python-chess: a chess library for Python

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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:

.. code:: python

>>> 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 <https://python-chess.readthedocs.io/en/latest/>`__

Core <https://python-chess.readthedocs.io/en/latest/core.html>_
PGN parsing and writing <https://python-chess.readthedocs.io/en/latest/pgn.html>_
Polyglot opening book reading <https://python-chess.readthedocs.io/en/latest/polyglot.html>_
Gaviota endgame tablebase probing <https://python-chess.readthedocs.io/en/latest/gaviota.html>_
Syzygy endgame tablebase probing <https://python-chess.readthedocs.io/en/latest/syzygy.html>_
UCI/XBoard engine communication <https://python-chess.readthedocs.io/en/latest/engine.html>_
Variants <https://python-chess.readthedocs.io/en/latest/variant.html>_
Changelog <https://python-chess.readthedocs.io/en/latest/changelog.html>_

Features

Includes mypy typings.
IPython/Jupyter Notebook integration.
SVG rendering docs <https://python-chess.readthedocs.io/en/latest/svg.html>_.

.. code:: python
```
>>> board  # doctest: +SKIP
```
.. image:: https://backscattering.de/web-boardimage/board.png?fen=r1bqkb1r/pppp1Qpp/2n2n2/4p3/2B1P3/8/PPPP1PPP/RNB1K1NR&lastmove=h5f7&check=e8
:alt: 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 <https://python-chess.readthedocs.io/en/latest/variant.html>_.

Make and unmake moves.

.. code:: python

>>> 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.

.. code:: python

>>> 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.

.. code:: python

>>> 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.

.. code:: python
```
>>> 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.

.. code:: python
```
>>> board.is_fivefold_repetition()
False
>>> board.is_seventyfive_moves()
False
```

Detects checks and attacks.

.. code:: python

>>> 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.

.. code:: python

>>> 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.

.. code:: python

>>> 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.

.. code:: python

>>> 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 <https://python-chess.readthedocs.io/en/latest/core.html#chess.Board.pin>_.

Reads Polyglot opening books.
Docs <https://python-chess.readthedocs.io/en/latest/polyglot.html>__.

.. code:: python

>>> 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 <https://python-chess.readthedocs.io/en/latest/pgn.html>__.

.. code:: python

>>> 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 <https://python-chess.readthedocs.io/en/latest/gaviota.html>__.

Probe Syzygy endgame tablebases (DTZ, WDL).
Docs <https://python-chess.readthedocs.io/en/latest/syzygy.html>__.

.. code:: python

>>> 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 <https://python-chess.readthedocs.io/en/latest/engine.html>__.

.. code:: python

>>> 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:

+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/syzygy.png?raw=true | https://syzygy-tables.info/ |
| :height: 64 | |
| :width: 64 | |
| :target: https://syzygy-tables.info/ | A website to probe Syzygy endgame tablebases |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/maia.png?raw=true | https://maiachess.com/ |
| :height: 64 | |
| :width: 64 | |
| :target: https://maiachess.com/ | A human-like neural network chess engine |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/clente-chess.png?raw=true | clente/chess <https://github.com/clente/chess>_ |
| :height: 64 | |
| :width: 64 | |
| :target: https://github.com/clente/chess | Opinionated wrapper to use python-chess from the R programming language |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/crazyara.png?raw=true | https://crazyara.org/ |
| :height: 64 | |
| :width: 64 | |
| :target: https://crazyara.org/ | Deep learning for Crazyhouse |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/jcchess.png?raw=true | http://johncheetham.com <http://johncheetham.com/projects/jcchess/>_ |
| :height: 64 | |
| :width: 64 | |
| :target: http://johncheetham.com/projects/jcchess/ | A GUI to play against UCI chess engines |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/pettingzoo.png?raw=true | https://pettingzoo.farama.org <https://pettingzoo.farama.org/environments/classic/chess/>_ |
| :width: 64 | |
| :height: 64 | |
| :target: https://pettingzoo.farama.org/environments/classic/chess/ | A multi-agent reinforcement learning environment |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+
| .. image:: https://github.com/niklasf/python-chess/blob/master/docs/images/cli-chess.png?raw=true | cli-chess <https://github.com/trevorbayless/cli-chess>_ |
| :width: 64 | |
| :height: 64 | |
| :target: https://github.com/trevorbayless/cli-chess | A highly customizable way to play chess in your terminal |
+------------------------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------+

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 <https://jupyter.brynmawr.edu/services/public/dblank/CS371%20Cognitive%20Science/2016-Fall/Programming%20a%20Chess%20Player.ipynb>_
an Alexa skill to play blindfold chess <https://www.amazon.com/Laynr-blindfold-chess/dp/B0859QF8YL>_ – 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 <https://about.nmstoker.com/chess2.html>_ 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) <http://arxiv.org/pdf/0704.3773.pdf>_
alongside his GPL2+ engine Shatranj <https://github.com/stannous/shatranj>_.
Some move generation ideas are taken from these sources.

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 Kristian Glass <https://github.com/doismellburning>_ for
transferring the namespace chess on PyPI.