i have 
class Foo(object):

   def __init__(self, a=1, b=2):

      self.a=a
      self.b=b

and a lot of 
class Bla(Foo):

   def __init__(self, a=1, b=2, t=3, h=8):

      self.t=t
      self.h=h
      Foo.__init__(self, a=a, b=b)


now i wants to "extend" Foo in my module and add c=3 in __init__ i.e.

class Foo(Foo):

   def __init__(self, a=1, b=2, c=3):

      self.c=c
      Foo.__init__(self, a=a, b=b)

the goal is:
t=Bla(a=11, b=22, c=33)

whithout Bla modification... if this possible? how do you usually do such things?