you're setting the new knight's "sl" to the value self.sl and then adding values to it. that's the same list - so you are adding values to the self.sl list when you add them to the knight's sl.
this is easier to understand just by seeing the fix, which is to use: temp = Knight(self.x, self.y, self.g, self.h, self.gp, list(self.sl)) which will make a new copy of the list, so you are only adding to the sl in the (new) knight. andrew dlocpuwons wrote: > Using Python 2.6.1... > > I am (attempting) to make an A* search for a chess problem, but I am > running into a really annoying shared memory issue in my successor > function. Here it is stripped down to the important parts that relate > to my problem. > > def successors(self): > result = [] > moves = [[2, 1], [2, -1], [-2, 1], [-2, -1], [1, 2], [1, -2], > [-1, > 2], [-1, -2]] #possible moves for a knight > > for i in moves: > temp = Knight(self.x, self.y, self.g, self.h, self.gp, > self.sl) > temp.x += i[0] > temp.y += i[1] > temp.sl.append([temp.x, temp.y]) #Adds the new current > state to the > visited states list > result.append(temp) > return result > > The method creates a temporary Knight object, increments it to the new > position and then adds this new position to its list of visited > states. Then it returns a list of these 8 new objects. The problem > seems to be with the "result.sl.append()" line. As the method chugs > along and creates the new objects the "temp.sl" lines seems to stay in > memory, so when the method is done all the new objects have all the > new states that were made over the course of the method instead of > just their own created in the loop. For example when I try to get > successors for a piece that is initially at (2,2) with no previously > visited states, the method prints this out for the sl (state list) > value > > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > [[2, 2], [4, 3], [4, 1], [0, 3], [0, 1], [3, 4], [3, 0], [1, 4], [1, > 0]] > > but what it should print out is > > [[2, 2], [4, 3]] > [[2, 2], [4, 1]] > [[2, 2], [0, 3]] > [[2, 2], [0, 1]] > [[2, 2], [3, 4]] > [[2, 2], [3, 0]] > [[2, 2], [1, 4]] > [[2, 2], [1, 0]] > > It sort of seems like python is trying to be too smart and is trying > to keep things in memory. Is there anyway to work around this? > -- > http://mail.python.org/mailman/listinfo/python-list > > -- http://mail.python.org/mailman/listinfo/python-list
