Source code for chess

# -*- coding: utf-8 -*-
#
# This file is part of the python-chess library.
# Copyright (C) 2012-2019 Niklas Fiekas <niklas.fiekas@backscattering.de>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

"""
A pure Python chess library with move generation and validation, Polyglot
opening book probing, PGN reading and writing, Gaviota tablebase probing,
Syzygy tablebase probing and XBoard/UCI engine communication.
"""

__author__ = "Niklas Fiekas"

__email__ = "niklas.fiekas@backscattering.de"

__version__ = "0.27.3"

import collections
import copy
import enum
import re
import itertools
import typing

from typing import ClassVar, Callable, Dict, Generic, Hashable, Iterable, Iterator, List, Mapping, MutableSet, Optional, SupportsInt, Tuple, Type, TypeVar, Union


Color = bool
COLORS = [WHITE, BLACK] = [True, False]
COLOR_NAMES = ["black", "white"]

PieceType = int
PIECE_TYPES = [PAWN, KNIGHT, BISHOP, ROOK, QUEEN, KING] = range(1, 7)
PIECE_SYMBOLS = [None, "p", "n", "b", "r", "q", "k"]
PIECE_NAMES = [None, "pawn", "knight", "bishop", "rook", "queen", "king"]

def piece_symbol(piece_type: PieceType, _PIECE_SYMBOLS: List[Optional[str]] = PIECE_SYMBOLS) -> str:
    return typing.cast(str, _PIECE_SYMBOLS[piece_type])

UNICODE_PIECE_SYMBOLS = {
    "R": u"♖", "r": u"♜",
    "N": u"♘", "n": u"♞",
    "B": u"♗", "b": u"♝",
    "Q": u"♕", "q": u"♛",
    "K": u"♔", "k": u"♚",
    "P": u"♙", "p": u"♟",
}

FILE_NAMES = ["a", "b", "c", "d", "e", "f", "g", "h"]

RANK_NAMES = ["1", "2", "3", "4", "5", "6", "7", "8"]

STARTING_FEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
"""The FEN for the standard chess starting position."""

STARTING_BOARD_FEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
"""The board part of the FEN for the standard chess starting position."""


try:
    _IntFlag = enum.IntFlag  # Since Python 3.6
except AttributeError:
    _IntFlag = enum.IntEnum  # type: ignore

class Status(_IntFlag):
    VALID = 0
    NO_WHITE_KING = 1
    NO_BLACK_KING = 2
    TOO_MANY_KINGS = 4
    TOO_MANY_WHITE_PAWNS = 8
    TOO_MANY_BLACK_PAWNS = 16
    PAWNS_ON_BACKRANK = 32
    TOO_MANY_WHITE_PIECES = 64
    TOO_MANY_BLACK_PIECES = 128
    BAD_CASTLING_RIGHTS = 256
    INVALID_EP_SQUARE = 512
    OPPOSITE_CHECK = 1024
    EMPTY = 2048
    RACE_CHECK = 4096
    RACE_OVER = 8192
    RACE_MATERIAL = 16384

STATUS_VALID = Status.VALID
STATUS_NO_WHITE_KING = Status.NO_WHITE_KING
STATUS_NO_BLACK_KING = Status.NO_BLACK_KING
STATUS_TOO_MANY_KINGS = Status.TOO_MANY_KINGS
STATUS_TOO_MANY_WHITE_PAWNS = Status.TOO_MANY_WHITE_PAWNS
STATUS_TOO_MANY_BLACK_PAWNS = Status.TOO_MANY_BLACK_PAWNS
STATUS_PAWNS_ON_BACKRANK = Status.PAWNS_ON_BACKRANK
STATUS_TOO_MANY_WHITE_PIECES = Status.TOO_MANY_WHITE_PIECES
STATUS_TOO_MANY_BLACK_PIECES = Status.TOO_MANY_BLACK_PIECES
STATUS_BAD_CASTLING_RIGHTS = Status.BAD_CASTLING_RIGHTS
STATUS_INVALID_EP_SQUARE = Status.INVALID_EP_SQUARE
STATUS_OPPOSITE_CHECK = Status.OPPOSITE_CHECK
STATUS_EMPTY = Status.EMPTY
STATUS_RACE_CHECK = Status.RACE_CHECK
STATUS_RACE_OVER = Status.RACE_OVER
STATUS_RACE_MATERIAL = Status.RACE_MATERIAL


Square = int
SQUARES = [
    A1, B1, C1, D1, E1, F1, G1, H1,
    A2, B2, C2, D2, E2, F2, G2, H2,
    A3, B3, C3, D3, E3, F3, G3, H3,
    A4, B4, C4, D4, E4, F4, G4, H4,
    A5, B5, C5, D5, E5, F5, G5, H5,
    A6, B6, C6, D6, E6, F6, G6, H6,
    A7, B7, C7, D7, E7, F7, G7, H7,
    A8, B8, C8, D8, E8, F8, G8, H8,
] = range(64)

SQUARE_NAMES = [f + r for r in RANK_NAMES for f in FILE_NAMES]

[docs]def square(file_index: int, rank_index: int) -> Square: """Gets a square number by file and rank index.""" return rank_index * 8 + file_index
[docs]def square_file(square: Square) -> int: """Gets the file index of the square where ``0`` is the a-file.""" return square & 7
[docs]def square_rank(square: Square) -> int: """Gets the rank index of the square where ``0`` is the first rank.""" return square >> 3
def square_name(square: Square) -> str: """Gets the name of the square, like ``a3``.""" return SQUARE_NAMES[square]
[docs]def square_distance(a: Square, b: Square) -> int: """ Gets the distance (i.e., the number of king steps) from square *a* to *b*. """ return max(abs(square_file(a) - square_file(b)), abs(square_rank(a) - square_rank(b)))
[docs]def square_mirror(square: Square) -> Square: """Mirrors the square vertically.""" return square ^ 0x38
SQUARES_180 = [square_mirror(sq) for sq in SQUARES] Bitboard = int BB_EMPTY = 0 BB_ALL = 0xffffffffffffffff BB_SQUARES = [ BB_A1, BB_B1, BB_C1, BB_D1, BB_E1, BB_F1, BB_G1, BB_H1, BB_A2, BB_B2, BB_C2, BB_D2, BB_E2, BB_F2, BB_G2, BB_H2, BB_A3, BB_B3, BB_C3, BB_D3, BB_E3, BB_F3, BB_G3, BB_H3, BB_A4, BB_B4, BB_C4, BB_D4, BB_E4, BB_F4, BB_G4, BB_H4, BB_A5, BB_B5, BB_C5, BB_D5, BB_E5, BB_F5, BB_G5, BB_H5, BB_A6, BB_B6, BB_C6, BB_D6, BB_E6, BB_F6, BB_G6, BB_H6, BB_A7, BB_B7, BB_C7, BB_D7, BB_E7, BB_F7, BB_G7, BB_H7, BB_A8, BB_B8, BB_C8, BB_D8, BB_E8, BB_F8, BB_G8, BB_H8 ] = [1 << sq for sq in SQUARES] BB_CORNERS = BB_A1 | BB_H1 | BB_A8 | BB_H8 BB_CENTER = BB_D4 | BB_E4 | BB_D5 | BB_E5 BB_LIGHT_SQUARES = 0x55aa55aa55aa55aa BB_DARK_SQUARES = 0xaa55aa55aa55aa55 BB_FILES = [ BB_FILE_A, BB_FILE_B, BB_FILE_C, BB_FILE_D, BB_FILE_E, BB_FILE_F, BB_FILE_G, BB_FILE_H ] = [0x0101010101010101 << i for i in range(8)] BB_RANKS = [ BB_RANK_1, BB_RANK_2, BB_RANK_3, BB_RANK_4, BB_RANK_5, BB_RANK_6, BB_RANK_7, BB_RANK_8 ] = [0xff << (8 * i) for i in range(8)] BB_BACKRANKS = BB_RANK_1 | BB_RANK_8 def lsb(bb: Bitboard) -> int: return (bb & -bb).bit_length() - 1 def scan_forward(bb: Bitboard) -> Iterator[Square]: while bb: r = bb & -bb yield r.bit_length() - 1 bb ^= r def msb(bb: Bitboard) -> int: return bb.bit_length() - 1 def scan_reversed(bb: Bitboard, *, _BB_SQUARES: List[Bitboard] = BB_SQUARES) -> Iterator[Square]: while bb: r = bb.bit_length() - 1 yield r bb ^= _BB_SQUARES[r] def popcount(bb: Bitboard, *, _bin: Callable[[int], str] = bin) -> int: return _bin(bb).count("1") def flip_vertical(bb: Bitboard) -> Bitboard: # https://www.chessprogramming.org/Flipping_Mirroring_and_Rotating#FlipVertically bb = ((bb >> 8) & 0x00ff00ff00ff00ff) | ((bb & 0x00ff00ff00ff00ff) << 8) bb = ((bb >> 16) & 0x0000ffff0000ffff) | ((bb & 0x0000ffff0000ffff) << 16) bb = (bb >> 32) | ((bb & 0x00000000ffffffff) << 32) return bb def flip_horizontal(bb: Bitboard) -> Bitboard: # https://www.chessprogramming.org/Flipping_Mirroring_and_Rotating#MirrorHorizontally bb = ((bb >> 1) & 0x5555555555555555) | ((bb & 0x5555555555555555) << 1) bb = ((bb >> 2) & 0x3333333333333333) | ((bb & 0x3333333333333333) << 2) bb = ((bb >> 4) & 0x0f0f0f0f0f0f0f0f) | ((bb & 0x0f0f0f0f0f0f0f0f) << 4) return bb def flip_diagonal(bb: Bitboard) -> Bitboard: # https://www.chessprogramming.org/Flipping_Mirroring_and_Rotating#FlipabouttheDiagonal t = (bb ^ (bb << 28)) & 0x0f0f0f0f00000000 bb = bb ^ (t ^ (t >> 28)) t = (bb ^ (bb << 14)) & 0x3333000033330000 bb = bb ^ (t ^ (t >> 14)) t = (bb ^ (bb << 7)) & 0x5500550055005500 bb = bb ^ (t ^ (t >> 7)) return bb def flip_anti_diagonal(bb: Bitboard) -> Bitboard: # https://www.chessprogramming.org/Flipping_Mirroring_and_Rotating#FlipabouttheAntidiagonal t = bb ^ (bb << 36) bb = bb ^ ((t ^ (bb >> 36)) & 0xf0f0f0f00f0f0f0f) t = (bb ^ (bb << 18)) & 0xcccc0000cccc0000 bb = bb ^ (t ^ (t >> 18)) t = (bb ^ (bb << 9)) & 0xaa00aa00aa00aa00 bb = bb ^ (t ^ (t >> 9)) return bb def shift_down(b: Bitboard) -> Bitboard: return b >> 8 def shift_2_down(b: Bitboard) -> Bitboard: return b >> 16 def shift_up(b: Bitboard) -> Bitboard: return (b << 8) & BB_ALL def shift_2_up(b: Bitboard) -> Bitboard: return (b << 16) & BB_ALL def shift_right(b: Bitboard) -> Bitboard: return (b << 1) & ~BB_FILE_A & BB_ALL def shift_2_right(b: Bitboard) -> Bitboard: return (b << 2) & ~BB_FILE_A & ~BB_FILE_B & BB_ALL def shift_left(b: Bitboard) -> Bitboard: return (b >> 1) & ~BB_FILE_H def shift_2_left(b: Bitboard) -> Bitboard: return (b >> 2) & ~BB_FILE_G & ~BB_FILE_H def shift_up_left(b: Bitboard) -> Bitboard: return (b << 7) & ~BB_FILE_H & BB_ALL def shift_up_right(b: Bitboard) -> Bitboard: return (b << 9) & ~BB_FILE_A & BB_ALL def shift_down_left(b: Bitboard) -> Bitboard: return (b >> 9) & ~BB_FILE_H def shift_down_right(b: Bitboard) -> Bitboard: return (b >> 7) & ~BB_FILE_A def _sliding_attacks(square: Square, occupied: Bitboard, deltas: Iterable[int]) -> Bitboard: attacks = BB_EMPTY for delta in deltas: sq = square while True: sq += delta if not (0 <= sq < 64) or square_distance(sq, sq - delta) > 2: break attacks |= BB_SQUARES[sq] if occupied & BB_SQUARES[sq]: break return attacks def _step_attacks(square: Square, deltas: Iterable[int]) -> Bitboard: return _sliding_attacks(square, BB_ALL, deltas) BB_KNIGHT_ATTACKS = [_step_attacks(sq, [17, 15, 10, 6, -17, -15, -10, -6]) for sq in SQUARES] BB_KING_ATTACKS = [_step_attacks(sq, [9, 8, 7, 1, -9, -8, -7, -1]) for sq in SQUARES] BB_PAWN_ATTACKS = [[_step_attacks(sq, deltas) for sq in SQUARES] for deltas in [[-7, -9], [7, 9]]] def _edges(square: Square) -> Bitboard: return (((BB_RANK_1 | BB_RANK_8) & ~BB_RANKS[square_rank(square)]) | ((BB_FILE_A | BB_FILE_H) & ~BB_FILES[square_file(square)])) def _carry_rippler(mask: Bitboard) -> Iterator[Bitboard]: # Carry-Rippler trick to iterate subsets of mask. subset = BB_EMPTY while True: yield subset subset = (subset - mask) & mask if not subset: break def _attack_table(deltas: List[int]) -> Tuple[List[Bitboard], List[Dict[Bitboard, Bitboard]]]: mask_table = [] attack_table = [] for square in SQUARES: attacks = {} mask = _sliding_attacks(square, 0, deltas) & ~_edges(square) for subset in _carry_rippler(mask): attacks[subset] = _sliding_attacks(square, subset, deltas) attack_table.append(attacks) mask_table.append(mask) return mask_table, attack_table BB_DIAG_MASKS, BB_DIAG_ATTACKS = _attack_table([-9, -7, 7, 9]) BB_FILE_MASKS, BB_FILE_ATTACKS = _attack_table([-8, 8]) BB_RANK_MASKS, BB_RANK_ATTACKS = _attack_table([-1, 1]) def _rays() -> Tuple[List[List[Bitboard]], List[List[Bitboard]]]: rays = [] between = [] for a, bb_a in enumerate(BB_SQUARES): rays_row = [] between_row = [] for b, bb_b in enumerate(BB_SQUARES): if BB_DIAG_ATTACKS[a][0] & bb_b: rays_row.append((BB_DIAG_ATTACKS[a][0] & BB_DIAG_ATTACKS[b][0]) | bb_a | bb_b) between_row.append(BB_DIAG_ATTACKS[a][BB_DIAG_MASKS[a] & bb_b] & BB_DIAG_ATTACKS[b][BB_DIAG_MASKS[b] & bb_a]) elif BB_RANK_ATTACKS[a][0] & bb_b: rays_row.append(BB_RANK_ATTACKS[a][0] | bb_a) between_row.append(BB_RANK_ATTACKS[a][BB_RANK_MASKS[a] & bb_b] & BB_RANK_ATTACKS[b][BB_RANK_MASKS[b] & bb_a]) elif BB_FILE_ATTACKS[a][0] & bb_b: rays_row.append(BB_FILE_ATTACKS[a][0] | bb_a) between_row.append(BB_FILE_ATTACKS[a][BB_FILE_MASKS[a] & bb_b] & BB_FILE_ATTACKS[b][BB_FILE_MASKS[b] & bb_a]) else: rays_row.append(BB_EMPTY) between_row.append(BB_EMPTY) rays.append(rays_row) between.append(between_row) return rays, between BB_RAYS, BB_BETWEEN = _rays() SAN_REGEX = re.compile(r"^([NBKRQ])?([a-h])?([1-8])?[\-x]?([a-h][1-8])(=?[nbrqkNBRQK])?(\+|#)?\Z") FEN_CASTLING_REGEX = re.compile(r"^(?:-|[KQABCDEFGH]{0,2}[kqabcdefgh]{0,2})\Z")
[docs]class Piece: """A piece with type and color.""" def __init__(self, piece_type: PieceType, color: Color) -> None: self.piece_type = piece_type self.color = color
[docs] def symbol(self) -> str: """ Gets the symbol ``P``, ``N``, ``B``, ``R``, ``Q`` or ``K`` for white pieces or the lower-case variants for the black pieces. """ symbol = piece_symbol(self.piece_type) return symbol.upper() if self.color else symbol
[docs] def unicode_symbol(self, *, invert_color: bool = False) -> str: """ Gets the Unicode character for the piece. """ symbol = self.symbol().swapcase() if invert_color else self.symbol() return UNICODE_PIECE_SYMBOLS[symbol]
def __hash__(self) -> int: return hash(self.piece_type * (self.color + 1)) def __repr__(self) -> str: return "Piece.from_symbol({!r})".format(self.symbol()) def __str__(self) -> str: return self.symbol() def _repr_svg_(self) -> str: import chess.svg return chess.svg.piece(self, size=45) def __eq__(self, other: object) -> bool: if isinstance(other, Piece): return (self.piece_type, self.color) == (other.piece_type, other.color) else: return NotImplemented
[docs] @classmethod def from_symbol(cls, symbol: str) -> "Piece": """ Creates a :class:`~chess.Piece` instance from a piece symbol. :raises: :exc:`ValueError` if the symbol is invalid. """ return cls(PIECE_SYMBOLS.index(symbol.lower()), symbol.isupper())
[docs]class Move: """ Represents a move from a square to a square and possibly the promotion piece type. Drops and null moves are supported. """ def __init__(self, from_square: Square, to_square: Square, promotion: Optional[PieceType] = None, drop: Optional[PieceType] = None) -> None: self.from_square = from_square self.to_square = to_square self.promotion = promotion self.drop = drop
[docs] def uci(self) -> str: """ Gets an UCI string for the move. For example, a move from a7 to a8 would be ``a7a8`` or ``a7a8q`` (if the latter is a promotion to a queen). The UCI representation of a null move is ``0000``. """ if self.drop: return piece_symbol(self.drop).upper() + "@" + SQUARE_NAMES[self.to_square] elif self.promotion: return SQUARE_NAMES[self.from_square] + SQUARE_NAMES[self.to_square] + piece_symbol(self.promotion) elif self: return SQUARE_NAMES[self.from_square] + SQUARE_NAMES[self.to_square] else: return "0000"
def xboard(self) -> str: return self.uci() if self else "@@@@" def __bool__(self) -> bool: return bool(self.from_square or self.to_square or self.promotion or self.drop) def __eq__(self, other: object) -> bool: if isinstance(other, Move): return ( self.from_square == other.from_square and self.to_square == other.to_square and self.promotion == other.promotion and self.drop == other.drop) else: return NotImplemented def __repr__(self) -> str: return "Move.from_uci({!r})".format(self.uci()) def __str__(self) -> str: return self.uci() def __hash__(self) -> int: return hash((self.to_square, self.from_square, self.promotion, self.drop)) def __copy__(self) -> "Move": return type(self)(self.from_square, self.to_square, self.promotion, self.drop) def __deepcopy__(self, memo: Dict[int, object]) -> "Move": move = self.__copy__() memo[id(self)] = move return move
[docs] @classmethod def from_uci(cls, uci: str) -> "Move": """ Parses an UCI string. :raises: :exc:`ValueError` if the UCI string is invalid. """ if uci == "0000": return cls.null() elif len(uci) == 4 and "@" == uci[1]: drop = PIECE_SYMBOLS.index(uci[0].lower()) square = SQUARE_NAMES.index(uci[2:]) return cls(square, square, drop=drop) elif len(uci) == 4: return cls(SQUARE_NAMES.index(uci[0:2]), SQUARE_NAMES.index(uci[2:4])) elif len(uci) == 5: promotion = PIECE_SYMBOLS.index(uci[4]) return cls(SQUARE_NAMES.index(uci[0:2]), SQUARE_NAMES.index(uci[2:4]), promotion=promotion) else: raise ValueError("expected uci string to be of length 4 or 5: {!r}".format(uci))
[docs] @classmethod def null(cls) -> "Move": """ Gets a null move. A null move just passes the turn to the other side (and possibly forfeits en passant capturing). Null moves evaluate to ``False`` in boolean contexts. >>> import chess >>> >>> bool(chess.Move.null()) False """ return cls(0, 0)
BaseBoardT = TypeVar("BaseBoardT", bound="BaseBoard")
[docs]class BaseBoard: """ A board representing the position of chess pieces. See :class:`~chess.Board` for a full board with move generation. The board is initialized with the standard chess starting position, unless otherwise specified in the optional *board_fen* argument. If *board_fen* is ``None``, an empty board is created. """ def __init__(self, board_fen: Optional[str] = STARTING_BOARD_FEN) -> None: self.occupied_co = [BB_EMPTY, BB_EMPTY] if board_fen is None: self._clear_board() elif board_fen == STARTING_BOARD_FEN: self._reset_board() else: self._set_board_fen(board_fen) def _reset_board(self) -> None: self.pawns = BB_RANK_2 | BB_RANK_7 self.knights = BB_B1 | BB_G1 | BB_B8 | BB_G8 self.bishops = BB_C1 | BB_F1 | BB_C8 | BB_F8 self.rooks = BB_CORNERS self.queens = BB_D1 | BB_D8 self.kings = BB_E1 | BB_E8 self.promoted = BB_EMPTY self.occupied_co[WHITE] = BB_RANK_1 | BB_RANK_2 self.occupied_co[BLACK] = BB_RANK_7 | BB_RANK_8 self.occupied = BB_RANK_1 | BB_RANK_2 | BB_RANK_7 | BB_RANK_8 def reset_board(self) -> None: self._reset_board() def _clear_board(self) -> None: self.pawns = BB_EMPTY self.knights = BB_EMPTY self.bishops = BB_EMPTY self.rooks = BB_EMPTY self.queens = BB_EMPTY self.kings = BB_EMPTY self.promoted = BB_EMPTY self.occupied_co[WHITE] = BB_EMPTY self.occupied_co[BLACK] = BB_EMPTY self.occupied = BB_EMPTY
[docs] def clear_board(self) -> None: """Clears the board.""" self._clear_board()
def pieces_mask(self, piece_type: PieceType, color: Color) -> Bitboard: if piece_type == PAWN: bb = self.pawns elif piece_type == KNIGHT: bb = self.knights elif piece_type == BISHOP: bb = self.bishops elif piece_type == ROOK: bb = self.rooks elif piece_type == QUEEN: bb = self.queens elif piece_type == KING: bb = self.kings return bb & self.occupied_co[color]
[docs] def pieces(self, piece_type: PieceType, color: Color) -> "SquareSet": """ Gets pieces of the given type and color. Returns a :class:`set of squares <chess.SquareSet>`. """ return SquareSet(self.pieces_mask(piece_type, color))
[docs] def piece_at(self, square: Square) -> Optional[Piece]: """Gets the :class:`piece <chess.Piece>` at the given square.""" piece_type = self.piece_type_at(square) if piece_type: mask = BB_SQUARES[square] color = bool(self.occupied_co[WHITE] & mask) return Piece(piece_type, color) else: return None
[docs] def piece_type_at(self, square: Square) -> Optional[PieceType]: """Gets the piece type at the given square.""" mask = BB_SQUARES[square] if not self.occupied & mask: return None # Early return elif self.pawns & mask: return PAWN elif self.knights & mask: return KNIGHT elif self.bishops & mask: return BISHOP elif self.rooks & mask: return ROOK elif self.queens & mask: return QUEEN else: return KING
[docs] def king(self, color: Color) -> Optional[Square]: """ Finds the king square of the given side. Returns ``None`` if there is no king of that color. In variants with king promotions, only non-promoted kings are considered. """ king_mask = self.occupied_co[color] & self.kings & ~self.promoted return msb(king_mask) if king_mask else None
def attacks_mask(self, square: Square) -> Bitboard: bb_square = BB_SQUARES[square] if bb_square & self.pawns: color = bool(bb_square & self.occupied_co[WHITE]) return BB_PAWN_ATTACKS[color][square] elif bb_square & self.knights: return BB_KNIGHT_ATTACKS[square] elif bb_square & self.kings: return BB_KING_ATTACKS[square] else: attacks = 0 if bb_square & self.bishops or bb_square & self.queens: attacks = BB_DIAG_ATTACKS[square][BB_DIAG_MASKS[square] & self.occupied] if bb_square & self.rooks or bb_square & self.queens: attacks |= (BB_RANK_ATTACKS[square][BB_RANK_MASKS[square] & self.occupied] | BB_FILE_ATTACKS[square][BB_FILE_MASKS[square] & self.occupied]) return attacks
[docs] def attacks(self, square: Square) -> "SquareSet": """ Gets a set of attacked squares from a given square. There will be no attacks if the square is empty. Pinned pieces are still attacking other squares. Returns a :class:`set of squares <chess.SquareSet>`. """ return SquareSet(self.attacks_mask(square))
def _attackers_mask(self, color: Color, square: Square, occupied: Bitboard) -> Bitboard: rank_pieces = BB_RANK_MASKS[square] & occupied file_pieces = BB_FILE_MASKS[square] & occupied diag_pieces = BB_DIAG_MASKS[square] & occupied queens_and_rooks = self.queens | self.rooks queens_and_bishops = self.queens | self.bishops attackers = ( (BB_KING_ATTACKS[square] & self.kings) | (BB_KNIGHT_ATTACKS[square] & self.knights) | (BB_RANK_ATTACKS[square][rank_pieces] & queens_and_rooks) | (BB_FILE_ATTACKS[square][file_pieces] & queens_and_rooks) | (BB_DIAG_ATTACKS[square][diag_pieces] & queens_and_bishops) | (BB_PAWN_ATTACKS[not color][square] & self.pawns)) return attackers & self.occupied_co[color] def attackers_mask(self, color: Color, square: Square) -> Bitboard: return self._attackers_mask(color, square, self.occupied)
[docs] def is_attacked_by(self, color: Color, square: Square) -> bool: """ Checks if the given side attacks the given square. Pinned pieces still count as attackers. Pawns that can be captured en passant are **not** considered attacked. """ return bool(self.attackers_mask(color, square))
[docs] def attackers(self, color: Color, square: Square) -> "SquareSet": """ Gets a set of attackers of the given color for the given square. Pinned pieces still count as attackers. Returns a :class:`set of squares <chess.SquareSet>`. """ return SquareSet(self.attackers_mask(color, square))
def pin_mask(self, color: Color, square: Square) -> Bitboard: king = self.king(color) if king is None: return BB_ALL square_mask = BB_SQUARES[square] for attacks, sliders in [(BB_FILE_ATTACKS, self.rooks | self.queens), (BB_RANK_ATTACKS, self.rooks | self.queens), (BB_DIAG_ATTACKS, self.bishops | self.queens)]: rays = attacks[king][0] if rays & square_mask: snipers = rays & sliders & self.occupied_co[not color] for sniper in scan_reversed(snipers): if BB_BETWEEN[sniper][king] & (self.occupied | square_mask) == square_mask: return BB_RAYS[king][sniper] break return BB_ALL
[docs] def pin(self, color: Color, square: Square) -> "SquareSet": """ Detects an absolute pin (and its direction) of the given square to the king of the given color. >>> import chess >>> >>> board = chess.Board("rnb1k2r/ppp2ppp/5n2/3q4/1b1P4/2N5/PP3PPP/R1BQKBNR w KQkq - 3 7") >>> board.is_pinned(chess.WHITE, chess.C3) True >>> direction = board.pin(chess.WHITE, chess.C3) >>> direction SquareSet(0x0000000102040810) >>> print(direction) . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . 1 . . . . . . . . 1 . . . . . . . . 1 . . . . . . . . 1 . . . Returns a :class:`set of squares <chess.SquareSet>` that mask the rank, file or diagonal of the pin. If there is no pin, then a mask of the entire board is returned. """ return SquareSet(self.pin_mask(color, square))
[docs] def is_pinned(self, color: Color, square: Square) -> bool: """ Detects if the given square is pinned to the king of the given color. """ return self.pin_mask(color, square) != BB_ALL
def _remove_piece_at(self, square: Square) -> Optional[PieceType]: piece_type = self.piece_type_at(square) mask = BB_SQUARES[square] if piece_type == PAWN: self.pawns ^= mask elif piece_type == KNIGHT: self.knights ^= mask elif piece_type == BISHOP: self.bishops ^= mask elif piece_type == ROOK: self.rooks ^= mask elif piece_type == QUEEN: self.queens ^= mask elif piece_type == KING: self.kings ^= mask else: return None self.occupied ^= mask self.occupied_co[WHITE] &= ~mask self.occupied_co[BLACK] &= ~mask self.promoted &= ~mask return piece_type
[docs] def remove_piece_at(self, square: Square) -> Optional[Piece]: """ Removes the piece from the given square. Returns the :class:`~chess.Piece` or ``None`` if the square was already empty. """ color = bool(self.occupied_co[WHITE] & BB_SQUARES[square]) piece_type = self._remove_piece_at(square) return Piece(piece_type, color) if piece_type else None
def _set_piece_at(self, square: Square, piece_type: PieceType, color: Color, promoted: bool = False) -> None: self._remove_piece_at(square) mask = BB_SQUARES[square] if piece_type == PAWN: self.pawns |= mask elif piece_type == KNIGHT: self.knights |= mask elif piece_type == BISHOP: self.bishops |= mask elif piece_type == ROOK: self.rooks |= mask elif piece_type == QUEEN: self.queens |= mask elif piece_type == KING: self.kings |= mask else: return self.occupied ^= mask self.occupied_co[color] ^= mask if promoted: self.promoted ^= mask
[docs] def set_piece_at(self, square: Square, piece: Optional[Piece], promoted: bool = False) -> None: """ Sets a piece at the given square. An existing piece is replaced. Setting *piece* to ``None`` is equivalent to :func:`~chess.Board.remove_piece_at()`. """ if piece is None: self._remove_piece_at(square) else: self._set_piece_at(square, piece.piece_type, piece.color, promoted)
[docs] def board_fen(self, *, promoted: Optional[bool] = False) -> str: """ Gets the board FEN. """ builder = [] empty = 0 for square in SQUARES_180: piece = self.piece_at(square) if not piece: empty += 1 else: if empty: builder.append(str(empty)) empty = 0 builder.append(piece.symbol()) if promoted and BB_SQUARES[square] & self.promoted: builder.append("~") if BB_SQUARES[square] & BB_FILE_H: if empty: builder.append(str(empty)) empty = 0 if square != H1: builder.append("/") return "".join(builder)
def _set_board_fen(self, fen: str) -> None: # Compability with set_fen(). fen = fen.strip() if " " in fen: raise ValueError("expected position part of fen, got multiple parts: {!r}".format(fen)) # Ensure the FEN is valid. rows = fen.split("/") if len(rows) != 8: raise ValueError("expected 8 rows in position part of fen: {!r}".format(fen)) # Validate each row. for row in rows: field_sum = 0 previous_was_digit = False previous_was_piece = False for c in row: if c in ["1", "2", "3", "4", "5", "6", "7", "8"]: if previous_was_digit: raise ValueError("two subsequent digits in position part of fen: {!r}".format(fen)) field_sum += int(c) previous_was_digit = True previous_was_piece = False elif c == "~": if not previous_was_piece: raise ValueError("'~' not after piece in position part of fen: {!r}".format(fen)) previous_was_digit = False previous_was_piece = False elif c.lower() in PIECE_SYMBOLS: field_sum += 1 previous_was_digit = False previous_was_piece = True else: raise ValueError("invalid character in position part of fen: {!r}".format(fen)) if field_sum != 8: raise ValueError("expected 8 columns per row in position part of fen: {!r}".format(fen)) # Clear the board. self._clear_board() # Put pieces on the board. square_index = 0 for c in fen: if c in ["1", "2", "3", "4", "5", "6", "7", "8"]: square_index += int(c) elif c.lower() in PIECE_SYMBOLS: piece = Piece.from_symbol(c) self._set_piece_at(SQUARES_180[square_index], piece.piece_type, piece.color) square_index += 1 elif c == "~": self.promoted |= BB_SQUARES[SQUARES_180[square_index - 1]]
[docs] def set_board_fen(self, fen: str) -> None: """ Parses a FEN and sets the board from it. :raises: :exc:`ValueError` if the FEN string is invalid. """ self._set_board_fen(fen)
[docs] def piece_map(self) -> Dict[Square, Piece]: """ Gets a dictionary of :class:`pieces <chess.Piece>` by square index. """ result = {} for square in scan_reversed(self.occupied): result[square] = typing.cast(Piece, self.piece_at(square)) return result
def _set_piece_map(self, pieces: Mapping[Square, Piece]) -> None: self._clear_board() for square, piece in pieces.items(): self._set_piece_at(square, piece.piece_type, piece.color)
[docs] def set_piece_map(self, pieces: Mapping[Square, Piece]) -> None: """ Sets up the board from a dictionary of :class:`pieces <chess.Piece>` by square index. """ self._set_piece_map(pieces)
def _set_chess960_pos(self, sharnagl: int) -> None: if not 0 <= sharnagl <= 959: raise ValueError("chess960 position index not 0 <= {:d} <= 959".format(sharnagl)) # See http://www.russellcottrell.com/Chess/Chess960.htm for # a description of the algorithm. n, bw = divmod(sharnagl, 4) n, bb = divmod(n, 4) n, q = divmod(n, 6) for n1 in range(0, 4): n2 = n + (3 - n1) * (4 - n1) // 2 - 5 if n1 < n2 and 1 <= n2 <= 4: break # Bishops. bw_file = bw * 2 + 1 bb_file = bb * 2 self.bishops = (BB_FILES[bw_file] | BB_FILES[bb_file]) & BB_BACKRANKS # Queens. q_file = q q_file += int(min(bw_file, bb_file) <= q_file) q_file += int(max(bw_file, bb_file) <= q_file) self.queens = BB_FILES[q_file] & BB_BACKRANKS used = [bw_file, bb_file, q_file] # Knights. self.knights = BB_EMPTY for i in range(0, 8): if i not in used: if n1 == 0 or n2 == 0: self.knights |= BB_FILES[i] & BB_BACKRANKS used.append(i) n1 -= 1 n2 -= 1 # RKR. for i in range(0, 8): if i not in used: self.rooks = BB_FILES[i] & BB_BACKRANKS used.append(i) break for i in range(1, 8): if i not in used: self.kings = BB_FILES[i] & BB_BACKRANKS used.append(i) break for i in range(2, 8): if i not in used: self.rooks |= BB_FILES[i] & BB_BACKRANKS break # Finalize. self.pawns = BB_RANK_2 | BB_RANK_7 self.occupied_co[WHITE] = BB_RANK_1 | BB_RANK_2 self.occupied_co[BLACK] = BB_RANK_7 | BB_RANK_8 self.occupied = BB_RANK_1 | BB_RANK_2 | BB_RANK_7 | BB_RANK_8 self.promoted = BB_EMPTY
[docs] def set_chess960_pos(self, sharnagl: int) -> None: """ Sets up a Chess960 starting position given its index between 0 and 959. Also see :func:`~chess.BaseBoard.from_chess960_pos()`. """ self._set_chess960_pos(sharnagl)
[docs] def chess960_pos(self) -> Optional[int]: """ Gets the Chess960 starting position index between 0 and 959 or ``None``. """ if self.occupied_co[WHITE] != BB_RANK_1 | BB_RANK_2: return None if self.occupied_co[BLACK] != BB_RANK_7 | BB_RANK_8: return None if self.pawns != BB_RANK_2 | BB_RANK_7: return None if self.promoted: return None # Piece counts. brnqk = [self.bishops, self.rooks, self.knights, self.queens, self.kings] if [popcount(pieces) for pieces in brnqk] != [4, 4, 4, 2, 2]: return None # Symmetry. if any((BB_RANK_1 & pieces) << 56 != BB_RANK_8 & pieces for pieces in brnqk): return None # Algorithm from ChessX, src/database/bitboard.cpp, r2254. x = self.bishops & (2 + 8 + 32 + 128) if not x: return None bs1 = (lsb(x) - 1) // 2 cc_pos = bs1 x = self.bishops & (1 + 4 + 16 + 64) if not x: return None bs2 = lsb(x) * 2 cc_pos += bs2 q = 0 qf = False n0 = 0 n1 = 0 n0f = False n1f = False rf = 0 n0s = [0, 4, 7, 9] for square in range(A1, H1 + 1): bb = BB_SQUARES[square] if bb & self.queens: qf = True elif bb & self.rooks or bb & self.kings: if bb & self.kings: if rf != 1: return None else: rf += 1 if not qf: q += 1 if not n0f: n0 += 1 elif not n1f: n1 += 1 elif bb & self.knights: if not qf: q += 1 if not n0f: n0f = True elif not n1f: n1f = True if n0 < 4 and n1f and qf: cc_pos += q * 16 krn = n0s[n0] + n1 cc_pos += krn * 96 return cc_pos else: return None
def __repr__(self) -> str: return "{}({!r})".format(type(self).__name__, self.board_fen()) def __str__(self) -> str: builder = [] for square in SQUARES_180: piece = self.piece_at(square) if piece: builder.append(piece.symbol()) else: builder.append(".") if BB_SQUARES[square] & BB_FILE_H: if square != H1: builder.append("\n") else: builder.append(" ") return "".join(builder)
[docs] def unicode(self, *, invert_color: bool = False, borders: bool = False) -> str: """ Returns a string representation of the board with Unicode pieces. Useful for pretty-printing to a terminal. :param invert_color: Invert color of the Unicode pieces. :param borders: Show borders and a coordinate margin. """ builder = [] for rank_index in range(7, -1, -1): if borders: builder.append(" ") builder.append("-" * 17) builder.append("\n") builder.append(RANK_NAMES[rank_index]) builder.append(" ") for file_index in range(8): square_index = square(file_index, rank_index) if borders: builder.append("|") elif file_index > 0: builder.append(" ") piece = self.piece_at(square_index) if piece: builder.append(piece.unicode_symbol(invert_color=invert_color)) else: builder.append(u"·") if borders: builder.append("|") if borders or rank_index > 0: builder.append("\n") if borders: builder.append(" ") builder.append("-" * 17) builder.append("\n") builder.append(" a b c d e f g h") return "".join(builder)
def _repr_svg_(self) -> str: import chess.svg return chess.svg.board(board=self, size=400) def __eq__(self, board: object) -> bool: if isinstance(board, BaseBoard): return ( self.occupied == board.occupied and self.occupied_co[WHITE] == board.occupied_co[WHITE] and self.pawns == board.pawns and self.knights == board.knights and self.bishops == board.bishops and self.rooks == board.rooks and self.queens == board.queens and self.kings == board.kings) else: return NotImplemented def apply_transform(self, f: Callable[[Bitboard], Bitboard]) -> None: self.pawns = f(self.pawns) self.knights = f(self.knights) self.bishops = f(self.bishops) self.rooks = f(self.rooks) self.queens = f(self.queens) self.kings = f(self.kings) self.occupied_co[WHITE] = f(self.occupied_co[WHITE]) self.occupied_co[BLACK] = f(self.occupied_co[BLACK]) self.occupied = f(self.occupied) self.promoted = f(self.promoted) def transform(self: BaseBoardT, f: Callable[[Bitboard], Bitboard]) -> BaseBoardT: board = self.copy() board.apply_transform(f) return board
[docs] def mirror(self: BaseBoardT) -> BaseBoardT: """ Returns a mirrored copy of the board. The board is mirrored vertically and piece colors are swapped, so that the position is equivalent modulo color. """ board = self.transform(flip_vertical) board.occupied_co[WHITE], board.occupied_co[BLACK] = board.occupied_co[BLACK], board.occupied_co[WHITE] return board
[docs] def copy(self: BaseBoardT) -> BaseBoardT: """Creates a copy of the board.""" board = type(self)(None) board.pawns = self.pawns board.knights = self.knights board.bishops = self.bishops board.rooks = self.rooks board.queens = self.queens board.kings = self.kings board.occupied_co[WHITE] = self.occupied_co[WHITE] board.occupied_co[BLACK] = self.occupied_co[BLACK] board.occupied = self.occupied board.promoted = self.promoted return board
def __copy__(self: BaseBoardT) -> BaseBoardT: return self.copy() def __deepcopy__(self: BaseBoardT, memo: Dict[int, object]) -> BaseBoardT: board = self.copy() memo[id(self)] = board return board
[docs] @classmethod def empty(cls: Type[BaseBoardT]) -> BaseBoardT: """ Creates a new empty board. Also see :func:`~chess.BaseBoard.clear_board()`. """ return cls(None)
[docs] @classmethod def from_chess960_pos(cls: Type[BaseBoardT], sharnagl: int) -> BaseBoardT: """ Creates a new board, initialized with a Chess960 starting position. >>> import chess >>> import random >>> >>> board = chess.Board.from_chess960_pos(random.randint(0, 959)) """ board = cls.empty() board.set_chess960_pos(sharnagl) return board
BoardT = TypeVar("BoardT", bound="Board") class _BoardState(Generic[BoardT]): def __init__(self, board: BoardT) -> None: self.pawns = board.pawns self.knights = board.knights self.bishops = board.bishops self.rooks = board.rooks self.queens = board.queens self.kings = board.kings self.occupied_w = board.occupied_co[WHITE] self.occupied_b = board.occupied_co[BLACK] self.occupied = board.occupied self.promoted = board.promoted self.turn = board.turn self.castling_rights = board.castling_rights self.ep_square = board.ep_square self.halfmove_clock = board.halfmove_clock self.fullmove_number = board.fullmove_number def restore(self, board: BoardT) -> None: board.pawns = self.pawns board.knights = self.knights board.bishops = self.bishops board.rooks = self.rooks board.queens = self.queens board.kings = self.kings board.occupied_co[WHITE] = self.occupied_w board.occupied_co[BLACK] = self.occupied_b board.occupied = self.occupied board.promoted = self.promoted board.turn = self.turn board.castling_rights = self.castling_rights board.ep_square = self.ep_square board.halfmove_clock = self.halfmove_clock board.fullmove_number = self.fullmove_number
[docs]class Board(BaseBoard): """ A :class:`~chess.BaseBoard` and additional information representing a chess position. Provides move generation, validation, parsing, attack generation, game end detection, move counters and the capability to make and unmake moves. The board is initialized to the standard chess starting position, unless otherwise specified in the optional *fen* argument. If *fen* is ``None``, an empty board is created. Optionally supports *chess960*. In Chess960 castling moves are encoded by a king move to the corresponding rook square. Use :func:`chess.Board.from_chess960_pos()` to create a board with one of the Chess960 starting positions. It's safe to set :data:`~Board.turn`, :data:`~Board.castling_rights`, :data:`~Board.ep_square`, :data:`~Board.halfmove_clock` and :data:`~Board.fullmove_number` directly. """ aliases = ["Standard", "Chess", "Classical", "Normal"] uci_variant = "chess" # type: ClassVar[Optional[str]] xboard_variant = "normal" # type: ClassVar[Optional[str]] starting_fen = STARTING_FEN tbw_suffix = ".rtbw" # type: ClassVar[Optional[str]] tbz_suffix = ".rtbz" # type: ClassVar[Optional[str]] tbw_magic = b"\x71\xe8\x23\x5d" # type: ClassVar[Optional[bytes]] tbz_magic = b"\xd7\x66\x0c\xa5" # type: ClassVar[Optional[bytes]] pawnless_tbw_suffix = None # type: ClassVar[Optional[str]] pawnless_tbz_suffix = None # type: ClassVar[Optional[str]] pawnless_tbw_magic = None # type: ClassVar[Optional[bytes]] pawnless_tbz_magic = None # type: ClassVar[Optional[bytes]] connected_kings = False one_king = True captures_compulsory = False def __init__(self: BoardT, fen: Optional[str] = STARTING_FEN, *, chess960: bool = False) -> None: BaseBoard.__init__(self, None) self.chess960 = chess960 self.ep_square = None # type: Optional[Square] self.move_stack = [] # type: List[Move] self._stack = [] # type: List[_BoardState[BoardT]] if fen is None: self.clear() elif fen == type(self).starting_fen: self.reset() else: self.set_fen(fen) @property def pseudo_legal_moves(self) -> "PseudoLegalMoveGenerator": return PseudoLegalMoveGenerator(self) @property def legal_moves(self) -> "LegalMoveGenerator": return LegalMoveGenerator(self)
[docs] def reset(self) -> None: """Restores the starting position.""" self.turn = WHITE self.castling_rights = BB_CORNERS self.ep_square = None self.halfmove_clock = 0 self.fullmove_number = 1 self.reset_board()
def reset_board(self) -> None: super().reset_board() self.clear_stack()
[docs] def clear(self) -> None: """ Clears the board. Resets move stack and move counters. The side to move is white. There are no rooks or kings, so castling rights are removed. In order to be in a valid :func:`~chess.Board.status()` at least kings need to be put on the board. """ self.turn = WHITE self.castling_rights = BB_EMPTY self.ep_square = None self.halfmove_clock = 0 self.fullmove_number = 1 self.clear_board()
[docs] def clear_board(self) -> None: super().clear_board() self.clear_stack()
[docs] def clear_stack(self) -> None: """Clears the move stack.""" del self.move_stack[:] del self._stack[:]
[docs] def root(self: BoardT) -> BoardT: """Returns a copy of the root position.""" if self._stack: board = type(self)(None, chess960=self.chess960) self._stack[0].restore(board) return board else: return self.copy(stack=False)
[docs] def remove_piece_at(self, square: Square) -> Optional[Piece]: piece = super().remove_piece_at(square) self.clear_stack() return piece
[docs] def set_piece_at(self, square: Square, piece: Optional[Piece], promoted: bool = False) -> None: super().set_piece_at(square, piece, promoted=promoted) self.clear_stack()
def generate_pseudo_legal_moves(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: our_pieces = self.occupied_co[self.turn] # Generate piece moves. non_pawns = our_pieces & ~self.pawns & from_mask for from_square in scan_reversed(non_pawns): moves = self.attacks_mask(from_square) & ~our_pieces & to_mask for to_square in scan_reversed(moves): yield Move(from_square, to_square) # Generate castling moves. if from_mask & self.kings: yield from self.generate_castling_moves(from_mask, to_mask) # The remaining moves are all pawn moves. pawns = self.pawns & self.occupied_co[self.turn] & from_mask if not pawns: return # Generate pawn captures. capturers = pawns for from_square in scan_reversed(capturers): targets = ( BB_PAWN_ATTACKS[self.turn][from_square] & self.occupied_co[not self.turn] & to_mask) for to_square in scan_reversed(targets): if square_rank(to_square) in [0, 7]: yield Move(from_square, to_square, QUEEN) yield Move(from_square, to_square, ROOK) yield Move(from_square, to_square, BISHOP) yield Move(from_square, to_square, KNIGHT) else: yield Move(from_square, to_square) # Prepare pawn advance generation. if self.turn == WHITE: single_moves = pawns << 8 & ~self.occupied double_moves = single_moves << 8 & ~self.occupied & (BB_RANK_3 | BB_RANK_4) else: single_moves = pawns >> 8 & ~self.occupied double_moves = single_moves >> 8 & ~self.occupied & (BB_RANK_6 | BB_RANK_5) single_moves &= to_mask double_moves &= to_mask # Generate single pawn moves. for to_square in scan_reversed(single_moves): from_square = to_square + (8 if self.turn == BLACK else -8) if square_rank(to_square) in [0, 7]: yield Move(from_square, to_square, QUEEN) yield Move(from_square, to_square, ROOK) yield Move(from_square, to_square, BISHOP) yield Move(from_square, to_square, KNIGHT) else: yield Move(from_square, to_square) # Generate double pawn moves. for to_square in scan_reversed(double_moves): from_square = to_square + (16 if self.turn == BLACK else -16) yield Move(from_square, to_square) # Generate en passant captures. if self.ep_square: yield from self.generate_pseudo_legal_ep(from_mask, to_mask) def generate_pseudo_legal_ep(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: if not self.ep_square or not BB_SQUARES[self.ep_square] & to_mask: return if BB_SQUARES[self.ep_square] & self.occupied: return capturers = ( self.pawns & self.occupied_co[self.turn] & from_mask & BB_PAWN_ATTACKS[not self.turn][self.ep_square] & BB_RANKS[4 if self.turn else 3]) for capturer in scan_reversed(capturers): yield Move(capturer, self.ep_square) def generate_pseudo_legal_captures(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: return itertools.chain( self.generate_pseudo_legal_moves(from_mask, to_mask & self.occupied_co[not self.turn]), self.generate_pseudo_legal_ep(from_mask, to_mask))
[docs] def is_check(self) -> bool: """Returns if the current side to move is in check.""" king = self.king(self.turn) return king is not None and self.is_attacked_by(not self.turn, king)
[docs] def is_into_check(self, move: Move) -> bool: """ Checks if the given move would leave the king in check or put it into check. The move must be at least pseudo legal. """ king = self.king(self.turn) if king is None: return False checkers = self.attackers_mask(not self.turn, king) if checkers: # If already in check, look if it is an evasion. if move not in self._generate_evasions(king, checkers, BB_SQUARES[move.from_square], BB_SQUARES[move.to_square]): return True return not self._is_safe(king, self._slider_blockers(king), move)
[docs] def was_into_check(self) -> bool: """ Checks if the king of the other side is attacked. Such a position is not valid and could only be reached by an illegal move. """ king = self.king(not self.turn) return king is not None and self.is_attacked_by(self.turn, king)
def is_pseudo_legal(self, move: Move) -> bool: # Null moves are not pseudo legal. if not move: return False # Drops are not pseudo legal. if move.drop: return False # Source square must not be vacant. piece = self.piece_type_at(move.from_square) if not piece: return False # Get square masks. from_mask = BB_SQUARES[move.from_square] to_mask = BB_SQUARES[move.to_square] # Check turn. if not self.occupied_co[self.turn] & from_mask: return False # Only pawns can promote and only on the back rank. if move.promotion: if piece != PAWN: return False if self.turn == WHITE and square_rank(move.to_square) != 7: return False elif self.turn == BLACK and square_rank(move.to_square) != 0: return False # Handle castling. if piece == KING: if move in self.generate_castling_moves(): return True # Destination square can not be occupied. if self.occupied_co[self.turn] & to_mask: return False # Handle pawn moves. if piece == PAWN: return move in self.generate_pseudo_legal_moves(from_mask, to_mask) # Handle all other pieces. return bool(self.attacks_mask(move.from_square) & to_mask) def is_legal(self, move: Move) -> bool: return not self.is_variant_end() and self.is_pseudo_legal(move) and not self.is_into_check(move)
[docs] def is_variant_end(self) -> bool: """ Checks if the game is over due to a special variant end condition. Note, for example, that stalemate is not considered a variant-specific end condition (this method will return ``False``), yet it can have a special **result** in suicide chess (any of :func:`~chess.Board.is_variant_loss()`, :func:`~chess.Board.is_variant_win()`, :func:`~chess.Board.is_variant_draw()` might return ``True``). """ return False
[docs] def is_variant_loss(self) -> bool: """Checks if a special variant-specific loss condition is fulfilled.""" return False
[docs] def is_variant_win(self) -> bool: """Checks if a special variant-specific win condition is fulfilled.""" return False
[docs] def is_variant_draw(self) -> bool: """ Checks if a special variant-specific drawing condition is fulfilled. """ return False
[docs] def is_game_over(self, *, claim_draw: bool = False) -> bool: """ Checks if the game is over due to :func:`checkmate <chess.Board.is_checkmate()>`, :func:`stalemate <chess.Board.is_stalemate()>`, :func:`insufficient material <chess.Board.is_insufficient_material()>`, the :func:`seventyfive-move rule <chess.Board.is_seventyfive_moves()>`, :func:`fivefold repetition <chess.Board.is_fivefold_repetition()>` or a :func:`variant end condition <chess.Board.is_variant_end()>`. The game is not considered to be over by the :func:`fifty-move rule <chess.Board.can_claim_fifty_moves()>` or :func:`threefold repetition <chess.Board.can_claim_threefold_repetition()>`, unless *claim_draw* is given. Note that checking the latter can be slow. """ # Seventyfive-move rule. if self.is_seventyfive_moves(): return True # Insufficient material. if self.is_insufficient_material(): return True # Stalemate or checkmate. if not any(self.generate_legal_moves()): return True # Fivefold repetition. if self.is_fivefold_repetition(): return True # Claim draw. if claim_draw and self.can_claim_draw(): return True return False
[docs] def result(self, *, claim_draw: bool = False) -> str: """ Gets the game result. ``1-0``, ``0-1`` or ``1/2-1/2`` if the :func:`game is over <chess.Board.is_game_over()>`. Otherwise, the result is undetermined: ``*``. """ # Chess variant support. if self.is_variant_loss(): return "0-1" if self.turn == WHITE else "1-0" elif self.is_variant_win(): return "1-0" if self.turn == WHITE else "0-1" elif self.is_variant_draw(): return "1/2-1/2" # Checkmate. if self.is_checkmate(): return "0-1" if self.turn == WHITE else "1-0" # Draw claimed. if claim_draw and self.can_claim_draw(): return "1/2-1/2" # Seventyfive-move rule or fivefold repetition. if self.is_seventyfive_moves() or self.is_fivefold_repetition(): return "1/2-1/2" # Insufficient material. if self.is_insufficient_material(): return "1/2-1/2" # Stalemate. if not any(self.generate_legal_moves()): return "1/2-1/2" # Undetermined. return "*"
[docs] def is_checkmate(self) -> bool: """Checks if the current position is a checkmate.""" if not self.is_check(): return False return not any(self.generate_legal_moves())
[docs] def is_stalemate(self) -> bool: """Checks if the current position is a stalemate.""" if self.is_check(): return False if self.is_variant_end(): return False return not any(self.generate_legal_moves())
[docs] def is_insufficient_material(self) -> bool: """ Checks if neither side has sufficient winning material (:func:`~chess.Board.has_insufficient_material()`). """ return all(self.has_insufficient_material(color) for color in COLORS)
[docs] def has_insufficient_material(self, color: Color) -> bool: """ Checks if *color* has insufficient winning material. This is guaranteed to return ``False`` if *color* can still win the game. The converse does not necessarily hold: The implementation only looks at the material, including the colors of bishops, but not considering piece positions. So fortress positions or positions with forced lines may return ``False``, even though there is no possible winning line. """ if self.occupied_co[color] & (self.pawns | self.rooks | self.queens): return False # Knights are only insufficient material if: # (1) We do not have any other pieces, including more than one knight. # (2) The opponent does not have pawns, knights, bishops or rooks. # These would allow self mate. if self.occupied_co[color] & self.knights: return (popcount(self.occupied_co[color]) <= 2 and not (self.occupied_co[not color] & ~self.kings & ~self.queens)) # Bishops are only insufficient material if: # (1) We no dot have any other pieces, including bishops of the # opposite color. # (2) The opponent does not have bishops of the opposite color, # pawns or knights. These would allow self mate. if self.occupied_co[color] & self.bishops: same_color = (not self.bishops & BB_DARK_SQUARES) or (not self.bishops & BB_LIGHT_SQUARES) return same_color and not (self.occupied_co[not color] & ~self.kings & ~self.rooks & ~self.queens) return True
[docs] def is_seventyfive_moves(self) -> bool: """ Since the 1st of July 2014, a game is automatically drawn (without a claim by one of the players) if the half-move clock since a capture or pawn move is equal to or grather than 150. Other means to end a game take precedence. """ if self.halfmove_clock >= 150: if any(self.generate_legal_moves()): return True return False
[docs] def is_fivefold_repetition(self) -> bool: """ Since the 1st of July 2014 a game is automatically drawn (without a claim by one of the players) if a position occurs for the fifth time. Originally this had to occur on consecutive alternating moves, but this has since been revised. """ transposition_key = self._transposition_key() repetitions = 1 switchyard = [] while self.move_stack and repetitions < 5: move = self.pop() switchyard.append(move) if self.is_irreversible(move): break if self._transposition_key() == transposition_key: repetitions += 1 while switchyard: self.push(switchyard.pop()) return repetitions >= 5
[docs] def can_claim_draw(self) -> bool: """ Checks if the side to move can claim a draw by the fifty-move rule or by threefold repetition. Note that checking the latter can be slow. """ return self.can_claim_fifty_moves() or self.can_claim_threefold_repetition()
[docs] def can_claim_fifty_moves(self) -> bool: """ Draw by the fifty-move rule can be claimed once the clock of halfmoves since the last capture or pawn move becomes equal or greater to 100 and the side to move still has a legal move they can make. """ # Fifty-move rule. if self.halfmove_clock >= 100: if any(self.generate_legal_moves()): return True return False
[docs] def can_claim_threefold_repetition(self) -> bool: """ Draw by threefold repetition can be claimed if the position on the board occured for the third time or if such a repetition is reached with one of the possible legal moves. Note that checking this can be slow: In the worst case scenario every legal move has to be tested and the entire game has to be replayed because there is no incremental transposition table. """ transposition_key = self._transposition_key() transpositions = collections.Counter() # type: typing.Counter[Hashable] transpositions.update((transposition_key, )) # Count positions. switchyard = [] while self.move_stack: move = self.pop() switchyard.append(move) if self.is_irreversible(move): break transpositions.update((self._transposition_key(), )) while switchyard: self.push(switchyard.pop()) # Threefold repetition occured. if transpositions[transposition_key] >= 3: return True # The next legal move is a threefold repetition. for move in self.generate_legal_moves(): self.push(move) try: if transpositions[self._transposition_key()] >= 2: return True finally: self.pop() return False
[docs] def is_repetition(self, count: int = 3) -> bool: """ Checks if the current position has repeated 3 (or a given number of) times. Unlike :func:`~chess.Board.can_claim_threefold_repetition()`, this does not consider a repetition that can be played on the next move. Note that checking this can be slow: In the worst case the entire game has to be replayed because there is no incremental transposition table. """ transposition_key = self._transposition_key() switchyard = [] try: while True: if count <= 1: return True if not self.move_stack: break move = self.pop() switchyard.append(move) if self.is_irreversible(move): break if self._transposition_key() == transposition_key: count -= 1 finally: while switchyard: self.push(switchyard.pop()) return False
def _board_state(self: BoardT) -> _BoardState[BoardT]: return _BoardState(self) def _push_capture(self, move: Move, capture_square: Square, piece_type: PieceType, was_promoted: bool) -> None: pass
[docs] def push(self: BoardT, move: Move) -> None: """ Updates the position with the given move and puts it onto the move stack. >>> import chess >>> >>> board = chess.Board() >>> >>> Nf3 = chess.Move.from_uci("g1f3") >>> board.push(Nf3) # Make the move >>> board.pop() # Unmake the last move Move.from_uci('g1f3') Null moves just increment the move counters, switch turns and forfeit en passant capturing. :warning: Moves are not checked for legality. """ # Push move and remember board state. move = self._to_chess960(move) self.move_stack.append(self._from_chess960(self.chess960, move.from_square, move.to_square, move.promotion, move.drop)) self._stack.append(self._board_state()) # Reset en passant square. ep_square = self.ep_square self.ep_square = None # Increment move counters. self.halfmove_clock += 1 if self.turn == BLACK: self.fullmove_number += 1 # On a null move, simply swap turns and reset the en passant square. if not move: self.turn = not self.turn return # Drops. if move.drop: self._set_piece_at(move.to_square, move.drop, self.turn) self.turn = not self.turn return # Zero the half-move clock. if self.is_zeroing(move): self.halfmove_clock = 0 from_bb = BB_SQUARES[move.from_square] to_bb = BB_SQUARES[move.to_square] promoted = bool(self.promoted & from_bb) piece_type = self._remove_piece_at(move.from_square) assert piece_type is not None, "push() expects move to be pseudo-legal, but got {} in {}".format(move, self.fen()) capture_square = move.to_square captured_piece_type = self.piece_type_at(capture_square) # Update castling rights. self.castling_rights = self.clean_castling_rights() & ~to_bb & ~from_bb if piece_type == KING and not promoted: if self.turn == WHITE: self.castling_rights &= ~BB_RANK_1 else: self.castling_rights &= ~BB_RANK_8 elif captured_piece_type == KING and not self.promoted & to_bb: if self.turn == WHITE and square_rank(move.to_square) == 7: self.castling_rights &= ~BB_RANK_8 elif self.turn == BLACK and square_rank(move.to_square) == 0: self.castling_rights &= ~BB_RANK_1 # Handle special pawn moves. if piece_type == PAWN: diff = move.to_square - move.from_square if diff == 16 and square_rank(move.from_square) == 1: self.ep_square = move.from_square + 8 elif diff == -16 and square_rank(move.from_square) == 6: self.ep_square = move.from_square - 8 elif move.to_square == ep_square and abs(diff) in [7, 9] and not captured_piece_type: # Remove pawns captured en passant. down = -8 if self.turn == WHITE else 8 capture_square = ep_square + down captured_piece_type = self._remove_piece_at(capture_square) # Promotion. if move.promotion: promoted = True piece_type = move.promotion # Castling. castling = piece_type == KING and self.occupied_co[self.turn] & to_bb if castling: a_side = square_file(move.to_square) < square_file(move.from_square) self._remove_piece_at(move.from_square) self._remove_piece_at(move.to_square) if a_side: self._set_piece_at(C1 if self.turn == WHITE else C8, KING, self.turn) self._set_piece_at(D1 if self.turn == WHITE else D8, ROOK, self.turn) else: self._set_piece_at(G1 if self.turn == WHITE else G8, KING, self.turn) self._set_piece_at(F1 if self.turn == WHITE else F8, ROOK, self.turn) # Put the piece on the target square. if not castling: was_promoted = bool(self.promoted & to_bb) self._set_piece_at(move.to_square, piece_type, self.turn, promoted) if captured_piece_type: self._push_capture(move, capture_square, captured_piece_type, was_promoted) # Swap turn. self.turn = not self.turn
[docs] def pop(self: BoardT) -> Move: """ Restores the previous position and returns the last move from the stack. :raises: :exc:`IndexError` if the stack is empty. """ move = self.move_stack.pop() self._stack.pop().restore(self) return move
[docs] def peek(self) -> Move: """ Gets the last move from the move stack. :raises: :exc:`IndexError` if the move stack is empty. """ return self.move_stack[-1]
def castling_shredder_fen(self) -> str: castling_rights = self.clean_castling_rights() if not castling_rights: return "-" builder = [] for square in scan_reversed(castling_rights & BB_RANK_1): builder.append(FILE_NAMES[square_file(square)].upper()) for square in scan_reversed(castling_rights & BB_RANK_8): builder.append(FILE_NAMES[square_file(square)]) return "".join(builder) def castling_xfen(self) -> str: builder = [] for color in COLORS: king = self.king(color) if king is None: continue king_file = square_file(king) backrank = BB_RANK_1 if color == WHITE else BB_RANK_8 for rook_square in scan_reversed(self.clean_castling_rights() & backrank): rook_file = square_file(rook_square) a_side = rook_file < king_file other_rooks = self.occupied_co[color] & self.rooks & backrank & ~BB_SQUARES[rook_square] if any((square_file(other) < rook_file) == a_side for other in scan_reversed(other_rooks)): ch = FILE_NAMES[rook_file] else: ch = "q" if a_side else "k" builder.append(ch.upper() if color == WHITE else ch) if builder: return "".join(builder) else: return "-"
[docs] def fen(self, *, shredder: bool = False, en_passant: str = "legal", promoted: Optional[bool] = None) -> str: """ Gets a FEN representation of the position. A FEN string (e.g., ``rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1``) consists of the position part :func:`~chess.Board.board_fen()`, the :data:`~chess.Board.turn`, the castling part (:data:`~chess.Board.castling_rights`), the en passant square (:data:`~chess.Board.ep_square`), the :data:`~chess.Board.halfmove_clock` and the :data:`~chess.Board.fullmove_number`. :param shredder: Use :func:`~chess.Board.castling_shredder_fen()` and encode castling rights by the file of the rook (like ``HAha``) instead of the default :func:`~chess.Board.castling_xfen()` (like ``KQkq``). :param en_passant: By default, only fully legal en passant squares are included (:func:`~chess.Board.has_legal_en_passant()`). Pass ``fen`` to strictly follow the FEN specification (always include the en passant square after a two-step pawn move) or ``xfen`` to follow the X-FEN specification (:func:`~chess.Board.has_pseudo_legal_en_passant()`). :param promoted: Mark promoted pieces like ``Q~``. By default, this is only enabled in chess variants where this is relevant. """ return " ".join([ self.epd(shredder=shredder, en_passant=en_passant, promoted=promoted), str(self.halfmove_clock), str(self.fullmove_number) ])
def shredder_fen(self, *, en_passant: str = "legal", promoted: Optional[bool] = None) -> str: return " ".join([ self.epd(shredder=True, en_passant=en_passant, promoted=promoted), str(self.halfmove_clock), str(self.fullmove_number) ])
[docs] def set_fen(self, fen: str) -> None: """ Parses a FEN and sets the position from it. :raises: :exc:`ValueError` if the FEN string is invalid. """ parts = fen.split() # Board part. try: board_part = parts.pop(0) except IndexError: raise ValueError("empty fen") # Turn. try: turn_part = parts.pop(0) except IndexError: turn = WHITE else: if turn_part == "w": turn = WHITE elif turn_part == "b": turn = BLACK else: raise ValueError("expected 'w' or 'b' for turn part of fen: {!r}".format(fen)) # Validate castling part. try: castling_part = parts.pop(0) except IndexError: castling_part = "-" else: if not FEN_CASTLING_REGEX.match(castling_part): raise ValueError("invalid castling part in fen: {!r}".format(fen)) # En passant square. try: ep_part = parts.pop(0) except IndexError: ep_square = None else: try: ep_square = None if ep_part == "-" else SQUARE_NAMES.index(ep_part) except ValueError: raise ValueError("invalid en passant part in fen: {!r}".format(fen)) # Check that the half-move part is valid. try: halfmove_part = parts.pop(0) except IndexError: halfmove_clock = 0 else: try: halfmove_clock = int(halfmove_part) except ValueError: raise ValueError("invalid half-move clock in fen: {!r}".format(fen)) if halfmove_clock < 0: raise ValueError("half-move clock cannot be negative: {!r}".format(fen)) # Check that the full-move number part is valid. # 0 is allowed for compability, but later replaced with 1. try: fullmove_part = parts.pop(0) except IndexError: fullmove_number = 1 else: try: fullmove_number = int(fullmove_part) except ValueError: raise ValueError("invalid fullmove number in fen: {!r}".format(fen)) if fullmove_number < 0: raise ValueError("fullmove number cannot be negative: {!r}".format(fen)) fullmove_number = max(fullmove_number, 1) # All parts should be consumed now. if parts: raise ValueError("fen string has more parts than expected: {!r}".format(fen)) # Validate the board part and set it. self._set_board_fen(board_part) # Apply. self.turn = turn self._set_castling_fen(castling_part) self.ep_square = ep_square self.halfmove_clock = halfmove_clock self.fullmove_number = fullmove_number self.clear_stack()
def _set_castling_fen(self, castling_fen: str) -> None: if not castling_fen or castling_fen == "-": self.castling_rights = BB_EMPTY return if not FEN_CASTLING_REGEX.match(castling_fen): raise ValueError("invalid castling fen: {!r}".format(castling_fen)) self.castling_rights = BB_EMPTY for flag in castling_fen: color = WHITE if flag.isupper() else BLACK flag = flag.lower() backrank = BB_RANK_1 if color == WHITE else BB_RANK_8 rooks = self.occupied_co[color] & self.rooks & backrank king = self.king(color) if flag == "q": # Select the leftmost rook. if king is not None and lsb(rooks) < king: self.castling_rights |= rooks & -rooks else: self.castling_rights |= BB_FILE_A & backrank elif flag == "k": # Select the rightmost rook. rook = msb(rooks) if king is not None and king < rook: self.castling_rights |= BB_SQUARES[rook] else: self.castling_rights |= BB_FILE_H & backrank else: self.castling_rights |= BB_FILES[FILE_NAMES.index(flag)] & backrank
[docs] def set_castling_fen(self, castling_fen: str) -> None: """ Sets castling rights from a string in FEN notation like ``Qqk``. :raises: :exc:`ValueError` if the castling FEN is syntactically invalid. """ self._set_castling_fen(castling_fen) self.clear_stack()
[docs] def set_board_fen(self, fen: str) -> None: super().set_board_fen(fen) self.clear_stack()
[docs] def set_piece_map(self, pieces: Mapping[Square, Piece]) -> None: super().set_piece_map(pieces) self.clear_stack()
[docs] def set_chess960_pos(self, sharnagl: int) -> None: super().set_chess960_pos(sharnagl) self.chess960 = True self.turn = WHITE self.castling_rights = self.rooks self.ep_square = None self.halfmove_clock = 0 self.fullmove_number = 1 self.clear_stack()
[docs] def chess960_pos(self, *, ignore_turn: bool = False, ignore_castling: bool = False, ignore_counters: bool = True) -> Optional[int]: """ Gets the Chess960 starting position index between 0 and 956 or ``None`` if the current position is not a Chess960 starting position. By default white to move (**ignore_turn**) and full castling rights (**ignore_castling**) are required, but move counters (**ignore_counters**) are ignored. """ if self.ep_square: return None if not ignore_turn: if self.turn != WHITE: return None if not ignore_castling: if self.clean_castling_rights() != self.rooks: return None if not ignore_counters: if self.fullmove_number != 1 or self.halfmove_clock != 0: return None return super().chess960_pos()
def _epd_operations(self, operations: Mapping[str, Union[None, str, int, float, Move, Iterable[Move]]]) -> str: epd = [] first_op = True for opcode, operand in operations.items(): if not first_op: epd.append(" ") first_op = False epd.append(opcode) # Value is empty. if operand is None: epd.append(";") continue # Value is a move. if isinstance(operand, Move): # Append SAN for moves. epd.append(" ") epd.append(self.san(operand)) epd.append(";") continue # Value is numeric. if isinstance(operand, (int, float)): # Append integer or float. epd.append(" ") epd.append(str(operand)) epd.append(";") continue # Value is a set of moves or a variation. if hasattr(operand, "__iter__"): position = Board(self.shredder_fen()) if opcode == "pv" else self iterator = operand.__iter__() first_move = next(iterator) if isinstance(first_move, Move): epd.append(" ") epd.append(position.san(first_move)) if opcode == "pv": position.push(first_move) for move in iterator: assert isinstance(move, Move), "expected homogeneous list of moves, got: {}, ..., {!r}".format(first_move, move) epd.append(" ") epd.append(position.san(move)) if opcode == "pv": position.push(move) epd.append(";") continue # Append as escaped string. epd.append(" \"") epd.append(str(operand).replace("\r", "").replace("\n", " ").replace("\\", "\\\\").replace("\"", "\\\"")) epd.append("\";") return "".join(epd)
[docs] def epd(self, *, shredder: bool = False, en_passant: str = "legal", promoted: Optional[bool] = None, **operations: Union[None, str, int, float, Move, Iterable[Move]]) -> str: """ Gets an EPD representation of the current position. See :func:`~chess.Board.fen()` for FEN formatting options (*shredder*, *ep_square* and *promoted*). EPD operations can be given as keyword arguments. Supported operands are strings, integers, floats, moves, lists of moves and ``None``. All other operands are converted to strings. A list of moves for *pv* will be interpreted as a variation. All other move lists are interpreted as a set of moves in the current position. *hmvc* and *fmvc* are not included by default. You can use: >>> import chess >>> >>> board = chess.Board() >>> board.epd(hmvc=board.halfmove_clock, fmvc=board.fullmove_number) 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - hmvc 0; fmvc 1;' """ if en_passant == "fen": ep_square = self.ep_square elif en_passant == "xfen": ep_square = self.ep_square if self.has_pseudo_legal_en_passant() else None else: ep_square = self.ep_square if self.has_legal_en_passant() else None epd = [self.board_fen(promoted=promoted), "w" if self.turn == WHITE else "b", self.castling_shredder_fen() if shredder else self.castling_xfen(), SQUARE_NAMES[ep_square] if ep_square is not None else "-"] if operations: epd.append(self._epd_operations(operations)) return " ".join(epd)
def _parse_epd_ops(self: BoardT, operation_part: str, make_board: Callable[[], BoardT]) -> Dict[str, Union[None, str, int, float, Move, List[Move]]]: operations = {} # type: Dict[str, Union[None, str, int, float, Move, List[Move]]] state = "opcode" opcode = "" operand = "" position = None for ch in itertools.chain(operation_part, [None]): if state == "opcode": if ch == " ": if opcode: state = "after_opcode" elif ch is None or ch == ";": if opcode: operations[opcode] = None opcode = "" else: opcode += ch elif state == "after_opcode": if ch == " ": pass elif ch == "\"": state = "string" elif ch is None or ch == ";": if opcode: operations[opcode] = None opcode = "" state = "opcode" elif ch in "+-.0123456789": operand = ch state = "numeric" else: operand = ch state = "san" elif state == "numeric": if ch is None or ch == ";": operations[opcode] = float(operand) try: operations[opcode] = int(operand) except ValueError: pass opcode = "" operand = "" state = "opcode" else: operand += ch elif state == "string": if ch is None or ch == "\"": operations[opcode] = operand opcode = "" operand = "" state = "opcode" elif ch == "\\": state = "string_escape" else: operand += ch elif state == "string_escape": if ch is None: operations[opcode] = operand opcode = "" operand = "" state = "opcode" else: operand += ch state = "string" elif state == "san": if ch is None or ch == ";": if position is None: position = make_board() if opcode == "pv": # A variation. variation = [] for token in operand.split(): move = position.parse_xboard(token) variation.append(move) position.push(move) # Reset the position. while position.move_stack: position.pop() operations[opcode] = variation elif opcode in ["bm", "am"]: # A set of moves. operations[opcode] = [position.parse_xboard(token) for token in operand.split()] else: # A single move. operations[opcode] = position.parse_xboard(operand) opcode = "" operand = "" state = "opcode" else: operand += ch assert state == "opcode" return operations
[docs] def set_epd(self, epd: str) -> Dict[str, Union[None, str, int, float, Move, List[Move]]]: """ Parses the given EPD string and uses it to set the position. If present, ``hmvc`` and ``fmvn`` are used to set the half-move clock and the full-move number. Otherwise, ``0`` and ``1`` are used. Returns a dictionary of parsed operations. Values can be strings, integers, floats, move objects, or lists of moves. :raises: :exc:`ValueError` if the EPD string is invalid. """ parts = epd.strip().rstrip(";").split(None, 4) # Parse ops. if len(parts) > 4: operations = self._parse_epd_ops(parts.pop(), lambda: type(self)(" ".join(parts) + " 0 1")) parts.append(str(operations["hmvc"]) if "hmvc" in operations else "0") parts.append(str(operations["fmvn"]) if "fmvn" in operations else "1") self.set_fen(" ".join(parts)) return operations else: self.set_fen(epd) return {}
[docs] def san(self, move: Move) -> str: """ Gets the standard algebraic notation of the given move in the context of the current position. """ return self._algebraic(move)
[docs] def lan(self, move: Move) -> str: """ Gets the long algebraic notation of the given move in the context of the current position. """ return self._algebraic(move, long=True)
def _algebraic(self, move: Move, long: bool = False) -> str: if not move: # Null move. return "--" # Look ahead for check or checkmate. self.push(move) is_check = self.is_check() is_checkmate = (is_check and self.is_checkmate()) or self.is_variant_loss() or self.is_variant_win() self.pop() # Drops. if move.drop: san = "" if move.drop != PAWN: san = piece_symbol(move.drop).upper() san += "@" + SQUARE_NAMES[move.to_square] # Castling. if self.is_castling(move): if square_file(move.to_square) < square_file(move.from_square): san = "O-O-O" else: san = "O-O" if move.drop or self.is_castling(move): if is_checkmate: return san + "#" elif is_check: return san + "+" else: return san piece_type = self.piece_type_at(move.from_square) assert piece_type, "san() and lan() expect move to be legal or null, but got {} in {}".format(move, self.fen()) capture = self.is_capture(move) if piece_type == PAWN: san = "" else: san = piece_symbol(piece_type).upper() if long: san += SQUARE_NAMES[move.from_square] elif piece_type != PAWN: # Get ambiguous move candidates. # Relevant candidates: not exactly the current move, # but to the same square. others = 0 from_mask = self.pieces_mask(piece_type, self.turn) from_mask &= ~BB_SQUARES[move.from_square] to_mask = BB_SQUARES[move.to_square] for candidate in self.generate_legal_moves(from_mask, to_mask): others |= BB_SQUARES[candidate.from_square] # Disambiguate. if others: row, column = False, False if others & BB_RANKS[square_rank(move.from_square)]: column = True if others & BB_FILES[square_file(move.from_square)]: row = True else: column = True if column: san += FILE_NAMES[square_file(move.from_square)] if row: san += RANK_NAMES[square_rank(move.from_square)] elif capture: san += FILE_NAMES[square_file(move.from_square)] # Captures. if capture: san += "x" elif long: san += "-" # Destination square. san += SQUARE_NAMES[move.to_square] # Promotion. if move.promotion: san += "=" + piece_symbol(move.promotion).upper() # Add check or checkmate suffix. if is_checkmate: san += "#" elif is_check: san += "+" return san
[docs] def variation_san(self, variation: Iterable[Move]) -> str: """ Given a sequence of moves, returns a string representing the sequence in standard algebraic notation (e.g., ``1. e4 e5 2. Nf3 Nc6`` or ``37...Bg6 38. fxg6``). The board will not be modified as a result of calling this. :raises: :exc:`ValueError` if any moves in the sequence are illegal. """ board = self.copy(stack=False) san = [] for move in variation: if not board.is_legal(move): raise ValueError("illegal move {} in position {}".format(move, board.fen())) if board.turn == WHITE: san.append("{}. {}".format(board.fullmove_number, board.san(move))) elif not san: san.append("{}...{}".format(board.fullmove_number, board.san(move))) else: san.append(board.san(move)) board.push(move) return " ".join(san)
[docs] def parse_san(self, san: str) -> Move: """ Uses the current position as the context to parse a move in standard algebraic notation and returns the corresponding move object. The returned move is guaranteed to be either legal or a null move. :raises: :exc:`ValueError` if the SAN is invalid or ambiguous. """ # Castling. try: if san in ["O-O", "O-O+", "O-O#"]: return next(move for move in self.generate_castling_moves() if self.is_kingside_castling(move)) elif san in ["O-O-O", "O-O-O+", "O-O-O#"]: return next(move for move in self.generate_castling_moves() if self.is_queenside_castling(move)) except StopIteration: raise ValueError("illegal san: {!r} in {}".format(san, self.fen())) # Match normal moves. match = SAN_REGEX.match(san) if not match: # Null moves. if san in ["--", "Z0"]: return Move.null() raise ValueError("invalid san: {!r}".format(san)) # Get target square. to_square = SQUARE_NAMES.index(match.group(4)) to_mask = BB_SQUARES[to_square] # Get the promotion type. p = match.group(5) promotion = p and PIECE_SYMBOLS.index(p[-1].lower()) # Filter by piece type. if match.group(1): piece_type = PIECE_SYMBOLS.index(match.group(1).lower()) from_mask = self.pieces_mask(piece_type, self.turn) else: from_mask = self.pawns # Filter by source file. if match.group(2): from_mask &= BB_FILES[FILE_NAMES.index(match.group(2))] # Filter by source rank. if match.group(3): from_mask &= BB_RANKS[int(match.group(3)) - 1] # Match legal moves. matched_move = None for move in self.generate_legal_moves(from_mask, to_mask): if move.promotion != promotion: continue if matched_move: raise ValueError("ambiguous san: {!r} in {}".format(san, self.fen())) matched_move = move if not matched_move: raise ValueError("illegal san: {!r} in {}".format(san, self.fen())) return matched_move
[docs] def push_san(self, san: str) -> Move: """ Parses a move in standard algebraic notation, makes the move and puts it on the the move stack. Returns the move. :raises: :exc:`ValueError` if neither legal nor a null move. """ move = self.parse_san(san) self.push(move) return move
[docs] def uci(self, move: Move, *, chess960: Optional[bool] = None) -> str: """ Gets the UCI notation of the move. *chess960* defaults to the mode of the board. Pass ``True`` to force Chess960 mode. """ if chess960 is None: chess960 = self.chess960 move = self._to_chess960(move) move = self._from_chess960(chess960, move.from_square, move.to_square, move.promotion, move.drop) return move.uci()
[docs] def parse_uci(self, uci: str) -> Move: """ Parses the given move in UCI notation. Supports both Chess960 and standard UCI notation. The returned move is guaranteed to be either legal or a null move. :raises: :exc:`ValueError` if the move is invalid or illegal in the current position (but not a null move). """ move = Move.from_uci(uci) if not move: return move move = self._to_chess960(move) move = self._from_chess960(self.chess960, move.from_square, move.to_square, move.promotion, move.drop) if not self.is_legal(move): raise ValueError("illegal uci: {!r} in {}".format(uci, self.fen())) return move
[docs] def push_uci(self, uci: str) -> Move: """ Parses a move in UCI notation and puts it on the move stack. Returns the move. :raises: :exc:`ValueError` if the move is invalid or illegal in the current position (but not a null move). """ move = self.parse_uci(uci) self.push(move) return move
def xboard(self, move: Move, chess960: Optional[bool] = None) -> str: if chess960 is None: chess960 = self.chess960 if not chess960 or not self.is_castling(move): return move.xboard() elif self.is_kingside_castling(move): return "O-O" else: return "O-O-O" def parse_xboard(self, xboard: str) -> Move: if xboard == "@@@@": return Move.null() elif "," in xboard: raise ValueError("unsupported multi-leg xboard move: {!r}".format(xboard)) try: move = Move.from_uci(xboard) move = self._to_chess960(move) move = self._from_chess960(self.chess960, move.from_square, move.to_square, move.promotion, move.drop) if not self.is_legal(move): raise ValueError("illegal xboard move: {!r} in {}".format(xboard, self.fen())) return move except ValueError: pass try: return self.parse_san(xboard) except ValueError: raise ValueError("invalid or illegal xboard move: {!r} in {}".format(xboard, self.fen())) def push_xboard(self, xboard: str) -> Move: move = self.parse_xboard(xboard) self.push(move) return move
[docs] def is_en_passant(self, move: Move) -> bool: """Checks if the given pseudo-legal move is an en passant capture.""" return (self.ep_square == move.to_square and bool(self.pawns & BB_SQUARES[move.from_square]) and abs(move.to_square - move.from_square) in [7, 9] and not self.occupied & BB_SQUARES[move.to_square])
[docs] def is_capture(self, move: Move) -> bool: """Checks if the given pseudo-legal move is a capture.""" return bool(BB_SQUARES[move.to_square] & self.occupied_co[not self.turn]) or self.is_en_passant(move)
[docs] def is_zeroing(self, move: Move) -> bool: """Checks if the given pseudo-legal move is a capture or pawn move.""" return bool(BB_SQUARES[move.from_square] & self.pawns or BB_SQUARES[move.to_square] & self.occupied_co[not self.turn])
[docs] def is_irreversible(self, move: Move) -> bool: """ Checks if the given pseudo-legal move is irreversible. In standard chess, pawn moves, captures and moves that destroy castling rights are irreversible. """ backrank = BB_RANK_1 if self.turn == WHITE else BB_RANK_8 cr = self.clean_castling_rights() & backrank return bool(self.is_zeroing(move) or cr and BB_SQUARES[move.from_square] & self.kings & ~self.promoted or cr & BB_SQUARES[move.from_square] or cr & BB_SQUARES[move.to_square])
[docs] def is_castling(self, move: Move) -> bool: """Checks if the given pseudo-legal move is a castling move.""" if self.kings & BB_SQUARES[move.from_square]: diff = square_file(move.from_square) - square_file(move.to_square) return abs(diff) > 1 or bool(self.rooks & self.occupied_co[self.turn] & BB_SQUARES[move.to_square]) return False
[docs] def is_kingside_castling(self, move: Move) -> bool: """ Checks if the given pseudo-legal move is a kingside castling move. """ return self.is_castling(move) and square_file(move.to_square) > square_file(move.from_square)
[docs] def is_queenside_castling(self, move: Move) -> bool: """ Checks if the given pseudo-legal move is a queenside castling move. """ return self.is_castling(move) and square_file(move.to_square) < square_file(move.from_square)
[docs] def clean_castling_rights(self) -> Bitboard: """ Returns valid castling rights filtered from :data:`~chess.Board.castling_rights`. """ if self._stack: # Castling rights do not change in a game, so we can assume them to # be filtered already. return self.castling_rights castling = self.castling_rights & self.rooks white_castling = castling & BB_RANK_1 & self.occupied_co[WHITE] black_castling = castling & BB_RANK_8 & self.occupied_co[BLACK] if not self.chess960: # The rooks must be on a1, h1, a8 or h8. white_castling &= (BB_A1 | BB_H1) black_castling &= (BB_A8 | BB_H8) # The kings must be on e1 or e8. if not self.occupied_co[WHITE] & self.kings & ~self.promoted & BB_E1: white_castling = 0 if not self.occupied_co[BLACK] & self.kings & ~self.promoted & BB_E8: black_castling = 0 return white_castling | black_castling else: # The kings must be on the back rank. white_king_mask = self.occupied_co[WHITE] & self.kings & BB_RANK_1 & ~self.promoted black_king_mask = self.occupied_co[BLACK] & self.kings & BB_RANK_8 & ~self.promoted if not white_king_mask: white_castling = 0 if not black_king_mask: black_castling = 0 # There are only two ways of castling, a-side and h-side, and the # king must be between the rooks. white_a_side = white_castling & -white_castling white_h_side = BB_SQUARES[msb(white_castling)] if white_castling else 0 if white_a_side and msb(white_a_side) > msb(white_king_mask): white_a_side = 0 if white_h_side and msb(white_h_side) < msb(white_king_mask): white_h_side = 0 black_a_side = (black_castling & -black_castling) black_h_side = BB_SQUARES[msb(black_castling)] if black_castling else BB_EMPTY if black_a_side and msb(black_a_side) > msb(black_king_mask): black_a_side = 0 if black_h_side and msb(black_h_side) < msb(black_king_mask): black_h_side = 0 # Done. return black_a_side | black_h_side | white_a_side | white_h_side
[docs] def has_castling_rights(self, color: Color) -> bool: """Checks if the given side has castling rights.""" backrank = BB_RANK_1 if color == WHITE else BB_RANK_8 return bool(self.clean_castling_rights() & backrank)
[docs] def has_kingside_castling_rights(self, color: Color) -> bool: """ Checks if the given side has kingside (that is h-side in Chess960) castling rights. """ backrank = BB_RANK_1 if color == WHITE else BB_RANK_8 king_mask = self.kings & self.occupied_co[color] & backrank & ~self.promoted if not king_mask: return False castling_rights = self.clean_castling_rights() & backrank while castling_rights: rook = castling_rights & -castling_rights if rook > king_mask: return True castling_rights = castling_rights & (castling_rights - 1) return False
[docs] def has_queenside_castling_rights(self, color: Color) -> bool: """ Checks if the given side has queenside (that is a-side in Chess960) castling rights. """ backrank = BB_RANK_1 if color == WHITE else BB_RANK_8 king_mask = self.kings & self.occupied_co[color] & backrank & ~self.promoted if not king_mask: return False castling_rights = self.clean_castling_rights() & backrank while castling_rights: rook = castling_rights & -castling_rights if rook < king_mask: return True castling_rights = castling_rights & (castling_rights - 1) return False
[docs] def has_chess960_castling_rights(self) -> bool: """ Checks if there are castling rights that are only possible in Chess960. """ # Get valid Chess960 castling rights. chess960 = self.chess960 self.chess960 = True castling_rights = self.clean_castling_rights() self.chess960 = chess960 # Standard chess castling rights can only be on the standard # starting rook squares. if castling_rights & ~BB_CORNERS: return True # If there are any castling rights in standard chess, the king must be # on e1 or e8. if castling_rights & BB_RANK_1 and not self.occupied_co[WHITE] & self.kings & BB_E1: return True if castling_rights & BB_RANK_8 and not self.occupied_co[BLACK] & self.kings & BB_E8: return True return False
[docs] def status(self) -> Status: """ Gets a bitmask of possible problems with the position. Move making, generation and validation are only guaranteed to work on a completely valid board. :data:`~chess.STATUS_VALID` for a completely valid board. Otherwise, bitwise combinations of: :data:`~chess.STATUS_NO_WHITE_KING`, :data:`~chess.STATUS_NO_BLACK_KING`, :data:`~chess.STATUS_TOO_MANY_KINGS`, :data:`~chess.STATUS_TOO_MANY_WHITE_PAWNS`, :data:`~chess.STATUS_TOO_MANY_BLACK_PAWNS`, :data:`~chess.STATUS_PAWNS_ON_BACKRANK`, :data:`~chess.STATUS_TOO_MANY_WHITE_PIECES`, :data:`~chess.STATUS_TOO_MANY_BLACK_PIECES`, :data:`~chess.STATUS_BAD_CASTLING_RIGHTS`, :data:`~chess.STATUS_INVALID_EP_SQUARE`, :data:`~chess.STATUS_OPPOSITE_CHECK`, :data:`~chess.STATUS_EMPTY`, :data:`~chess.STATUS_RACE_CHECK`, :data:`~chess.STATUS_RACE_OVER`, :data:`~chess.STATUS_RACE_MATERIAL`. """ errors = STATUS_VALID # There must be at least one piece. if not self.occupied: errors |= STATUS_EMPTY # There must be exactly one king of each color. if not self.occupied_co[WHITE] & self.kings: errors |= STATUS_NO_WHITE_KING if not self.occupied_co[BLACK] & self.kings: errors |= STATUS_NO_BLACK_KING if popcount(self.occupied & self.kings) > 2: errors |= STATUS_TOO_MANY_KINGS # There can not be more than 16 pieces of any color. if popcount(self.occupied_co[WHITE]) > 16: errors |= STATUS_TOO_MANY_WHITE_PIECES if popcount(self.occupied_co[BLACK]) > 16: errors |= STATUS_TOO_MANY_BLACK_PIECES # There can not be more than 8 pawns of any color. if popcount(self.occupied_co[WHITE] & self.pawns) > 8: errors |= STATUS_TOO_MANY_WHITE_PAWNS if popcount(self.occupied_co[BLACK] & self.pawns) > 8: errors |= STATUS_TOO_MANY_BLACK_PAWNS # Pawns can not be on the back rank. if self.pawns & BB_BACKRANKS: errors |= STATUS_PAWNS_ON_BACKRANK # Castling rights. if self.castling_rights != self.clean_castling_rights(): errors |= STATUS_BAD_CASTLING_RIGHTS # En passant. if self.ep_square != self._valid_ep_square(): errors |= STATUS_INVALID_EP_SQUARE # Side to move giving check. if self.was_into_check(): errors |= STATUS_OPPOSITE_CHECK return errors
def _valid_ep_square(self) -> Optional[Square]: if not self.ep_square: return None if self.turn == WHITE: ep_rank = 5 pawn_mask = shift_down(BB_SQUARES[self.ep_square]) seventh_rank_mask = shift_up(BB_SQUARES[self.ep_square]) else: ep_rank = 2 pawn_mask = shift_up(BB_SQUARES[self.ep_square]) seventh_rank_mask = shift_down(BB_SQUARES[self.ep_square]) # The en passant square must be on the third or sixth rank. if square_rank(self.ep_square) != ep_rank: return None # The last move must have been a double pawn push, so there must # be a pawn of the correct color on the fourth or fifth rank. if not self.pawns & self.occupied_co[not self.turn] & pawn_mask: return None # And the en passant square must be empty. if self.occupied & BB_SQUARES[self.ep_square]: return None # And the second rank must be empty. if self.occupied & seventh_rank_mask: return None return self.ep_square
[docs] def is_valid(self) -> bool: """ Checks if the board is valid. Move making, generation and validation are only guaranteed to work on a completely valid board. See :func:`~chess.Board.status()` for details. """ return self.status() == STATUS_VALID
def _ep_skewered(self, king: Square, capturer: Square) -> bool: # Handle the special case where the king would be in check if the # pawn and its capturer disappear from the rank. # Vertical skewers of the captured pawn are not possible. (Pins on # the capturer are not handled here.) assert self.ep_square is not None last_double = self.ep_square + (-8 if self.turn == WHITE else 8) occupancy = (self.occupied & ~BB_SQUARES[last_double] & ~BB_SQUARES[capturer] | BB_SQUARES[self.ep_square]) # Horizontal attack on the fifth or fourth rank. horizontal_attackers = self.occupied_co[not self.turn] & (self.rooks | self.queens) if BB_RANK_ATTACKS[king][BB_RANK_MASKS[king] & occupancy] & horizontal_attackers: return True # Diagonal skewers. These are not actually possible in a real game, # because if the latest double pawn move covers a diagonal attack, # then the other side would have been in check already. diagonal_attackers = self.occupied_co[not self.turn] & (self.bishops | self.queens) if BB_DIAG_ATTACKS[king][BB_DIAG_MASKS[king] & occupancy] & diagonal_attackers: return True return False def _slider_blockers(self, king: Square) -> Bitboard: rooks_and_queens = self.rooks | self.queens bishops_and_queens = self.bishops | self.queens snipers = ((BB_RANK_ATTACKS[king][0] & rooks_and_queens) | (BB_FILE_ATTACKS[king][0] & rooks_and_queens) | (BB_DIAG_ATTACKS[king][0] & bishops_and_queens)) blockers = 0 for sniper in scan_reversed(snipers & self.occupied_co[not self.turn]): b = BB_BETWEEN[king][sniper] & self.occupied # Add to blockers if exactly one piece in-between. if b and BB_SQUARES[msb(b)] == b: blockers |= b return blockers & self.occupied_co[self.turn] def _is_safe(self, king: Square, blockers: Bitboard, move: Move) -> bool: if move.from_square == king: if self.is_castling(move): return True else: return not self.is_attacked_by(not self.turn, move.to_square) elif self.is_en_passant(move): return bool(self.pin_mask(self.turn, move.from_square) & BB_SQUARES[move.to_square] and not self._ep_skewered(king, move.from_square)) else: return bool(not blockers & BB_SQUARES[move.from_square] or BB_RAYS[move.from_square][move.to_square] & BB_SQUARES[king]) def _generate_evasions(self, king: Square, checkers: Bitboard, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: sliders = checkers & (self.bishops | self.rooks | self.queens) attacked = 0 for checker in scan_reversed(sliders): attacked |= BB_RAYS[king][checker] & ~BB_SQUARES[checker] if BB_SQUARES[king] & from_mask: for to_square in scan_reversed(BB_KING_ATTACKS[king] & ~self.occupied_co[self.turn] & ~attacked & to_mask): yield Move(king, to_square) checker = msb(checkers) if BB_SQUARES[checker] == checkers: # Capture or block a single checker. target = BB_BETWEEN[king][checker] | checkers yield from self.generate_pseudo_legal_moves(~self.kings & from_mask, target & to_mask) # Capture the checking pawn en passant (but avoid yielding # duplicate moves). if self.ep_square and not BB_SQUARES[self.ep_square] & target: last_double = self.ep_square + (-8 if self.turn == WHITE else 8) if last_double == checker: yield from self.generate_pseudo_legal_ep(from_mask, to_mask) def generate_legal_moves(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: if self.is_variant_end(): return king_mask = self.kings & self.occupied_co[self.turn] if king_mask: king = msb(king_mask) blockers = self._slider_blockers(king) checkers = self.attackers_mask(not self.turn, king) if checkers: for move in self._generate_evasions(king, checkers, from_mask, to_mask): if self._is_safe(king, blockers, move): yield move else: for move in self.generate_pseudo_legal_moves(from_mask, to_mask): if self._is_safe(king, blockers, move): yield move else: yield from self.generate_pseudo_legal_moves(from_mask, to_mask) def generate_legal_ep(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: if self.is_variant_end(): return for move in self.generate_pseudo_legal_ep(from_mask, to_mask): if not self.is_into_check(move): yield move def generate_legal_captures(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: return itertools.chain( self.generate_legal_moves(from_mask, to_mask & self.occupied_co[not self.turn]), self.generate_legal_ep(from_mask, to_mask)) def _attacked_for_king(self, path: Bitboard, occupied: Bitboard) -> bool: return any(self._attackers_mask(not self.turn, sq, occupied) for sq in scan_reversed(path)) def _castling_uncovers_rank_attack(self, rook_bb: Bitboard, king_to: Square) -> bool: # Test the special case where we castle and our rook shielded us from # an attack, so castling would be into check. rank_pieces = BB_RANK_MASKS[king_to] & (self.occupied ^ rook_bb) sliders = (self.queens | self.rooks) & self.occupied_co[not self.turn] return bool(BB_RANK_ATTACKS[king_to][rank_pieces] & sliders) def generate_castling_moves(self, from_mask: Bitboard = BB_ALL, to_mask: Bitboard = BB_ALL) -> Iterator[Move]: if self.is_variant_end(): return backrank = BB_RANK_1 if self.turn == WHITE else BB_RANK_8 king = self.occupied_co[self.turn] & self.kings & ~self.promoted & backrank & from_mask king = king & -king if not king or self._attacked_for_king(king, self.occupied): return bb_c = BB_FILE_C & backrank bb_d = BB_FILE_D & backrank bb_f = BB_FILE_F & backrank bb_g = BB_FILE_G & backrank for candidate in scan_reversed(self.clean_castling_rights() & backrank & to_mask): rook = BB_SQUARES[candidate] a_side = rook < king empty_for_rook = 0 empty_for_king = 0 if a_side: king_to = msb(bb_c) if not rook & bb_d: empty_for_rook = BB_BETWEEN[candidate][msb(bb_d)] | bb_d if not king & bb_c: empty_for_king = BB_BETWEEN[msb(king)][king_to] | bb_c else: king_to = msb(bb_g) if not rook & bb_f: empty_for_rook = BB_BETWEEN[candidate][msb(bb_f)] | bb_f if not king & bb_g: empty_for_king = BB_BETWEEN[msb(king)][king_to] | bb_g if not ((self.occupied ^ king ^ rook) & (empty_for_king | empty_for_rook) or self._attacked_for_king(empty_for_king, self.occupied ^ king) or self._castling_uncovers_rank_attack(rook, king_to)): yield self._from_chess960(self.chess960, msb(king), candidate) def _from_chess960(self, chess960: bool, from_square: Square, to_square: Square, promotion: Optional[PieceType] = None, drop: Optional[PieceType] = None) -> Move: if not chess960 and promotion is None and drop is None: if from_square == E1 and self.kings & BB_E1: if to_square == H1: return Move(E1, G1) elif to_square == A1: return Move(E1, C1) elif from_square == E8 and self.kings & BB_E8: if to_square == H8: return Move(E8, G8) elif to_square == A8: return Move(E8, C8) return Move(from_square, to_square, promotion, drop) def _to_chess960(self, move: Move) -> Move: if move.from_square == E1 and self.kings & BB_E1: if move.to_square == G1 and not self.rooks & BB_G1: return Move(E1, H1) elif move.to_square == C1 and not self.rooks & BB_C1: return Move(E1, A1) elif move.from_square == E8 and self.kings & BB_E8: if move.to_square == G8 and not self.rooks & BB_G8: return Move(E8, H8) elif move.to_square == C8 and not self.rooks & BB_C8: return Move(E8, A8) return move def _transposition_key(self) -> Hashable: return (self.pawns, self.knights, self.bishops, self.rooks, self.queens, self.kings, self.occupied_co[WHITE], self.occupied_co[BLACK], self.turn, self.clean_castling_rights(), self.ep_square if self.has_legal_en_passant() else None) def __repr__(self) -> str: if not self.chess960: return "{}({!r})".format(type(self).__name__, self.fen()) else: return "{}({!r}, chess960=True)".format(type(self).__name__, self.fen()) def _repr_svg_(self) -> str: import chess.svg return chess.svg.board( board=self, size=400, lastmove=self.peek() if self.move_stack else None, check=self.king(self.turn) if self.is_check() else None) def __eq__(self, board: object) -> bool: if isinstance(board, Board): return ( self.halfmove_clock == board.halfmove_clock and self.fullmove_number == board.fullmove_number and type(self).uci_variant == type(board).uci_variant and self._transposition_key() == board._transposition_key()) else: return NotImplemented def apply_transform(self, f: Callable[[Bitboard], Bitboard]) -> None: super().apply_transform(f) self.clear_stack() def transform(self: BoardT, f: Callable[[Bitboard], Bitboard]) -> BoardT: board = self.copy(stack=False) board.apply_transform(f) board.ep_square = None if self.ep_square is None else msb(f(BB_SQUARES[self.ep_square])) board.castling_rights = f(self.castling_rights) return board
[docs] def mirror(self: BoardT) -> BoardT: board = super().mirror() board.turn = not self.turn return board
[docs] def copy(self: BoardT, *, stack: Union[bool, int] = True) -> BoardT: """ Creates a copy of the board. Defaults to copying the entire move stack. Alternatively, *stack* can be ``False``, or an integer to copy a limited number of moves. """ board = super().copy() board.chess960 = self.chess960 board.ep_square = self.ep_square board.castling_rights = self.castling_rights board.turn = self.turn board.fullmove_number = self.fullmove_number board.halfmove_clock = self.halfmove_clock if stack: stack = len(self.move_stack) if stack is True else stack board.move_stack = [copy.copy(move) for move in self.move_stack[-stack:]] board._stack = self._stack[-stack:] return board
[docs] @classmethod def empty(cls: Type[BoardT], *, chess960: bool = False) -> BoardT: """Creates a new empty board. Also see :func:`~chess.Board.clear()`.""" return cls(None, chess960=chess960)
[docs] @classmethod def from_epd(cls: Type[BoardT], epd: str, *, chess960: bool = False) -> Tuple[BoardT, Dict[str, Union[None, str, int, float, Move, List[Move]]]]: """ Creates a new board from an EPD string. See :func:`~chess.Board.set_epd()`. Returns the board and the dictionary of parsed operations as a tuple. """ board = cls.empty(chess960=chess960) return board, board.set_epd(epd)
[docs] @classmethod def from_chess960_pos(cls: Type[BoardT], sharnagl: int) -> BoardT: board = cls.empty(chess960=True) board.set_chess960_pos(sharnagl) return board
class PseudoLegalMoveGenerator: def __init__(self, board: Board) -> None: self.board = board def __bool__(self) -> bool: return any(self.board.generate_pseudo_legal_moves()) def count(self) -> int: # List conversion is faster than iterating. return len(list(self)) def __iter__(self) -> Iterator[Move]: return self.board.generate_pseudo_legal_moves() def __contains__(self, move: Move) -> bool: return self.board.is_pseudo_legal(move) def __repr__(self) -> str: builder = [] for move in self: if self.board.is_legal(move): builder.append(self.board.san(move)) else: builder.append(self.board.uci(move)) sans = ", ".join(builder) return "<PseudoLegalMoveGenerator at {:#x} ({})>".format(id(self), sans) class LegalMoveGenerator: def __init__(self, board: Board) -> None: self.board = board def __bool__(self) -> bool: return any(self.board.generate_legal_moves()) def count(self) -> int: # List conversion is faster than iterating. return len(list(self)) def __iter__(self) -> Iterator[Move]: return self.board.generate_legal_moves() def __contains__(self, move: Move) -> bool: return self.board.is_legal(move) def __repr__(self) -> str: sans = ", ".join(self.board.san(move) for move in self) return "<LegalMoveGenerator at {:#x} ({})>".format(id(self), sans) IntoSquareSet = Union[SupportsInt, Iterable[Square]]
[docs]class SquareSet: """ A set of squares. >>> import chess >>> >>> squares = chess.SquareSet([chess.A8, chess.A1]) >>> squares SquareSet(0x0100000000000001) >>> squares = chess.SquareSet(chess.BB_A8 | chess.BB_RANK_1) >>> squares SquareSet(0x01000000000000ff) >>> print(squares) 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 1 1 1 1 1 1 >>> len(squares) 9 >>> bool(squares) True >>> chess.B1 in squares True >>> for square in squares: ... # 0 -- chess.A1 ... # 1 -- chess.B1 ... # 2 -- chess.C1 ... # 3 -- chess.D1 ... # 4 -- chess.E1 ... # 5 -- chess.F1 ... # 6 -- chess.G1 ... # 7 -- chess.H1 ... # 56 -- chess.A8 ... print(square) ... 0 1 2 3 4 5 6 7 56 >>> list(squares) [0, 1, 2, 3, 4, 5, 6, 7, 56] Square sets are internally represented by 64-bit integer masks of the included squares. Bitwise operations can be used to compute unions, intersections and shifts. >>> int(squares) 72057594037928191 Also supports common set operations like :func:`~chess.SquareSet.issubset()`, :func:`~chess.SquareSet.issuperset()`, :func:`~chess.SquareSet.union()`, :func:`~chess.SquareSet.intersection()`, :func:`~chess.SquareSet.difference()`, :func:`~chess.SquareSet.symmetric_difference()` and :func:`~chess.SquareSet.copy()` as well as :func:`~chess.SquareSet.update()`, :func:`~chess.SquareSet.intersection_update()`, :func:`~chess.SquareSet.difference_update()`, :func:`~chess.SquareSet.symmetric_difference_update()` and :func:`~chess.SquareSet.clear()`. """ def __init__(self, squares: IntoSquareSet = BB_EMPTY) -> None: try: self.mask = squares.__int__() & BB_ALL # type: ignore return except AttributeError: self.mask = 0 # Try squares as an iterable. Not under except clause for nicer # backtraces. for square in squares: # type: ignore self.add(square) # Set def __contains__(self, square: Square) -> bool: return bool(BB_SQUARES[square] & self.mask) def __iter__(self) -> Iterator[Square]: return scan_forward(self.mask) def __reversed__(self) -> Iterator[Square]: return scan_reversed(self.mask) def __len__(self) -> int: return popcount(self.mask) # MutableSet
[docs] def add(self, square: Square) -> None: """Adds a square to the set.""" self.mask |= BB_SQUARES[square]
[docs] def discard(self, square: Square) -> None: """Discards a square from the set.""" self.mask &= ~BB_SQUARES[square]
# frozenset
[docs] def isdisjoint(self, other: IntoSquareSet) -> bool: """Test if the square sets are disjoint.""" return not bool(self & other)
[docs] def issubset(self, other: IntoSquareSet) -> bool: """Test if this square set is a subset of another.""" return not bool(~self & other)
[docs] def issuperset(self, other: IntoSquareSet) -> bool: """Test if this square set is a superset of another.""" return not bool(self & ~SquareSet(other))
def union(self, other: IntoSquareSet) -> "SquareSet": return self | other def __or__(self, other: IntoSquareSet) -> "SquareSet": r = SquareSet(other) r.mask |= self.mask return r def intersection(self, other: IntoSquareSet) -> "SquareSet": return self & other def __and__(self, other: IntoSquareSet) -> "SquareSet": r = SquareSet(other) r.mask &= self.mask return r def difference(self, other: IntoSquareSet) -> "SquareSet": return self - other def __sub__(self, other: IntoSquareSet) -> "SquareSet": r = SquareSet(other) r.mask = self.mask & ~r.mask return r def symmetric_difference(self, other: IntoSquareSet) -> "SquareSet": return self ^ other def __xor__(self, other: IntoSquareSet) -> "SquareSet": r = SquareSet(other) r.mask ^= self.mask return r def copy(self) -> "SquareSet": return SquareSet(self.mask) # set def update(self, *others: IntoSquareSet) -> None: for other in others: self |= other def __ior__(self, other: IntoSquareSet) -> "SquareSet": self.mask |= SquareSet(other).mask return self def intersection_update(self, *others: IntoSquareSet) -> None: for other in others: self &= other def __iand__(self, other: IntoSquareSet) -> "SquareSet": self.mask &= SquareSet(other).mask return self def difference_update(self, other: IntoSquareSet) -> None: self -= other def __isub__(self, other: IntoSquareSet) -> "SquareSet": self.mask &= ~SquareSet(other).mask return self def symmetric_difference_update(self, other: IntoSquareSet) -> None: self ^= other def __ixor__(self, other: IntoSquareSet) -> "SquareSet": self.mask ^= SquareSet(other).mask return self
[docs] def remove(self, square: Square) -> None: """ Removes a square from the set. :raises: :exc:`KeyError` if the given square was not in the set. """ mask = BB_SQUARES[square] if self.mask & mask: self.mask ^= mask else: raise KeyError(square)
[docs] def pop(self) -> Square: """ Removes a square from the set and returns it. :raises: :exc:`KeyError` on an empty set. """ if not self.mask: raise KeyError("pop from empty SquareSet") square = lsb(self.mask) self.mask &= (self.mask - 1) return square
[docs] def clear(self) -> None: """Remove all elements from this set.""" self.mask = BB_EMPTY
# SquareSet
[docs] def carry_rippler(self) -> Iterator[Bitboard]: """Iterator over the subsets of this set.""" return _carry_rippler(self.mask)
[docs] def mirror(self) -> "SquareSet": """Returns a vertically mirrored copy of this square set.""" return SquareSet(flip_vertical(self.mask))
[docs] def tolist(self) -> List[bool]: """Convert the set to a list of 64 bools.""" result = [False] * 64 for square in self: result[square] = True return result
def __bool__(self) -> bool: return bool(self.mask) def __eq__(self, other: object) -> bool: try: return self.mask == SquareSet(other).mask # type: ignore except (TypeError, ValueError): return NotImplemented def __lshift__(self, shift: int) -> "SquareSet": return SquareSet((self.mask << shift) & BB_ALL) def __rshift__(self, shift: int) -> "SquareSet": return SquareSet(self.mask >> shift) def __ilshift__(self, shift: int) -> "SquareSet": self.mask = (self.mask << shift) & BB_ALL return self def __irshift__(self, shift: int) -> "SquareSet": self.mask >>= shift return self def __invert__(self) -> "SquareSet": return SquareSet(~self.mask & BB_ALL) def __int__(self) -> int: return self.mask def __index__(self) -> int: return self.mask def __repr__(self) -> str: return "SquareSet({0:#018x})".format(self.mask) def __str__(self) -> str: builder = [] for square in SQUARES_180: mask = BB_SQUARES[square] builder.append("1" if self.mask & mask else ".") if not mask & BB_FILE_H: builder.append(" ") elif square != H1: builder.append("\n") return "".join(builder) def _repr_svg_(self) -> str: import chess.svg return chess.svg.board(squares=self, size=400)
[docs] @classmethod def from_square(cls, square: Square) -> "SquareSet": """ Creates a :class:`~chess.SquareSet` from a single square. >>> import chess >>> >>> chess.SquareSet.from_square(chess.A1) == chess.BB_A1 True """ return cls(BB_SQUARES[square])