablebase probing when there are multiple en passant captures. Thanks @bjoernholzhauer.
- Syzygy: Fix DTZ for some mate in 1 positions. Similarly to the fix from v0.23.1 this is mostly cosmetic.
- Syzygy: Fix DTZ off-by-one in some 6 piece antichess positions with moves that threaten to force a capture. This is mostly cosmetic.
Changes:
- Let uci.Engine.position() send history of at least 8 moves if available. Previously it sent only moves that were relevant for repetition detection. This is mostly useful for Lc0. Once performance issues are solved, a future version will always send the entire history. Thanks @SashaMN and @Mk-Chan.
- Various documentation fixes and improvements.
New features:
- Added polyglot.MemoryMappedReader.get(board, default=None).
New in v0.23.5¶
Bugfixes:
- Atomic chess: KNvKN is not insufficient material.
- Crazyhouse: Detect insufficient material. This can not happen unless the game was started with insufficient material.
Changes:
- Better error messages when parsing info from UCI engine fails.
- Better error message for b.set_board_fen(b.fen()).
New in v0.23.4¶
New features:
- XBoard: Support pondering. Thanks Manik Charan.
- UCI: Support unofficial info ebf.
Bugfixes:
- Implement 16 bit DTZ mapping, which is required for some of the longest 7 piece endgames.
New in v0.23.2¶
Bugfixes:
- XBoard: Handle multiple features and features with spaces. Thanks gbtami.
- XBoard: Ignore debug output prefixed with #. Thanks Dan Ravensloft and Manik Charan.
New in v0.23.1¶
Bugfixes:
- Fix DTZ in case of mate in 1. This is a cosmetic fix, as the previous behavior was only off by one (which is allowed by design).
New in v0.23.0¶
New features:
- Experimental support for 7 piece Syzygy tablebases.
Changes:
- chess.syzygy.filenames() was renamed to tablenames() and gained an optional piece_count=6 argument.
- chess.syzygy.normalize_filename() was renamed to normalize_tablename().
- The undocumented constructors of chess.syzygy.WdlTable and chess.syzygy.DtzTable have been changed.
New in v0.22.2¶
Bugfixes:
- In standard chess promoted pieces were incorrectly considered as distinguishable from normal pieces with regard to position equality and threefold repetition. Thanks to kn-sq-tb for reporting.
Changes:
- The PGN game.headers are now a custom mutable mapping that validates the validity of tag names.
- Basic attack and pin methods moved to BaseBoard.
- Documentation fixes and improvements.
New features:
- Added Board.lan() for long algebraic notation.
New in v0.22.1¶
New features:
- Added Board.mirror(), SquareSet.mirror() and bswap().
- Added chess.pgn.GameNode.accept_subgame().
- XBoard: Added resign, analyze, exit, name, rating, computer, egtpath, pause, resume. Completed option parsing.
Changes:
- chess.pgn: Accept FICS wilds without warning.
- XBoard: Inform engine about game results.
Bugfixes:
- chess.pgn: Allow games without movetext.
- XBoard: Fixed draw handling.
New in v0.22.0¶
Changes:
- len(board.legal_moves) replaced by board.legal_moves.count(). Previously list(board.legal_moves) was generating moves twice, resulting in a considerable slowdown. Thanks to Martin C. Doege for reporting.
- Dropped Python 2.6 support.
- XBoard: offer_draw renamed to draw.
New features:
- XBoard: Added DrawHandler.
New in v0.21.2¶
Changes:
- chess.svg is now fully SVG Tiny 1.2 compatible. Removed chess.svg.DEFAULT_STYLE which would from now on be always empty.
New in v0.21.1¶
Bugfixes:
- Board.set_piece_at() no longer shadows optional promoted argument from BaseBoard.
- Fixed ThreeCheckBoard.is_irreversible() and ThreeCheckBoard._transposition_key().
New features:
- Added Game.without_tag_roster(). chess.pgn.StringExporter() can now handle games without any headers.
- XBoard: white, black, random, nps, otim, undo, remove. Thanks to Manik Charan.
Changes:
- Documentation fixes and tweaks by Boštjan Mejak.
- Changed unicode character for empty squares in Board.unicode().
New in v0.21.0¶
Release yanked.
New in v0.20.1¶
Bugfixes:
- Fix arrow positioning on SVG boards.
- Documentation fixes and improvements, making most doctests runnable.
New in v0.20.0¶
Bugfixes:
- Some XBoard commands were not returning futures.
- Support semicolon comments in PGNs.
Changes:
- Changed FEN and EPD formatting options. It is now possible to include en passant squares in FEN and X-FEN style, or to include only strictly relevant en passant squares.
- Relax en passant square validation in Board.set_fen().
- Ensure is_en_passant(), is_capture(), is_zeroing() and is_irreversible() strictly return bools.
- Accept Z0 as a null move in PGNs.
New features:
- XBoard: Add memory, core, stop and movenow commands. Abstract post/nopost. Initial FeatureMap support. Support usermove.
- Added Board.has_pseudo_legal_en_passant().
- Added Board.piece_map().
- Added SquareSet.carry_rippler().
- Factored out some (unstable) low level APIs: BB_CORNERS, _carry_rippler(), _edges().
New in v0.19.0¶
New features:
- Experimental XBoard engine support. Thanks to Manik Charan and Cash Costello. Expect breaking changes in future releases.
- Added an undocumented chess.polyglot.ZobristHasher to make Zobrist hashing easier to extend.
Bugfixes:
- Merely pseudo-legal en passant does no longer count for repetitions.
- Fixed repetition detection in Three-Check and Crazyhouse. (Previously check counters and pockets were ignored.)
- Checking moves in Three-Check are now considered as irreversible by ThreeCheckBoard.is_irreversible().
- chess.Move.from_uci(“”) was raising IndexError instead of ValueError. Thanks Jonny Balls.
Changes:
- chess.syzygy.Tablebases constructor no longer supports directly opening a directory. Use chess.syzygy.open_tablebases().
- chess.gaviota.PythonTablebases and NativeTablebases constructors no longer support directly opening a directory. Use chess.gaviota.open_tablebases().
- chess.Board instances are now compared by the position they represent, not by exact match of the internal data structures (or even move history).
- Relaxed castling right validation in Chess960: Kings/rooks of opposing sites are no longer required to be on the same file.
- Removed misnamed Piece.__unicode__() and BaseBoard.__unicode__(). Use Piece.unicode_symbol() and BaseBoard.unicode() instead.
- Changed chess.SquareSet.__repr__().
- Support [Variant “normal”] in PGNs.
- pip install python-chess[engine] instead of python-chess[uci] (since the extra dependencies are required for both UCI and XBoard engines).
- Mixed documentation fixes and improvements.
New in v0.18.4¶
Changes:
- Support [Variant “fischerandom”] in PGNs for Cutechess compability. Thanks to Steve Maughan for reporting.
New in v0.18.2¶
Bugfixes:
- Fixed castling in atomic chess when there is a rank attack.
- The halfmove clock in Crazyhouse is no longer incremented unconditionally. CrazyhouseBoard.is_zeroing(move) now considers pawn moves and captures as zeroing. Added Board.is_irreversible(move) that can be used instead.
- Fixed an inconsistency where the chess.pgn tokenizer accepts long algebraic notation but Board.parse_san() did not.
Changes:
- Added more NAG constants in chess.pgn.
New in v0.18.1¶
Bugfixes:
- Crazyhouse drops were accepted as pseudo legal (and legal) even if the respective piece was not in the pocket.
- CrazyhouseBoard.pop() was failing to undo en passant moves.
- CrazyhouseBoard.pop() was always returning None.
- Move.__copy__() was failing to copy Crazyhouse drops.
- Fix ~ order (marker for promoted pieces) in FENs.
- Promoted pieces in Crazyhouse were not communicated with UCI engines.
Changes:
- ThreeCheckBoard.uci_variant changed from threecheck to 3check.
New in v0.18.0¶
Bugfixes:
- Fixed Board.parse_uci() for crazyhouse drops. Thanks to Ryan Delaney.
- Fixed AtomicBoard.is_insufficient_material().
- Fixed signature of SuicideBoard.was_into_check().
- Explicitly close input and output streams when a chess.uci.PopenProcess terminates.
- The documentation of Board.attackers() was wrongly stating that en passant capturable pawns are considered attacked.
Changes:
- chess.SquareSet is no longer hashable (since it is mutable).
- Removed functions and constants deprecated in v0.17.0.
- Dropped gmpy2 and gmpy as optional dependencies. They were no longer improving performance.
- Various tweaks and optimizations for 5% improvement in PGN parsing and perft speed. (Signature of _is_safe and _ep_skewered changed).
- Rewritten chess.svg.board() using xml.etree. No longer supports pre and post. Use an XML parser if you need to modify the SVG. Now only inserts actually used piece defintions.
- Untangled UCI process and engine instanciation, changing signatures of constructors and allowing arbitrary arguments to subprocess.Popen.
- Coding style and documentation improvements.
New features:
- chess.svg.board() now supports arrows. Thanks to @rheber for implementing this feature.
- Let chess.uci.PopenEngine consistently handle Ctrl+C across platforms and Python versions. chess.uci.popen_engine() now supports a setpgrp keyword argument to start the engine process in a new process group. Thanks to @dubiousjim.
- Added board.king(color) to find the (royal) king of a given side.
- SVGs now have viewBox and chess.svg.board(size=None) supports and defaults to None (i.e. scaling to the size of the container).
New in v0.17.0¶
Changes:
- Rewritten move generator, various performance tweaks, code simplications (500 lines removed) amounting to doubled PGN parsing and perft speed.
- Removed board.generate_evasions() and board.generate_non_evasions().
- Removed board.transpositions. Transpositions are now counted on demand.
- file_index(), rank_index(), and pop_count() have been renamed to square_file(), square_rank() and popcount() respectively. Aliases will be removed in some future release.
- STATUS_ILLEGAL_CHECK has been renamed to STATUS_RACE_CHECK. The alias will be removed in a future release.
- Removed DIAG_ATTACKS_NE, DIAG_ATTACKS_NW, RANK_ATTACKS and FILE_ATTACKS as well as the corresponding masks. New attack tables BB_DIAG_ATTACKS (combined both diagonal tables), BB_RANK_ATTACKS and BB_FILE_ATTACKS are indexed by square instead of mask.
- board.push() no longer requires pseudo-legality.
- Documentation improvements.
Bugfixes:
- Positions in variant end are now guaranteed to have no legal moves. board.is_variant_end() has been added to test for special variant end conditions. Thanks to salvador-dali.
- chess.svg: Fixed a typo in the class names of black queens. Fixed fill color for black rooks and queens. Added SVG Tiny support. These combined changes fix display in a number of applications, including Jupyter Qt Console. Thanks to Alexander Meshcheryakov.
- board.ep_square was not consistently None instead of 0.
- Detect invalid racing kings positions: STATUS_RACE_OVER, STATUS_RACE_MATERIAL.
- SAN_REGEX, FEN_CASTLING_REGEX and TAG_REGEX now try to match the entire string and no longer accept newlines.
- Fixed Move.__hash__() for drops.
New features:
- board.remove_piece_at() now returns the removed piece.
- Added square_distance() and square_mirror().
- Added msb(), lsb(), scan_reversed() and scan_forward().
- Added BB_RAYS and BB_BETWEEN.
New in v0.16.2¶
Changes:
- board.move_stack now contains the exact move objects added with Board.push() (instead of normalized copies for castling moves). This ensures they can be used with Board.variation_san() amongst others.
- board.ep_square is now None instead of 0 for no en passant square.
- chess.svg: Better vector graphics for knights. Thanks to ProgramFox.
- Documentation improvements.
New in v0.16.1¶
Bugfixes:
- Explosions in atomic chess were not destroying castling rights. Thanks to ProgramFOX for finding this issue.
New in v0.16.0¶
Bugfixes:
- pin_mask(), pin() and is_pinned() make more sense when already in check. Thanks to Ferdinand Mosca.
New features:
- Variant support: Suicide, Giveaway, Atomic, King of the Hill, Racing Kings, Horde, Three-check, Crazyhouse. chess.Move now supports drops.
- More fine grained dependencies. Use pip install python-chess[uci,gaviota] to install dependencies for the full feature set.
- Added chess.STATUS_EMPTY and chess.STATUS_ILLEGAL_CHECK.
- The board.promoted mask keeps track of promoted pieces.
- Optionally copy boards without the move stack: board.copy(stack=False).
- examples/bratko_kopec now supports avoid move (am), variants and displays fractional scores immidiately. Thanks to Daniel Dugovic.
- perft.py rewritten with multi-threading support and moved to examples/perft.
- chess.syzygy.dependencies(), chess.syzygy.all_dependencies() to generate Syzygy tablebase dependencies.
Changes:
- Endgame tablebase probing (Syzygy, Gaviota): probe_wdl() , probe_dtz() and probe_dtm() now raise KeyError or MissingTableError instead of returning None. If you prefer getting None in case of an error use get_wdl(), get_dtz() and get_dtm().
- chess.pgn.BaseVisitor.result() returns True by default and is no longer used by chess.pgn.read_game() if no game was found.
- Non-fast-forward update of the Git repository to reduce size (old binary test assets removed).
- board.pop() now uses a boardstate stack to undo moves.
- uci.engine.position() will send the move history only until the latest zeroing move.
- Optimize board.clean_castling_rights() and micro-optimizations improving PGN parser performance by around 20%.
- Syzygy tables now directly use the endgame name as hash keys.
- Improve test performance (especially on Travis CI).
- Documentation updates and improvements.
New in v0.15.3¶
Bugfixes:
- pgn.Game.errors was not populated as documented. Thanks to Ryan Delaney for reporting.
New features:
- Added pgn.GameNode.add_line() and pgn.GameNode.main_line() which make it easier to work with lists of moves as variations.
New in v0.15.2¶
Bugfixes:
- Fix a bug where shift_right() and shift_2_right() were producing integers larger than 64bit when shifting squares off the board. This is very similar to the bug fixed in v0.15.1. Thanks to piccoloprogrammatore for reporting.
New in v0.15.1¶
Bugfixes:
- Fix a bug where shift_up_right() and shift_up_left() were producing integers larger than 64bit when shifting squares off the board.
New features:
- Replaced __html__ with experimental SVG rendering for IPython.
New in v0.15.0¶
Changes:
- chess.uci.Score no longer has upperbound and lowerbound attributes. Previously these were always False.
- Significant improvements of move generation speed, around 2.3x faster PGN parsing. Removed the following internal attributes and methods of the Board class: attacks_valid, attacks_to, attacks_from, _pinned(), attacks_valid_stack, attacks_from_stack, attacks_to_stack, generate_attacks().
- UCI: Do not send isready directly after go. Though allowed by the UCI protocol specification it is just not nescessary and many engines were having trouble with this.
- Polyglot: Use less memory for uniform random choices from big opening books (reservoir sampling).
- Documentation improvements.
Bugfixes:
- Allow underscores in PGN header tags. Found and fixed by Bajusz Tamás.
New features:
- Added Board.chess960_pos() to identify the Chess960 starting position number of positions.
- Added chess.BB_BACKRANKS and chess.BB_PAWN_ATTACKS.
New in v0.14.1¶
Bugfixes:
- Backport Bugfix for Syzygy DTZ related to en-passant. See official-stockfish/Stockfish@6e2ca97d93812b2.
Changes:
- Added optional argument max_fds=128 to chess.syzygy.open_tablebases(). An LRU cache is used to keep at most max_fds files open. This allows using many tables without running out of file descriptors. Previously all tables were opened at once.
- Syzygy and Gaviota now store absolute tablebase paths, in case you change the working directory of the process.
- The default implementation of chess.uci.InfoHandler.score() will no longer store score bounds in info[“score”], only real scores.
- Added Board.set_chess960_pos().
- Documentation improvements.
New in v0.14.0¶
Changes:
Board.attacker_mask() has been renamed to Board.attackers_mask() for consistency.
The signature of Board.generate_legal_moves() and Board.generate_pseudo_legal_moves() has been changed. Previously it was possible to select piece types for selective move generation:
Board.generate_legal_moves(castling=True, pawns=True, knights=True, bishops=True, rooks=True, queens=True, king=True)
Now it is possible to select arbitrary sets of origin and target squares. to_mask uses the corresponding rook squares for castling moves.
Board.generate_legal_moves(from_mask=BB_ALL, to_mask=BB)
To generate all knight and queen moves do:
board.generate_legal_moves(board.knights | board.queens)
To generate only castling moves use:
Board.generate_castling_moves(from_mask=BB_ALL, to_mask=BB_ALL)
Additional hardening has been added on top of the bugfix from v0.13.3. Diagonal skewers on the last double pawn move are now handled correctly, even though such positions can not be reached with a sequence of legal moves.
chess.syzygy now uses the more efficient selective move generation.
New features:
- The following move generation methods have been added: Board.generate_pseudo_legal_ep(from_mask=BB_ALL, to_mask=BB_ALL), Board.generate_legal_ep(from_mask=BB_ALL, to_mask=BB_ALL), Board.generate_pseudo_legal_captures(from_mask=BB_ALL, to_mask=BB_ALL), Board.generate_legal_captures(from_mask=BB_ALL, to_mask=BB_ALL).
New in v0.13.3¶
This is a bugfix release for a move generation bug. Other than the bugfix itself there are only minimal fully backwardscompatible changes. You should update immediately.
Bugfixes:
When capturing en passant, both the capturer and the captured pawn disappear from the fourth or fifth rank. If those pawns were covering a horizontal attack on the king, then capturing en passant should not have been legal.
Board.generate_legal_moves() and Board.is_into_check() have been fixed.
The same principle applies for diagonal skewers, but nothing has been done in this release: If the last double pawn move covers a diagonal attack, then the king would have already been in check.
v0.14.0 adds additional hardening for all cases. It is recommended you upgrade to v0.14.0 as soon as you can deal with the non-backwards compatible changes.
Changes:
- chess.uci now uses subprocess32 if applicable (and available). Additionally a lock is used to work around a race condition in Python 2, that can occur when spawning engines from multiple threads at the same time.
- Consistently handle tabs in UCI engine output.
New in v0.13.2¶
Changes:
- chess.syzygy.open_tablebases() now raises if the given directory does not exist.
- Allow visitors to handle invalid FEN tags in PGNs.
- Gaviota tablebase probing fails faster for piece counts > 5.
Minor new features:
- Added chess.pgn.Game.from_board().
New in v0.13.1¶
Changes:
- Missing SetUp tags in PGNs are ignored.
- Incompatible comparisons on chess.Piece, chess.Move, chess.Board and chess.SquareSet now return NotImplemented instead of False.
Minor new features:
- Factored out basic board operations to chess.BaseBoard. This is inherited by chess.Board and extended with the usual move generation features.
- Added optional claim_draw argument to chess.Base.is_game_over().
- Added chess.Board.result(claim_draw=False).
- Allow chess.Board.set_piece_at(square, None).
- Added chess.SquareSet.from_square(square).
New in v0.13.0¶
- chess.pgn.Game.export() and chess.pgn.GameNode.export() have been removed and replaced with a new visitor concept.
- chess.pgn.read_game() no longer takes an error_handler argument. Errors are now logged. Use the new visitor concept to change this behaviour.
New in v0.12.5¶
Bugfixes:
- Context manager support for pure Python Gaviota probing code. Various documentation fixes for Gaviota probing. Thanks to Jürgen Précour for reporting.
- PGN variation start comments for variations on the very first move were assigned to the game. Thanks to Norbert Räcke for reporting.
New in v0.12.4¶
Bugfixes:
- Another en passant related Bugfix for pure Python Gaviota tablebase probing.
New features:
- Added pgn.GameNode.is_end().
Changes:
- Big speedup for pgn module. Boards are cached less agressively. Board move stacks are copied faster.
- Added tox.ini to specify test suite and flake8 options.
New in v0.12.3¶
Bugfixes:
- Some invalid castling rights were silently ignored by Board.set_fen(). Now it is ensured information is stored for retrieval using Board.status().
New in v0.12.2¶
Bugfixes:
- Some Gaviota probe results were incorrect for positions where black could capture en passant.
New in v0.12.1¶
Changes:
- Robust handling of invalid castling rights. You can also use the new method Board.clean_castling_rights() to get the subset of strictly valid castling rights.
New in v0.12.0¶
New features:
- Python 2.6 support. Patch by vdbergh.
- Pure Python Gaviota tablebase probing. Thanks to Jean-Noël Avila.
New in v0.11.1¶
Bugfixes:
- syzygy.Tablebases.probe_dtz() has was giving wrong results for some positions with possible en passant capturing. This was found and fixed upstream: https://github.com/official-stockfish/Stockfish/issues/394.
- Ignore extra spaces in UCI info lines, as for example sent by the Hakkapeliitta engine. Thanks to Jürgen Précour for reporting.
New in v0.11.0¶
Changes:
Chess960 support and the representation of castling moves has been changed.
The constructor of board has a new chess960 argument, defaulting to False: Board(fen=STARTING_FEN, chess960=False). That property is available as Board.chess960.
In Chess960 mode the behaviour is as in the previous release. Castling moves are represented as a king move to the corresponding rook square.
In the default standard chess mode castling moves are represented with the standard UCI notation, e.g. e1g1 for king-side castling.
Board.uci(move, chess960=None) creates UCI representations for moves. Unlike Move.uci() it can convert them in the context of the current position.
Board.has_chess960_castling_rights() has been added to test for castling rights that are impossible in standard chess.
The modules chess.polyglot, chess.pgn and chess.uci will transparently handle both modes.
In a previous release Board.fen() has been changed to only display an en passant square if a legal en passant move is indeed possible. This has now also been adapted for Board.shredder_fen() and Board.epd().
New features:
- Get individual FEN components: Board.board_fen(), Board.castling_xfen(), Board.castling_shredder_fen().
- Use Board.has_legal_en_passant() to test if a position has a legal en passant move.
- Make repr(board.legal_moves) human readable.
New in v0.10.0¶
New dependencies:
- If you are using Python < 3.2 you have to install futures in order to use the chess.uci module.
Changes:
There are big changes in the UCI module. Most notably in async mode multiple commands can be executed at the same time (e.g. go infinite and then stop or go ponder and then ponderhit).
go infinite and go ponder will now wait for a result, i.e. you may have to call stop or ponderhit from a different thread or run the commands asynchronously.
stop and ponderhit no longer have a result.
The values of the color constants chess.WHITE and chess.BLACK have been changed. Previously WHITE was 0, BLACK was 1. Now WHITE is True, BLACK is False. The recommended way to invert color is using not color.
The pseudo piece type chess.NONE has been removed in favor of just using None.
Changed the Board(fen) constructor. If the optional fen argument is not given behavior did not change. However if None is passed explicitly an empty board is created. Previously the starting position would have been set up.
Board.fen() will now only show completely legal en passant squares.
Board.set_piece_at() and Board.remove_piece_at() will now clear the move stack, because the old moves may not be valid in the changed position.
Board.parse_uci() and Board.push_uci() will now accept null moves.
Changed shebangs from #!/usr/bin/python to #!/usr/bin/env python for better virtualenv support.
Removed unused game data files from repository.
Bugfixes:
- PGN: Prefer the game result from the game termination marker over * in the header. These should be identical in standard compliant PGNs. Thanks to Skyler Dawson for reporting this.
- Polyglot: minimum_weight for find(), find_all() and choice() was not respected.
- Polyglot: Negative indexing of opening books was raising IndexError.
- Various documentation fixes and improvements.
New features:
Experimental probing of Gaviota tablebases via libgtb.
New methods to construct boards:
>>> chess.Board.empty() Board('8/8/8/8/8/8/8/8 w - - 0 1') >>> board, ops = chess.Board.from_epd("4k3/8/8/8/8/8/8/4K3 b - - fmvn 17; hmvc 13") >>> board Board('4k3/8/8/8/8/8/8/4K3 b - - 13 17') >>> ops {'fmvn': 17, 'hmvc': 13}
Added Board.copy() and hooks to let the copy module to the right thing.
Added Board.has_castling_rights(color), Board.has_kingside_castling_rights(color) and Board.has_queenside_castling_rights(color).
Added Board.clear_stack().
Support common set operations on chess.SquareSet().
New in v0.9.1¶
Bugfixes:
- UCI module could not handle castling ponder moves. Thanks to Marco Belli for reporting.
- The initial move number in PGNs was missing, if black was to move in the starting position. Thanks to Jürgen Précour for reporting.
- Detect more impossible en passant squares in Board.status(). There already was a requirement for a pawn on the fifth rank. Now the sixth and seventh rank must be empty, additionally. We do not do further retrograde analysis, because these are the only cases affecting move generation.
New in v0.8.3¶
Bugfixes:
- The initial move number in PGNs was missing, if black was to move in the starting position. Thanks to Jürgen Précour for reporting.
- Detect more impossible en passant squares in Board.status(). There already was a requirement for a pawn on the fifth rank. Now the sixth and seventh rank must be empty, additionally. We do not do further retrograde analysis, because these are the only cases affecting move generation.
New in v0.9.0¶
This is a big update with quite a few breaking changes. Carefully review the changes before upgrading. It’s no problem if you can not update right now. The 0.8.x branch still gets bugfixes.
Incompatible changes:
Removed castling right constants. Castling rights are now represented as a bitmask of the rook square. For example:
>>> board = chess.Board() >>> # Standard castling rights. >>> board.castling_rights == chess.BB_A1 | chess.BB_H1 | chess.BB_A8 | chess.BB_H8 True >>> # Check for the presence of a specific castling right. >>> can_white_castle_queenside = chess.BB_A1 & board.castling_rights
Castling moves were previously encoded as the corresponding king movement in UCI, e.g. e1f1 for white kingside castling. Now castling moves are encoded as a move to the corresponding rook square (UCI_Chess960-style), e.g. e1a1.
You may use the new methods Board.uci(move, chess960=True), Board.parse_uci(uci) and Board.push_uci(uci) to handle this transparently.
The uci module takes care of converting moves when communicating with an engine that is not in UCI_Chess960 mode.
The get_entries_for_position(board) method of polyglot opening book readers has been changed to find_all(board, minimum_weight=1). By default entries with weight 0 are excluded.
The Board.pieces lookup list has been removed.
In 0.8.1 the spelling of repetition (was repitition) was fixed. can_claim_threefold_repetition() and is_fivefold_repetition() are the affected method names. Aliases are now removed.
Board.set_epd() will now interpret bm, am as a list of moves for the current position and pv as a variation (represented by a list of moves). Thanks to Jordan Bray for reporting this.
Removed uci.InfoHandler.pre_bestmove() and uci.InfoHandler.post_bestmove().
uci.InfoHandler().info[“score”] is now relative to multipv. Use
>>> with info_handler as info: ... if 1 in info["score"]: ... cp = info["score"][1].cp
where you were previously using
>>> with info_handler as info: ... if "score" in info: ... cp = info["score"].cp
Clear uci.InfoHandler() dictionary at the start of new searches (new on_go()), not at the end of searches.
Renamed PseudoLegalMoveGenerator.bitboard and LegalMoveGenerator.bitboard to PseudoLegalMoveGenerator.board and LegalMoveGenerator.board, respectively.
Scripts removed.
Python 3.2 compability dropped. Use Python 3.3 or higher. Python 2.7 support is not affected.
New features:
- Introduced Chess960 support. Board(fen) and Board.set_fen(fen) now support X-FENs. Added Board.shredder_fen(). Board.status(allow_chess960=True) has an optional argument allowing to insist on standard chess castling rules. Added Board.is_valid(allow_chess960=True).
- Improved move generation using Shatranj-style direct lookup. Removed rotated bitboards. Perft speed has been more than doubled.
- Added choice(board) and weighted_choice(board) for polyglot opening book readers.
- Added Board.attacks(square) to determine attacks from a given square. There already was Board.attackers(color, square) returning attacks to a square.
- Added Board.is_en_passant(move), Board.is_capture(move) and Board.is_castling(move).
- Added Board.pin(color, square) and Board.is_pinned(color, square).
- There is a new method Board.pieces(piece_type, color) to get a set of squares with the specified pieces.
- Do expensive Syzygy table initialization on demand.
- Allow promotions like e8Q (usually e8=Q) in Board.parse_san() and PGN files.
- Patch by Richard C. Gerkin: Added Board.__unicode__() just like Board.__str__() but with unicode pieces.
- Patch by Richard C. Gerkin: Added Board.__html__().
New in v0.8.2¶
Bugfixes:
- pgn.Game.setup() with the standard starting position was failing when the standard starting position was already set. Thanks to Jordan Bray for reporting this.
Optimizations:
- Remove bswap() from Syzygy decompression hot path. Directly read integers with the correct endianness.
New in v0.8.1¶
- Fixed pondering mode in uci module. For example ponderhit() was blocking indefinitely. Thanks to Valeriy Huz for reporting this.
- Patch by Richard C. Gerkin: Moved searchmoves to the end of the UCI go command, where it will not cause other command parameters to be ignored.
- Added missing check or checkmate suffix to castling SANs, e.g. O-O-O#.
- Fixed off-by-one error in polyglot opening book binary search. This would not have caused problems for real opening books.
- Fixed Python 3 support for reverse polyglot opening book iteration.
- Bestmoves may be literally (none) in UCI protocol, for example in checkmate positions. Fix parser and return None as the bestmove in this case.
- Fixed spelling of repetition (was repitition). can_claim_threefold_repetition() and is_fivefold_repetition() are the affected method names. Aliases are there for now, but will be removed in the next release. Thanks to Jimmy Patrick for reporting this.
- Added SquareSet.__reversed__().
- Use containerized tests on Travis CI, test against Stockfish 6, improved test coverage amd various minor clean-ups.
New in v0.8.0¶
- Implement Syzygy endgame tablebase probing. https://syzygy-tables.info is an example project that provides a public API using the new features.
- The interface for aynchronous UCI command has changed to mimic concurrent.futures. is_done() is now just done(). Callbacks will receive the command object as a single argument instead of the result. The result property and wait() have been removed in favor of a synchronously waiting result() method.
- The result of the stop and go UCI commands are now named tuples (instead of just normal tuples).
- Add alias Board for Bitboard.
- Fixed race condition during UCI engine startup. Lines received during engine startup sometimes needed to be processed before the Engine object was fully initialized.
New in v0.7.0¶
- Implement UCI engine communication.
- Patch by Matthew Lai: Add caching for gameNode.board().
New in v0.6.0¶
- If there are comments in a game before the first move, these are now assigned to Game.comment instead of Game.starting_comment. Game.starting_comment is ignored from now on. Game.starts_variation() is no longer true. The first child node of a game can no longer have a starting comment. It is possible to have a game with Game.comment set, that is otherwise completely empty.
- Fix export of games with variations. Previously the moves were exported in an unusual (i.e. wrong) order.
- Install gmpy2 or gmpy if you want to use slightly faster binary operations.
- Ignore superfluous variation opening brackets in PGN files.
- Add GameNode.san().
- Remove sparse_pop_count(). Just use pop_count().
- Remove next_bit(). Now use bit_scan().
New in v0.5.0¶
PGN parsing is now more robust: read_game() ignores invalid tokens. Still exceptions are going to be thrown on illegal or ambiguous moves, but this behaviour can be changed by passing an error_handler argument.
>>> # Raises ValueError: >>> game = chess.pgn.read_game(file_with_illegal_moves)
>>> # Silently ignores errors and continues parsing: >>> game = chess.pgn.read_game(file_with_illegal_moves, None)
>>> # Logs the error, continues parsing: >>> game = chess.pgn.read_game(file_with_illegal_moves, logger.exception)
If there are too many closing brackets this is now ignored.
Castling moves like 0-0 (with zeros) are now accepted in PGNs. The Bitboard.parse_san() method remains strict as always, though.
Previously the parser was strictly following the PGN spefification in that empty lines terminate a game. So a game like
[Event "?"] { Starting comment block } 1. e4 e5 2. Nf3 Nf6 *
would have ended directly after the starting comment. To avoid this, the parser will now look ahead until it finds at least one move or a termination marker like *, 1-0, 1/2-1/2 or 0-1.
Introduce a new function scan_headers() to quickly scan a PGN file for headers without having to parse the full games.
Minor testcoverage improvements.
New in v0.4.2¶
- Fix bug where pawn_moves_from() and consequently is_legal() weren’t handling en passant correctly. Thanks to Norbert Naskov for reporting.
New in v0.4.1¶
- Fix is_fivefold_repitition(): The new fivefold repetition rule requires the repetitions to occur on alternating consecutive moves.
- Minor testing related improvements: Close PGN files, allow running via setuptools.
- Add recently introduced features to README.
New in v0.4.0¶
- Introduce can_claim_draw(), can_claim_fifty_moves() and can_claim_threefold_repitition().
- Since the first of July 2014 a game is also over (even without claim by one of the players) if there were 75 moves without a pawn move or capture or a fivefold repetition. Let is_game_over() respect that. Introduce is_seventyfive_moves() and is_fivefold_repitition(). Other means of ending a game take precedence.
- Threefold repetition checking requires efficient hashing of positions to build the table. So performance improvements were needed there. The default polyglot compatible zobrist hashes are now built incrementally.
- Fix low level rotation operations l90(), l45() and r45(). There was no problem in core because correct versions of the functions were inlined.
- Fix equality and inequality operators for Bitboard, Move and Piece. Also make them robust against comparisons with incompatible types.
- Provide equality and inequality operators for SquareSet and polyglot.Entry.
- Fix return values of incremental arithmetical operations for SquareSet.
- Make polyglot.Entry a collections.namedtuple.
- Determine and improve test coverage.
- Minor coding style fixes.
New in v0.3.1¶
- Bitboard.status() now correctly detects STATUS_INVALID_EP_SQUARE, instead of errors or false reports.
- Polyglot opening book reader now correctly handles knight underpromotions.
- Minor coding style fixes, including removal of unused imports.
New in v0.3.0¶
Rename property half_moves of Bitboard to halfmove_clock.
Rename property ply of Bitboard to fullmove_number.
Let PGN parser handle symbols like !, ?, !? and so on by converting them to NAGs.
Add a human readable string representation for Bitboards.
>>> print(chess.Bitboard()) r n b q k b n r p p p p p p p p . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P P P P P P P P R N B Q K B N R
Various documentation improvements.
New in v0.2.0¶
- Implement PGN parsing and writing.
- Hugely improve test coverage and use Travis CI for continuous integration and testing.
- Create an API documentation.
- Improve Polyglot opening-book handling.
New in v0.1.0¶
Apply the lessons learned from the previous releases, redesign the API and implement it in pure Python.
New in v0.0.4¶
Implement the basics in C++ and provide bindings for Python. Obviously performance was a lot better - but at the expense of having to compile code for the target platform.
Pre v0.0.4¶
First experiments with a way too slow pure Python API, creating way too many objects for basic operations.