1.txt

def aStarAlgo(start_node,stop_node):
 open_set=set(start_node)
 closed_set=set()
 g={}
 parents={}
 g[start_node]=0
 parents[start_node]=start_node
 while len(open_set)> 0:
 n=None
 for v in open_set:
 if n == None or g[v]+ heuristic(v) < g[n]+heuristic(n):
 n=v
 if n==stop_node or Graph_nodes[n]==None:
 pass
 else:
 for(m,weight)in get_neighbors(n):
 if m not in open_set and m not in closed_set:
 open_set.add(m)
 parents[m]=n
 g[m]=g[n]+weight
 else:
 if g[m]>g[n]+weight:
 g[m]=g[n]+weight
 parents[m]=n
 if m in closed_set:
 closed_set.remove(m)
 open_set.add(m)
 if n==None:
 print('Path does not exist!')
 return None
 if n==stop_node:
 path=[]
 while parents[n]!=n:
 path.append(n)
 n=parents[n]
 path.append(start_node)
 path.reverse()
 print('Path found:{}'.format(path))
 return path
 open_set.remove(n)
 closed_set.add(n)
 print('Path does not exist!')
 return None
def get_neighbors(v):
 if v in Graph_nodes:
 return Graph_nodes[v]
 else:
 return None
def heuristic(n):
 H_dist={
 'A':11,
 'B':6,
 'C':99,
 'D':1,
 'E':7,
 'G':0,
 }
 return H_dist[n]
Graph_nodes={
 'A':[('B',2),('E',3)],
 'B':[('C',1),('G',9)],
 'C':None,
 'E':[('D',6)],
 'D':[('G',1)],
 }
aStarAlgo('A','G')