How to do this?

[flyaflya]

the codes as  follow:
class Base:
    def fun(self):
        print "base_fun"
    def fun2(self):
        print "base_fun2"

class Foo:
 def  __init__(self, base):
  self.__base = base
 def fun3(self):
  print  "foo_fun3"

b = Base()
foo = Foo(b)

my aim is:when "foo.fun3()" be called,it run as usually, but when
"foo.fun()" or "foo.fun2() be called, as Foo hasn't attribute "fun()" and
"fun2()", foo will call "self.__base.fun()" or "self.__base.fun2()".
when a attr can't be find in foo, it's will try to search 'self.__base". I
think this maybe need to use  "__getattr__" and "__setattr__" ,but I cant do
it successfully. can someone  help  me?