def from_fen(cls, fen_str):
# Separate the 6 components
board_str, active_colour_str, castling_str, en_passant_str,\
half_move_str, full_move_str = fen_str.strip().split(' ')
position = Position()
# Construct the board
board = tuple()
for rank_str in board_str.split('/'):
rank = tuple()
for piece_str in rank_str:
if piece_str in '12345678':
# Blanks
rank += (None,) * int(piece_str)
else:
# Piece
piece_colour = WHITE if piece_str.isupper() else BLACK
rank += (cls.mappings[piece_str.upper()](piece_colour),)
board = (rank,) + board
# Rest of Properties
position.board = board
position.active_colour = WHITE if active_colour_str=='w' else BLACK
position.castling = '' if castling_str is '-' else castling_str
position.en_passant = None if en_passant_str=='-' else get_coord_from_rank_file(en_passant_str)
position.half_move = int(half_move_str)
position.full_move = int(full_move_str)
return position
def new_game(board_str = None):
"""Creates a new game based on text representation"""
mappings = {'R': Rook, 'N': Knight, 'B': Bishop, 'Q': Queen, 'K': King, 'P': Pawn}
position = Position()
if board_str is None:
# White plays North
board_str = (' rnbqkbnr\n' #8
' pppppppp\n' #7
' ........\n' #6
' ........\n' #5
' ........\n' #4
' ........\n' #3
' PPPPPPPP\n' #2
' RNBQKBNR') #1
# abcdefgh
# Permute the board so that Top left become bottom left
board_str = board_str.replace(' ', '').replace('\n','')
ranks = reversed([board_str[i:i+8] for i in range(0, 64, 8)])
board_str = ''.join(ranks)
board = ()
rank = ()
for piece in board_str:
if piece == '.':
rank += (None,)
elif piece.isupper():
rank += (mappings[piece.upper()](WHITE), )
elif piece.islower():
rank += (mappings[piece.upper()](BLACK), )
if len(rank) == 8:
board += (rank,)
rank = ()
position.board=board
return position
