Re: [Python-Dev] Dinamically set call method

From	Gregory Ewing <greg.ewing@canterbury.ac.nz>
Newsgroups	comp.lang.python
Subject	Re: [Python-Dev] Dinamically set __call__ method
Date	2014-11-13 17:20 +1300
Message-ID	<ccips8Fs5j8U1@mid.individual.net> (permalink)
References	(7 earlier) <8761eq424e.fsf@handshake.de> <mailman.15584.1415476169.18130.python-list@python.org> <cc7jtiFubltU1@mid.individual.net> <CALwzidnE9ZeHV6nM74hKX58LhZ0ova5qB60-eWbw2gLTtk+O3Q@mail.gmail.com> <mailman.15726.1415806493.18130.python-list@python.org>

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Fabio Zadrozny wrote:
> can someone from python-dev give some background of why 
> that's the way it is?

It's because, with new-style classes, a class is also an
instance (of class "type" or a subclass thereof). So
without that rule, it would be ambiguous whether a dunder
method applied to instances of a class or to the class
itself.

 > 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

Something fairly fundamental that would break is classs
instantiation! You instantiate a class by calling it, so if
a(x) were implemented as a.__call__(x), and class C had
a __call__ method, then C() would invoke that method
instead of instantiating C.

-- 
Greg

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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