using attributes as defaults

[Wanderer]

I want to give the option of changing attributes in a method or using
the current values of the attributes as the default.

class MyClass():
     """  my Class
     """
     def __init__(self):
          """ initialize
          """
          self.a = 3
          self.b = 4

     def MyMethod(self, a = self.a, b = self.b)
          """ My Method
          """
          self.a = a
          self.b = b
          DoSomething(a, b)

The above doesn't work. Is there a way to make it work?

Thanks