Changelog for python-chess

New in v1.9.0


  • Expand position validation to detect check conflicting with en passant square.

New features:

  • Add chess.svg.board(..., fill=...).

  • Let chess.svg.board() add ASCII board as description of SVG.

  • Add hint when engine process dies due to illegal instruction.

New in v1.8.0


  • Fix SquareSet.issuperset() and SquareSet.issubset() by swapping their respective implementations.

New features:

  • Read and write PGN comments like [%emt 0:05:21].

New in v1.7.0

New features:

  • Add new models for chess.engine.Score.wdl(): sf (the new default) and sf14.

  • Add chess.Board.piece_map().


  • chess.pgn: Fix skipping with nested variations.

  • chess.svg: Make check gradient compatible with QtSvg.

New in v1.6.1


  • Make, draw_offered=True) available. Previously only added for chess.engine.Protocol.

New in v1.6.0

New features:

  • Allow offering a draw to XBoard engines using, draw_offered=True).

  • Now detects insufficient material in Horde. Thanks @stevepapazis!


  • chess.engine.popen_engine(..., setpgrp=True) on Windows now merges CREATE_NEW_PROCESS_GROUP into creationflags instead of overriding. On Unix it now uses start_new_session instead of calling setpgrp in preexec_fn.

  • Declare that chess.svg produces SVG Tiny 1.2, and prepare SVG 2 forwards compatibility.


  • Fix slightly off-center pawns in chess.svg.

  • Fix typing error in Python 3.10 (due to added int.bit_count).

New in v1.5.0


  • Fixed typing of chess.pgn.Mainline.__reversed__(). It is now a generator, and chess.pgn.ReverseMainline has been removed. This is a breaking change but a required bugfix.

  • Implement UCI ponderhit for consecutive calls to, ponder=True). Previously, the pondering search was always stopped and restarted.

  • Provide the full move stack, not just the position, for UCI pondering.

  • Fixed XBoard level in sudden death games.

  • Ignore trailing space after ponder move sent by UCI engine. Previously, such a move would be rejected.

  • Prevent cancelling engine commands after they have already been cancelled or completed. Some internals (chess.engine.BaseCommand) have been changed to accomplish this.

New features:

  • Added chess.Board.outcome().

  • Implement and accept usermove feature for XBoard engines.

Special thanks to @MarkZH for many of the engine related changes in this release!

New in v1.4.0

New features:

  • Let chess.pgn.GameNode.eval() accept PGN comments like [%eval 2.5,11], meaning 250 centipawns at depth 11. Use chess.pgn.GameNode.eval_depth() and chess.pgn.GameNode.set_eval(..., depth) to get and set the depth.

  • Read and write PGN comments with millisecond precision like [%clk 1:23:45.678].


  • Recover from invalid UTF-8 sent by an UCI engine, by ignoring that (and only that) line.

New in v1.3.3


  • Fixed unintended collisions and optimized chess.Piece.__hash__().

  • Fixed false-positive chess.STATUS_IMPOSSIBLE_CHECK if checkers are aligned with other king.


  • Also detect chess.STATUS_IMPOSSIBLE_CHECK if checker is aligned with en passant square and king.

New features:

  • Implemented Lichess winning chance model for chess.engine.Score: score.wdl(model="lichess").

New in v1.3.2


  • Added a new reason for board.status() to be invalid: chess.STATUS_IMPOSSIBLE_CHECK. This detects positions where two sliding pieces are giving check while also being aligned with the king on the same rank, file, or diagonal. Such positions are impossible to reach, break Stockfish, and maybe other engines.

New in v1.3.1


  • chess.pgn.read_game() now properly detects variant games with Chess960 castling rights (as well as mislabeled Standard Chess960 games). Previously, all castling moves in such games were rejected.

New in v1.3.0


  • Introduced chess.pgn.ChildNode, a subclass of chess.pgn.GameNode for all nodes other than the root node, and converted chess.pgn.GameNode to an abstract base class. This improves ergonomics in typed code.

    The change is backwards compatible if using only documented features. However, a notable undocumented feature is the ability to create dangling nodes. This is no longer possible. If you have been using this for subclassing, override GameNode.add_variation() instead of GameNode.dangling_node(). It is now the only method that creates child nodes.


  • Removed broken weakref-based caching in chess.pgn.GameNode.board().

New features:

  • Added

New in v1.2.2


  • Fixed regression where releases were uploaded without the py.typed marker.

New in v1.2.1


New in v1.2.0

New features:

  • Added chess.Board.ply().

  • Added chess.pgn.GameNode.ply() and chess.pgn.GameNode.turn().

  • Added chess.engine.PovWdl, chess.engine.Wdl, and conversions from scores: chess.engine.PovScore.wdl(), chess.engine.Score.wdl().

  • Added chess.engine.Score.score(*, mate_score: int) -> int overload.


  • The PovScore returned by chess.pgn.GameNode.eval() is now always relative to the side to move. The ambiguity around [%eval #0] has been resolved to Mate(-0). This makes sense, given that the authors of the specification probably had standard chess in mind (where a game-ending move is always a loss for the opponent). Previously, this would be parsed as None.

  • Typed chess.engine.InfoDict["wdl"] as the new chess.engine.PovWdl, rather than Tuple[int, int, int]. The new type is backwards compatible, but it is recommended to use its documented fields and methods instead.

  • Removed chess.engine.PovScore.__str__(). String representation falls back to __repr__.

  • The en_passant parameter of chess.Board.fen() and chess.Board.epd() is now typed as Literal["legal", "fen", "xfen"] rather than str.

New in v1.1.0

New features:

  • Added chess.svg.board(..., orientation). This is a more idiomatic way to set the board orientation than flipped.

  • Added chess.svg.Arrow.pgn() and chess.svg.Arrow.from_pgn().


  • Further relaxed chess.Board.parse_san(). Now accepts fully specified moves like e2e4, even if that is not a pawn move, castling notation with zeros, null moves in UCI notation, and null moves in XBoard notation.

New in v1.0.1


  • chess.svg: Restored SVG Tiny compatibility by splitting colors like #rrggbbaa into a solid color and opacity.

New in v1.0.0

See CHANGELOG-OLD.rst for changes up to v1.0.0.