dynamic bases

[Niels Diepeveen]

Balazs Scheidler schreef:
> My other attempt was to use __getattr__ hooks to return attributes in a way
> that attributes of A are returned in case __dict__ of B doesn't contain a
> given name. Functions were bound to the instance of B, then the Python
> interpreter complained that self is not a subclass of B.

If you want to do it as cleanly as possible, you can use something like
this:

class DynaMethod:
    def __init__(self, instance, function):
        self.instance = instance
        self.function = function
    def __call__(self, *args, **kwargs):
        apply(self.function, (self.instance,) + args, kwargs)

if __name__ == '__main__':
    # test code
    def method_a(self):
        print 'Doing a now on object %s' % id(self)
        
    def method_b(self, arg1):
        print 'Doing b with argument %s' % repr(arg1)
        
    class A:
        def __init__(self):
            self.method_a = DynaMethod(self, method_a)
            self.method_b = DynaMethod(self, method_b)
    a = A()
    print 'Created instance %s' % id(a)
    dir(a)
    a.method_a()
    a.method_b('test')

This does take some extra memory and time though. A more efficient, but
probably implementation-dependent way would be to use
new.instancemethod().

-- 
Niels Diepeveen
Endea automatisering