python实现类之间的方法互相调用

from son import *
class ALL():
 def __init__(self):
  self.mSon = SON(self)
 def getAll(self):
  print "=================getall---------------"
  return self.mSon.getSon()
 def getAlltest(self):
  print "=================getAlltest---------------"
Instance = ALL()
Instance.getAll()

class SON():
 def __init__(self, instance):
 self.mBattle = instance
 def getSon(self):
 return self.mBattle.getAlltest()