class test1(list):
    val=0
    def __iter__(self):
        if self.val == 0:
            print 'first pass in test1.__iter__'
            self.val=1
            self.__iter__=self.__str__
            return list.__iter__(self)
        else:
            print 'still passing in test1.__iter__'
            return list.__iter__(self)
    
b=test1((1,2))

for i in b:
    pass
print b.__iter__
for i in b:
    pass