Re: [Python-Dev] Dinamically set call method

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From	Fabio Zadrozny <fabiofz@gmail.com>
Date	Wed, 12 Nov 2014 13:33:57 -0200
Subject	Re: [Python-Dev] Dinamically set __call__ method
To	Ian Kelly <ian.g.kelly@gmail.com>
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On Tue, Nov 11, 2014 at 5:43 AM, Ian Kelly <ian.g.kelly@gmail.com> wrote:

> On Sat, Nov 8, 2014 at 3:31 PM, Gregory Ewing
> <greg.ewing@canterbury.ac.nz> wrote:
> > (BTW, I'm actually surprised that this technique makes c callable.
> > There must be more going on that just "look up __call__ in the class
> > object", because evaluating C.__call__ just returns the descriptor
> > and doesn't invoking the descriptor mechanism.)
>
> But of course it doesn't just lookup C.__call__, because it has to
> bind the method to the instance before calling it, which means
> invoking the descriptor protocol. The actual lookup is more like:
>
> type(a).__dict__['__call__'].__get__(a, type(a))
> --
> https://mail.python.org/mailman/listinfo/python-list
>

As a reference, I recently found a blog post related to that:
http://lucumr.pocoo.org/2014/8/16/the-python-i-would-like-to-see/ (the
Slots part comments on that).

It does seem a bit counter-intuitive that this happens the way it does
though, so, can someone from python-dev give some background of why that's
the way it is? i.e.: instead of the approach which would seem simpler which
would do getattr(a, '__call__') instead of
type(a).__dict__['__call__'].__get__(a, type(a)) -- it seems to me it's
mostly because of historical reasons, but I'm really curious why is it so
(and if maybe it's something which python-dev would consider worth changing
in the future -- not sure how much could break because of that though).

Thanks and Best Regards,

Fabio

Thread

Re: [Python-Dev] Dinamically set __call__ method Ethan Furman <ethan@stoneleaf.us> - 2014-11-04 11:12 -0800
  Re: [Python-Dev] Dinamically set __call__ method John Ladasky <john_ladasky@sbcglobal.net> - 2014-11-06 12:21 -0800
    Re: [Python-Dev] Dinamically set __call__ method dieter <dieter@handshake.de> - 2014-11-07 07:59 +0100
    Re: [Python-Dev] Dinamically set __call__ method Ethan Furman <ethan@stoneleaf.us> - 2014-11-07 04:58 -0800
    Re: [Python-Dev] Dinamically set __call__ method dieter <dieter@handshake.de> - 2014-11-08 07:50 +0100
    Re: [Python-Dev] Dinamically set __call__ method Ethan Furman <ethan@stoneleaf.us> - 2014-11-08 11:49 -0800
      Re: [Python-Dev] Dinamically set __call__ method Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-09 11:31 +1300
        Re: [Python-Dev] Dinamically set __call__ method Ethan Furman <ethan@stoneleaf.us> - 2014-11-08 19:27 -0800
          Re: [Python-Dev] Dinamically set __call__ method Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-10 00:38 +1300
            Re: [Python-Dev] Dinamically set __call__ method Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-10 00:14 +1100
            Re: [Python-Dev] Dinamically set __call__ method Ethan Furman <ethan@stoneleaf.us> - 2014-11-09 12:16 -0800
        Re: [Python-Dev] Dinamically set __call__ method Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-11 00:43 -0700
        Re: [Python-Dev] Dinamically set __call__ method Fabio Zadrozny <fabiofz@gmail.com> - 2014-11-12 13:33 -0200
          Re: [Python-Dev] Dinamically set __call__ method Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-11-13 17:20 +1300
            Re: [Python-Dev] Dinamically set __call__ method Fabio Zadrozny <fabiofz@gmail.com> - 2014-11-13 11:38 -0200
        Re: [Python-Dev] Dinamically set __call__ method Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-12 11:58 -0700

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