On 25/01/2015 00:28, Chris Angelico wrote: > On Sun, Jan 25, 2015 at 11:18 AM, Brian Gladman <no...@nowhere.net> wrote: >> Is there a way of doing delegation rather than sub-classing? >> >> That is, can I create a class (say RF) that passes some of its methods >> to Fraction for implementation but always returns an RF? > > Hmm. The key here is that you want more than just delegation; you want > to transform every return value. That's not going to be easy. It would > be easiest and cleanest to skip the whole thing, and have a separate > function for what you're doing here - not a method, a stand-alone > function. > > def is_integer(fr): > return fr.numerator % fr.denominator == 0 > > Next best would be the monkey-patching option. Delegation with > transformation is a lot of effort for what you want.
Thanks, a part of this was a wish to understand how to map what I can do in other languages into Python. I felt that it might just be possible in Python to avoid having to wrap all the methods of the base class in the derived class. But it seems that __getattr__ etc are not quite as magic as I hoped. Thanks again for your help. Brian -- https://mail.python.org/mailman/listinfo/python-list
