python-chess: a pure Python chess library

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Introduction

This is the scholars mate in python-chess:

>>> import chess

>>> board = chess.Bitboard()

>>> 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

Features

  • Legal move generator and move validation. This includes all castling rules and en-passant captures.

    >>> chess.Move.from_uci("a8a1") in board.legal_moves
False

  • Make and unmake moves.

    >>> Qf7 = board.pop() # Unmake last move (Qf7#)
>>> Qf7
Move.from_uci('h5f7')

>>> board.push(Qf7) # Restore

  • Detects checkmates, stalemates and draws by insufficient material. Has a half-move clock.

    >>> board.is_stalemate()
False
>>> board.is_insufficient_material()
False
>>> board.is_game_over()
True
>>> board.half_moves
0

  • 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(0b100000001000000)
>>> chess.G2 in attackers
True

  • Parses and creates SAN representation of moves.

    >>> board = chess.Bitboard()
>>> board.san(chess.Move(chess.E2, chess.E4))
'e4'

  • Parses and creates FENs.

    >>> board.fen()
'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1'
>>> board = chess.Bitboard("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.Bitboard()
>>> board.epd(bm=chess.Move.from_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

  • Read Polyglot opening books.

    >>> import chess.polyglot

>>> book = chess.polyglot.open_reader("data/opening-books/performance.bin")
>>> board = chess.Bitboard()
>>> first_entry = next(book.get_entries_for_position(board))
>>> first_entry.move()
Move.from_uci('e2e4')
>>> first_entry.learn
0
>>> first_entry.weight
1

>>> book.close()

  • Read and write PGNs.

    >>> import chess.pgn

>>> pgn = open("data/games/kasparov-deep-blue-1997.pgn")
>>> first_game = chess.pgn.read_game(pgn)
>>> pgn.close()

>>> first_game.headers["White"]
'Garry Kasparov'
>>> first_game.headers["Result"]
'1-0'

Peformance

python-chess is not intended to be used by serious chess engines where performance is critical. The goal is rather to create a simple and relatively highlevel library.

However, even though bit fiddling in Python is not as fast as in C or C++, the current version is still much faster than previous attempts including the naive x88 move generation from libchess.

Installing

  • With pip:

    sudo pip install python-chess

  • From current source code:

    python setup.py build
sudo python setup.py install

License

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

Thanks to the developers of http://chessx.sourceforge.net/. Some of the core bitboard move generation parts are ported from there.

Indices and tables