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python-chess: a chess library for Python

Test status PyPI package Docs Chat on Gitter

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:

>>> import chess

>>> board = chess.Board()

>>> board.legal_moves  # doctest: +ELLIPSIS
<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')

Installing

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

pip install chess

Documentation

Features

  • Includes mypy typings.

  • IPython/Jupyter Notebook integration. SVG rendering docs.

    >>> board  # doctest: +SKIP
    r1bqkb1r/pppp1Qpp/2n2n2/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR

  • 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()

Selected projects

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

https://github.com/niklasf/python-chess/blob/master/docs/images/syzygy.png?raw=true

https://syzygy-tables.info/

A website to probe Syzygy endgame tablebases
https://github.com/niklasf/python-chess/blob/master/docs/images/maia.png?raw=true

https://maiachess.com/

A human-like neural network chess engine
https://github.com/niklasf/python-chess/blob/master/docs/images/clente-chess.png?raw=true

clente/chess

Oppinionated wrapper to use python-chess from the R programming language
https://github.com/niklasf/python-chess/blob/master/docs/images/crazyara.png?raw=true

https://crazyara.org/

Deep learning for Crazyhouse
https://github.com/niklasf/python-chess/blob/master/docs/images/jcchess.png?raw=true

http://johncheetham.com

A GUI to play against UCI chess engines
https://github.com/niklasf/python-chess/blob/master/docs/images/pettingzoo.png?raw=true

https://pettingzoo.farama.org

A multi-agent reinforcement learning environment
https://github.com/niklasf/python-chess/blob/master/docs/images/cli-chess.png?raw=true

cli-chess

A highly customizable way to play chess in your terminal

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.