python-chess is a chess library for Python, with move generation, move validation, and support for common formats. This is the Scholar's mate in python-chess:

Requires Python 3.8+. Download and install the latest release:

• Core
• PGN parsing and writing
• Polyglot opening book reading
• Gaviota endgame tablebase probing
• Syzygy endgame tablebase probing
• UCI/XBoard engine communication
• Variants
• Changelog

• Includes mypy typings.

• IPython/Jupyter Notebook integration. SVG rendering docs.

  >>> board # doctest: +SKIP

• 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.outcome() Outcome(termination=<Termination.CHECKMATE: 1>, winner=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(0x0000_0000_0000_4040) >>> 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 >>> 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() # doctest: +ELLIPSIS <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 UCI/XBoard engines. Based on asyncio. Docs.

  >>> import chess.engine >>> engine = chess.engine.SimpleEngine.popen_uci("stockfish") >>> board = chess.Board("1k1r4/pp1b1R2/3q2pp/4p3/2B5/4Q3/PPP2B2/2K5 b - - 0 1") >>> limit = chess.engine.Limit(time=2.0) >>> engine.play(board, limit) # doctest: +ELLIPSIS <PlayResult at ... (move=d6d1, ponder=c1d1, info={...}, draw_offered=False, resigned=False)> >>> engine.quit()

If you like, share interesting things you are using python-chess for, for example:

• extensions to build engines (search and evaluation) – https://github.com/Mk-Chan/python-chess-engine-extensions
• a stand-alone chess computer based on DGT board – https://picochess.com/
• a bridge between Lichess API and chess engines – https://github.com/lichess-bot-devs/lichess-bot
• a command-line PGN annotator – https://github.com/rpdelaney/python-chess-annotator
• an HTTP microservice to render board images – https://github.com/niklasf/web-boardimage
• building a toy chess engine with alpha-beta pruning, piece-square tables, and move ordering – https://healeycodes.com/building-my-own-chess-engine/
• a JIT compiled chess engine – https://github.com/SamRagusa/Batch-First
• teaching Cognitive Science – https://jupyter.brynmawr.edu
• an Alexa skill to play blindfold chess – https://github.com/laynr/blindfold-chess
• a chessboard widget for PySide2 – https://github.com/H-a-y-k/hichesslib
• Django Rest Framework API for multiplayer chess – https://github.com/WorkShoft/capablanca-api
• a browser based PGN viewer written in PyScript – https://github.com/nmstoker/ChessMatchViewer
• an accessible chessboard that allows blind and visually impaired players to play chess against Stockfish – https://github.com/blindpandas/chessmart
• a web-based chess vision exercise – https://github.com/3d12/rookognition

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 Kristian Glass for transferring the namespace chess on PyPI.

python-chess is licensed under the GPL 3 (or any later version at your option). Check out LICENSE.txt for the full text.