Re: [Python-Dev] Dinamically set call method

Path	csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!us.feeder.erje.net!newsfeed.fsmpi.rwth-aachen.de!news-1.dfn.de!news.dfn.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From	Gregory Ewing <greg.ewing@canterbury.ac.nz>
Newsgroups	comp.lang.python
Subject	Re: [Python-Dev] Dinamically set __call__ method
Date	Thu, 13 Nov 2014 17:20:22 +1300
Lines	22
Message-ID	<ccips8Fs5j8U1@mid.individual.net> (permalink)
References	<CAF0TK51TKs+tw=u_rzrWVeSsDK7cOBt1Gcvq_izLfMObuDYNig@mail.gmail.com> <545919B6.7040007@stoneleaf.us> <CAF0TK52vw_SmqexN8RXyGs8GSKecPobK54ZqYPyKgRSSJy9zWw@mail.gmail.com> <mailman.15467.1415128339.18130.python-list@python.org> <c25aa612-bff2-4982-8fb9-5b17a866bead@googlegroups.com> <87a943qyvn.fsf@handshake.de> <545CC204.2010301@stoneleaf.us> <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>
Mime-Version	1.0
Content-Type	text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding	7bit
X-Trace	individual.net 9IYOiOga7zIYtk4m4IPh8QXfzeZzWSDVffB7fi7yFICTvOBVIx
Cancel-Lock	sha1:iewVcUYfz5jAkjNXbY778FuWJmw=
User-Agent	Mozilla Thunderbird 1.0.5 (Macintosh/20050711)
X-Accept-Language	en-us, en
In-Reply-To	<mailman.15726.1415806493.18130.python-list@python.org>
Xref	csiph.com comp.lang.python:80667

Show key headers only | View raw

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

csiph-web