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 class AStar(object): def __init__(self, graph): self.graph = graph def heuristic(self, node, start, end): raise NotImplementedError def search(self, start, end): openset = set() closedset = set() current = start openset.add(current) while openset: current = min(openset, key=lambda o:o.g + o.h) if current == end: path = [] while current.parent: path.append(current) current = current.parent path.append(current) return path[::-1] openset.remove(current) closedset.add(current) for node in self.graph[current]: if node in closedset: continue if node in openset: new_g = current.g + current.move_cost(node) if node.g > new_g: node.g = new_g node.parent = current else: node.g = current.g + current.move_cost(node) node.h = self.heuristic(node, start, end) node.parent = current openset.add(node) return None class AStarNode(object): def __init__(self): self.g = 0 self.h = 0 self.parent = None def move_cost(self, other): raise NotImplementedError
 from astar import AStar, AStarNode from math import sqrt class AStarGrid(AStar): def heuristic(self, node, start, end): # NOTE: this is traditionally sqrt((end.x - node.x)**2 + (end.y - node.y)**2) # However, if you are not interested in the *actual* cost, but only relative cost, # then the math can be simplified. return abs(end.x - node.x) + abs(end.y - node.y) #return sqrt((end.x - node.x)**2 + (end.y - node.y)**2) class AStarGridNode(AStarNode): def __init__(self, x, y): self.x, self.y = x, y super(AStarGridNode, self).__init__() def move_cost(self, other): diagonal = abs(self.x - other.x) == 1 and abs(self.y - other.y) == 1 return 14 if diagonal else 10 def __repr__(self): return '(%d %d)' % (self.x, self.y)
 #! /usr/bin/env python from astar_grid import AStarGrid, AStarGridNode from itertools import product def make_graph(mapinfo): nodes = [[AStarGridNode(x, y) for y in range(mapinfo['height'])] for x in range(mapinfo['width'])] graph = {} for x, y in product(range(mapinfo['width']), range(mapinfo['height'])): node = nodes[x][y] graph[node] = [] for i, j in product([-1, 0, 1], [-1, 0, 1]): if not (0 <= x + i < mapinfo['width']): continue if not (0 <= y + j < mapinfo['height']): continue if [x+i,y+j] in mapinfo['obstacle']: continue graph[nodes[x][y]].append(nodes[x+i][y+j]) return graph, nodes graph, nodes = make_graph({"width": 8, "height": 8, "obstacle": [[2,5],[3,5],[4,5],[5,5]]}) paths = AStarGrid(graph) start, end = nodes[1][1], nodes[5][7] path = paths.search(start, end) if path is None: print "No path found" else: print "Path found:", path
 Copyright (C) 2012 Justin Poliey Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

### KasunRama commented May 31, 2014

 Can you please tell me how to replace the start and end with user defined coordinates. I gave "start, end = (x1, y1), (x2, y2)" but it returns "no path found"

### giantsnark commented Jun 23, 2014

 @KasunRama: Because you're calling an AStarGrid object when doing the search, the inputs must be AStarGridNode objects as defined in astar_grid.py. The example grid of AStarGridNode objects you're looking for is created on line 7 of example_grid.py. Your custom start and end points should be written as: start, end = nodes[x1][y1], nodes[x2][y2]

### PeterJacob commented Oct 23, 2014

 I don't fully agree with your comment about changing the heuristic. You changed the Euclidean distance to the Manhattan distance. If you are truely interested in the Euclidean distance, but only care about the rank (relative distance) the formula should be (end.x - node.x)**2 + (end.y - node.y)**2.