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astar.py
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astar.py
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# Author: Christian Careaga (christian.careaga7@gmail.com)
# A* Pathfinding in Python (2.7)
# Please give credit if used
import numpy
from heapq import *
def heuristic(a, b):
return abs(b[0] - a[0]) + abs(b[1] - a[1])
def astar(array, start, goal):
neighbors = [(0,1),(0,-1),(1,0),(-1,0)]
close_set = set()
came_from = {}
gscore = {start:0}
fscore = {start:heuristic(start, goal)}
oheap = []
heappush(oheap, (fscore[start], start))
while oheap:
current = heappop(oheap)[1]
if current == goal:
data = []
while current in came_from:
data.append(current)
current = came_from[current]
return data
close_set.add(current)
for i, j in neighbors:
neighbor = current[0] + i, current[1] + j
tentative_g_score = gscore[current] + heuristic(current, neighbor)
if 0 <= neighbor[0] < array.shape[0]:
if 0 <= neighbor[1] < array.shape[1]:
if array[neighbor[0]][neighbor[1]] == 1:
continue
else:
# array bound y walls
continue
else:
# array bound x walls
continue
if neighbor in close_set and tentative_g_score >= gscore.get(neighbor, 0):
continue
if tentative_g_score < gscore.get(neighbor, 0) or neighbor not in [i[1]for i in oheap]:
came_from[neighbor] = current
gscore[neighbor] = tentative_g_score
fscore[neighbor] = tentative_g_score + heuristic(neighbor, goal)
heappush(oheap, (fscore[neighbor], neighbor))
return False
'''Here is an example of using my algo with a numpy array,
astar(array, start, destination)
astar function returns a list of points (shortest path)'''
nmap = numpy.array([
[0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[1,1,1,1,1,1,1,1,1,1,1,1,0,1],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[1,0,1,1,1,1,1,1,1,1,1,1,1,1],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[1,1,1,1,1,1,1,1,1,1,1,1,0,1],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[1,0,1,1,1,1,1,1,1,1,1,1,1,1],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0],
[1,1,1,1,1,1,1,1,1,1,1,1,0,1],
[0,0,0,0,0,0,0,0,0,0,0,0,0,0]])
print (astar(nmap, (0,0), (1,0)))