Every object in Python has a __dict__ member, which stores the object's attributes.
So, you can do something like this:
class surf(object):
def __init__(self, arg1, arg2, **kwargs):
#do stuff with arg1 and arg2
self.__dict__.update(kwargs)
s = surf('arg1', 'arg2', bar=20, baz=10)
# Here s is a object of surf with two extra attributes.