python-chess: a pure Python chess library

Introduction

python-chess is a pure Python chess library with move generation and validation and handling of common formats. This is the scholars mate in python-chess:

>>> import chess

>>> board = chess.Board()

>>> board.legal_moves  # doctest: +ELLIPSIS
<LegalMoveGenerator at ... (Na3, Nc3, Nf3, Nh3, a3, b3, c3, d3, e3, f3, g3, h3, ...)>
>>> 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')

Documentation

https://python-chess.readthedocs.io/en/latest/

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

Features

• Supports Python 2.6+, Python 3.3+ and PyPy.

• IPython 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.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 drawn (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(0b0000000000000000000000000000000000000000000000000100000001000000)
  >>> 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.

• Read 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()

• Read and write PGNs. Supports headers, comments, NAGs and a tree of variations. Docs.

  >>> import chess.pgn
  
  >>> pgn = open("data/pgn/molinari-bordais-1979.pgn")
  >>> first_game = chess.pgn.read_game(pgn)
  >>> pgn.close()
  
  >>> first_game.headers["White"]
  'Molinari'
  >>> first_game.headers["Black"]
  'Bordais'
  
  >>> # Get the mainline as a list of moves.
  >>> moves = first_game.main_line()
  >>> first_game.board().variation_san(moves)
  '1. e4 c5 2. c4 Nc6 3. Ne2 Nf6 4. Nbc3 Nb4 5. g3 Nd3#'
  
  >>> # Iterate through the mainline of this embarrasingly short game.
  >>> node = first_game
  >>> while not node.is_end():
  ...     next_node = node.variation(0)
  ...     print(node.board().san(next_node.move))
  ...     node = next_node
  e4
  c5
  c4
  Nc6
  Ne2
  Nf6
  Nbc3
  Nb4
  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
  
  >>> tablebases = chess.syzygy.open_tablebases("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")
  >>> tablebases.probe_dtz(board)
  -53
  
  >>> tablebases.close()

• Communicate with an UCI engine. Docs.

  >>> import chess.uci
  
  >>> engine = chess.uci.popen_engine("stockfish")
  >>> engine.uci()
  >>> engine.author  # doctest: +SKIP
  '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 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

Installing

Download and install the latest release:

pip install python-chess[uci,gaviota]

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/
• an HTTP microservice to render board images - https://github.com/niklasf/web-boardimage
• a bot to play chess on Telegram - https://github.com/cxjdavin/tgchessbot
• connecting Stockfish to the Novag Citrine - http://empiricalrabbit.blogspot.de/2016/05/integrating-with-python-chess-module.html
• a tool to build Anki decks from a PGN opening repertoire - https://github.com/asdfjkl/pgn2anki

License

python-chess is licensed under the GPL3. See the LICENSE file for the full copyright and license information.

Thanks to Sam Tannous for publishing his approach to avoid rotated bitboards with direct lookup (pdf) alongside his GPL2+ engine Shatranj. Some of the bitboard move generation parts are ported from there.

Thanks to Ronald de Man for his Syzygy endgame tablebases (https://github.com/syzygy1/tb). The probing code in python-chess is very directly ported from his C probing code.

Thanks to Miguel A. Ballicora for his Gaviota tablebases (https://github.com/michiguel/Gaviota-Tablebases).