#<ex.py>

  class B(object):
      def __init__(self, *args):
          print "B.__init__"
          super(B, self).__init__(*args)

  class M(B, type):
      def __init__(self, n, b, d):
          print "M.__init__"
          super(M, self).__init__(n, b, d)
       
  class C(B):
      __metaclass__ = M
      def __init__(self):
          print "C.__init__"
          super(C, self).__init__()

 #</ex.py>

>>> from ex import C
M.__init__
B.__init__
>>> c = C()
C.__init__
B.__init__