python-chess: a pure Python chess library

Introduction

This is the scholars mate in python-chess:

board = chess.Bitboard()
board.push_san("e4")
board.push_san("e5")
board.push_san("Qh5")
board.push_san("Nc6")
board.push_san("Bc4")
board.push_san("Nf6")
board.push_san("Qxf7")
assert board.is_checkmate()

Documentation

http://pythonhosted.org/python-chess/core.html

Features

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

  assert not chess.Move.from_uci("a8a1") in board.legal_moves
  

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

  assert not board.is_stalemate()
  assert not board.is_insufficient_material()
  assert board.is_game_over()
  

• Detects checks and attacks.

  assert board.is_check()
  assert board.is_attacked_by(chess.WHITE, chess.E8)
  

• Parses and creates SAN representation of moves.

  board = chess.Bitboard()
  assert "e4" == board.san(chess.Move(chess.E2, chess.E4))
  

• Parses and creates FENs.

  assert board.fen() == "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
  board = chess.Bitboard("8/8/8/2k5/4K3/8/8/8 w - - 4 45")
  assert board.piece_at(chess.C5) == chess.Piece.from_symbol("k")
  

• Parses and creates EPDs.

  assert board.epd(bm=chess.Move.from_uci("d2d4")) == "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - bm d4"
  
  ops = board.set_epd("1k1r4/pp1b1R2/3q2pp/4p3/2B5/4Q3/PPP2B2/2K5 b - - bm Qd1+; id \"BK.01\";")
  assert ops["id"] == "BK.01"
  assert ops["bm"] == chess.Move(chess.D6, chess.D1)
  

• Read Polyglot opening books.

  import chess.polyglot
  
  with chess.polyglot.open_reader("data/opening-books/performance.bin") as book:
      board = chess.Bitboard()
  
      for entry in book.get_entries_for_position(board):
           assert chess.Move.from_uci("e2e4") == entry.move()
           break
  

Peformance

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

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

Installing

• With pip:

  sudo pip install python-chess
  

• From current source code:

  python setup.py build
  sudo python setup.py install
  

License

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

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