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Groups > comp.lang.python > #84514

Re: Delegation in Python

References <FeCdnXdsTpunvlnJnZ2dnUVZ8judnZ2d@brightview.co.uk>
Date 2015-01-25 10:22 +1100
Subject Re: Delegation in Python
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.18106.1422141738.18130.python-list@python.org> (permalink)

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On Sun, Jan 25, 2015 at 9:57 AM, Brian Gladman <noone@nowhere.net> wrote:
> But I am not clear on how to delegate from my new class to the existing
> Fraction class.  This is what I have:
>
> --------------------------
> class RF(Fraction):
>
>   def __new__(self, x, y):
>     super().__new__(self, x, y)
>
>   def is_integer(self):
>     return self.numerator % self.denominator == 0
>
>   def __getattr__(self, attr):
>     return getattr(self, attr)

If you just drop everything but your new method, it should work just fine.

class RF(Fraction):
    def is_integer(self):
       return self.numerator % self.denominator == 0

However, this doesn't ensure that operations on RFs will return more
RFs - they'll often return Fractions instead. There's no easy fix for
that, sorry.

ChrisA

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Thread

Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-24 22:57 +0000
  Re: Delegation in Python Chris Angelico <rosuav@gmail.com> - 2015-01-25 10:22 +1100
    Re: Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-24 23:38 +0000
      Re: Delegation in Python Chris Angelico <rosuav@gmail.com> - 2015-01-25 10:43 +1100
        Re: Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-25 00:18 +0000
          Re: Delegation in Python Chris Angelico <rosuav@gmail.com> - 2015-01-25 11:28 +1100
            Re: Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-25 07:49 +0000
              Re: Delegation in Python Chris Angelico <rosuav@gmail.com> - 2015-01-25 19:07 +1100
      Re: Delegation in Python Gary Herron <gherron@digipen.edu> - 2015-01-24 15:47 -0800
        Re: Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-24 23:58 +0000
  Re: Delegation in Python Gary Herron <gherron@digipen.edu> - 2015-01-24 15:41 -0800
    Re: Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-24 23:52 +0000
  Re: Delegation in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-24 23:59 +0000
  Re: Delegation in Python Chris Angelico <rosuav@gmail.com> - 2015-01-25 11:07 +1100
  Re: Delegation in Python Terry Reedy <tjreedy@udel.edu> - 2015-01-24 20:31 -0500
    Re: Delegation in Python Brian Gladman <noone@nowhere.net> - 2015-01-25 07:43 +0000

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