Python does not support function overload since it's a dynamic language, see:
Overloaded functions in python?
If I understand you correctly, you need super
to call the method of your base class from your child class:
In [95]: class Base(object):
...: def __init__(self, x):
...: print 'in Base.ctor, x is:', x
...:
...: class Child(Base):
...: def __init__(self, x, y):
...: super(Child, self).__init__(x)
In [96]: c = Child(1,2)
in Base.ctor, x is: 1
see: Understanding Python super() with __init__() methods