python-chess: a chess library for Python

Introduction

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:

>>>importchess>>>board=chess.Board()
>>>board.legal_moves# doctest: +ELLIPSIS<LegalMoveGeneratorat ... (Nh3, Nf3, Nc3, Na3, h3, g3, f3, e3, d3, c3, ...)>>>>chess.Move.from_uci("a8a1") inboard.legal_movesFalse>>>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>>>boardBoard('r1bqkb1r/pppp1Qpp/2n2n2/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR b KQkq - 0 4')

Installing

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

pip install chess

Documentation

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

Features

• 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 moveMove.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 . bqkb . rpppp . Qpp
  . . n . . n . .
  . . . . p . . .
  . . B . P . . .
  . . . . . . . .
  PPPP . PPPRNB . K . NR

• 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_clock0>>>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)
  >>>attackersSquareSet(0x0000_0000_0000_4040)
  >>>chess.G2inattackersTrue>>>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) formin ["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.

  >>>importchess.polyglot>>>book=chess.polyglot.open_reader("data/polyglot/performance.bin")
  >>>board=chess.Board()
  >>>main_entry=book.find(board)
  >>>main_entry.moveMove.from_uci('e2e4')
  >>>main_entry.weight1>>>book.close()

• Reads and writes PGNs. Supports headers, comments, NAGs and a tree of variations. Docs.

  >>>importchess.pgn>>>withopen("data/pgn/molinari-bordais-1979.pgn") aspgn:
  ... first_game=chess.pgn.read_game(pgn)
  >>>first_game.headers["White"]
  'Molinari'>>>first_game.headers["Black"]
  'Bordais'>>>first_game.mainline() # doctest: +ELLIPSIS<Mainlineat ... (1.e4c52.c4Nc63.Ne2Nf64.Nbc3Nb45.g3Nd3#)>>>>first_game.headers["Result"]
  '0-1'

• Probe Gaviota endgame tablebases (DTM, WDL). Docs.

• Probe Syzygy endgame tablebases (DTZ, WDL). Docs.

  >>>importchess.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.

  >>>importchess.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<PlayResultat ... (move=d6d1, ponder=c1d1, info={...}, draw_offered=False, resigned=False)>>>>engine.quit()

Selected projects

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

Prior art

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.

License

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