class Graph():
 def __init__(self, V, E):
 self.V = V
 self.E = E
 self.visited = []
 self.dict = {}
 self.fd = open("input.txt")
 def initGraph(self):
 self.visited = [0 for i in range(self.V+1)]
 for i in range(self.E):
 f, t = map(int, self.fd.readline().split())
 #f, t = map(int, sys.stdin.readline().split())
 if self.dict.has_key(f)==False:
 l = []
 l.append(t)
 self.dict[f] = l
 else:
 l = self.dict[f]
 l.append(t)
 self.dict[f] = l
 
 def dfsGraph(self, src):
 self.visited[src] = 1
 print src ,
 if self.dict.get(src): #self.dict[src]会出现异常
 for u in self.dict[src]:
 if self.visited[u]==0:
 self.dfsGraph(u)
graph = Graph(6, 10)
graph.initGraph()
graph.dfsGraph(1)
nput.txt
 代码如下:
output: 
 代码如下: