lu4 / chessmoves

Python C extension for chess move and position generation (SAN/FEN/UCI)

Chessmoves

Chess move and position (FEN/SAN/UCI) generation in C for use in scripting applications.

`Chessmoves' is a small module to make fast chess tree traversal available in a scripting environment, such as Python or sh.

In the core this is a set of C functions for chess move making, wrapped for easy use. All input and output is in the form of FEN strings for positions. SAN notation for moves is made available as well. The FEN output is strictly sanitized. For example, no fake en-passant target square flag is produced when there is no such legal capture in the position in the first place.

Python module interface:

NAME
    chessmoves - Chess move and position generation (SAN/FEN/UCI).

FUNCTIONS
    moves(...)
        moves(position, notation='san') -> { move : newPosition, ... }

        Generate all legal moves from a position.
        Return the result as a dictionary, mapping moves to positions.

        The `notation' keyword controls the output move syntax.
        Available notations are:
            'san': Standard Algebraic Notation (e.g. Nc3+, O-O, dxe8=Q)
            'long': Long Algebraic Notation (e.g. Nb1-c3+, O-O, d7xe8=Q)
            'uci': Universal Chess Interface computer notation (e.g. b1c3, e8g8, d7e8q)

    position(...)
        position(inputFen) -> standardFen

        Parse a FEN like string and convert it into a standardized FEN.
        For example:
         - Complete shortened ranks
         - Order castling flags
         - Remove en passant target square if there is no such legal capture
         - Remove excess data beyond the FEN

    move(...)
        move(inputFen, inputMove, notation='san') -> (move, fen)

        Try to parse the input move and return it as a normalized string
        if successful, legal and unambiguous.

        The parser accepts a wide variety of formats. The only restriction
        is that piece identifiers, other than promotion pieces, must always
        be in upper case, and file letters must always be in lower case.
        Input capture signs, check marks, checkmate marks, annotations
        (x, +, !, ?, etc) are all swallowed and ignored: these are not used
        for disambiguation and also not checked for correctness.
        When a promotion piece is missing, queening is assumed.
        The output fen is the position after the move.

        The `notation' keyword controls the output move syntax. See moves(...)
        for details.

   hash(...)
        hash(fen) -> hash

        Compute the Zobrist-Polyglot hash for the position.

DATA
    notations = ['uci', 'san', 'long']
    startPosition = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - ...

Example of the Python extension:

>>> import chessmoves
>>> moves = chessmoves.moves(chessmoves.startPosition)
>>> print moves.keys()
['g3', 'f3', 'f4', 'h3', 'Nc3', 'h4', 'b4', 'Na3', 'a3', 'g4', 'Nf3', 'a4', 'Nh3', 'b3', 'c3', 'e4', 'd4', 'd3', 'e3', 'c4']
>>> print moves['e4']
rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq -

Performance of the Python extension:

$ echo rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - | time python Tools/perft.py 5
4865609
        3.08 real         3.06 user         0.00 sys
# --> results per second: 1,579,743