[Tutor] overriding instance attributes with keywords

[Gregory, Matthew]

Hi all,

I'm trying to create a new instance from an existing instance with attributes of the new instance allowed to be overwritten by keyword parameters.  I'm guessing I'm not doing this in the most efficient manner.

class Spam:
    def __init__(self, a, b):
        self.a = a
        self.b = b
    def __repr__(self):
        return "%s: (%d,%d)" % (self.__class__.__name__, self.a, self.b)

def new_with_overrides(s1, **kwargs):
    new_params = {'a': s1.a, 'b': s1.b}
    for (k, v) in kwargs.iteritems():
        if k in new_params:
            new_params[k] = v
    return Spam(new_params['a'], new_params['b'])

s1 = Spam(4, 10)
s2 = new_with_overrides(s1)
s3 = new_with_overrides(s1, a=3)
s4 = new_with_overrides(s1, b=7)

This works but it doesn't seem very extendable if new attributes are added to Spam.  I know that I can make new_with_overrides a method of Spam and that may simplify things a bit (e.g. using __dict__).

thanks, matt