python go

board.py

    def place_stone(self, player, point):
        assert self.is_on_grid(point)
        assert self._grid.get(point) is None
        adjacent_same_color = []
        adjacent_opposite_color = []
        liberties = []
        
# First, we examine direct neighbors of this point.
        for neighbor in point.neighbors():  
            if not self.is_on_grid(neighbor):
                continue
            neighbor_string = self._grid.get(neighbor)
            if neighbor_string is None:
                liberties.append(neighbor)
            elif neighbor_string.color == player:
                if neighbor_string not in adjacent_same_color:
                    adjacent_same_color.append(neighbor_string)
            else:
                if neighbor_string not in adjacent_opposite_color:
                    adjacent_opposite_color.append(neighbor_string)
                    
        new_string = GoString(player, [point], liberties)

# Merge any adjacent strings of the same color.
        for same_color_string in adjacent_same_color:  
            new_string = new_string.merged_with(same_color_string)
        for new_string_point in new_string.stones:
            self._grid[new_string_point] = new_string
# Reduce liberties of any adjacent strings of the opposite color.
        for other_color_string in adjacent_opposite_color:  
            other_color_string.remove_liberty(point)
# If any opposite color strings now have zero liberties, remove them.
        for other_color_string in adjacent_opposite_color:  
            if other_color_string.num_liberties == 0:
                self._remove_string(other_color_string)