SGF Parser & Board State for Go / Baduk

sgf.py

import sys

class Board(object):
    def __init__(self, size):
        self.size = size
        self.grid = {}
    def move(self, color, x, y):
        self.set(color, x, y)
        for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
            nx = x + dx
            ny = y + dy
            cell = self.get(nx, ny) 
            if cell and cell != color:
                group, liberties = self.group(nx, ny)
                if liberties == 0:
                    self.remove_group(group)
    def get(self, x, y):
        return self.grid.get((x, y))
    def set(self, color, x, y):
        self.grid[(x, y)] = color
    def remove_group(self, group):
        for x, y in group:
            self.grid.pop((x, y))
    def group(self, x, y):
        color = self.get(x, y)
        if not color:
            return []
        result = set()
        perimeter = {}
        self._group(x, y, color, result, perimeter)
        liberties = perimeter.values().count(None)
        return sorted(result), liberties
    def _group(self, x, y, color, result, perimeter):
        if x < 0 or y < 0 or x >= self.size or y >= self.size:
            return
        if (x, y) in result:
            return
        cell = self.get(x, y)
        if cell != color:
            perimeter[(x, y)] = cell
            return
        result.add((x, y))
        self._group(x - 1, y, color, result, perimeter)
        self._group(x + 1, y, color, result, perimeter)
        self._group(x, y - 1, color, result, perimeter)
        self._group(x, y + 1, color, result, perimeter)
    def __str__(self):
        rows = []
        for y in range(self.size):
            row = []
            for x in range(self.size):
                row.append(self.get(x, y) or '.')
            rows.append(' '.join(row))
        return '\n'.join(rows)

def parse(filename):
    result = []
    with open(filename) as fp:
        for line in fp:
            line = line.strip()
            if line.startswith(';B') or line.startswith(';W'):
                color = line[1]
                x = ord(line[3]) - ord('a')
                y = ord(line[4]) - ord('a')
                result.append((color, x, y))
    return result

def main():
    moves = parse(sys.argv[1])
    board = Board(19)
    for i, (color, x, y) in enumerate(moves):
        board.move(color, x, y)
    black = [k for k, v in board.grid.items() if v == 'B']
    white = [k for k, v in board.grid.items() if v == 'W']
    print board
    print black
    print white

if __name__ == '__main__':
    main()