DFS

stack = []def DFS():        def findpath():                global pos                global dest                global stack                # This eats O(intersections) stack                val = valid(neighbours0(pos[0],pos[1]))                try:                        val.remove(stack[-1])                except IndexError:                        # Should possibly only happen on the first entry                        pass                if val:                        stack.append(pos)                        for path in val:                                pos = path                                search(path)                                if pos == dest or findpath(): return True                        pos = stack.pop()                return False        findpath()