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Groups > comp.lang.python > #32715

Re: is implemented with id ?

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On Sun, Nov 4, 2012 at 2:10 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> /* Shortcut for empty or interned objects */
> if (v == u) {
>     Py_DECREF(u);
>     Py_DECREF(v);
>     return 0;
> }
> result = unicode_compare(u, v);
>
> where v and u are pointers to the unicode object.

There's a shortcut if they're the same. There's no shortcut if they're
both interned and have different pointers, which is a guarantee that
they're distinct strings. They'll still be compared char-for-char
until there's a difference.

But it probably isn't enough of a performance penalty to be concerned
with. It's enough to technically prove the point that 'is' is faster
than '==' and is still safe if both strings are interned; it's not
enough to make 'is' better than '==', except in very specific
situations.

ChrisA

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is implemented with id ? Franck Ditter <franck@ditter.org> - 2012-09-05 08:30 +0200
  Re: is implemented with id ? Benjamin Kaplan <benjamin.kaplan@case.edu> - 2012-09-04 23:40 -0700
    Re: is implemented with id ? Franck Ditter <franck@ditter.org> - 2012-09-05 15:19 +0200
      Re: is implemented with id ? Hans Mulder <hansmu@xs4all.nl> - 2012-09-05 15:48 +0200
        Re: is implemented with id ? aahz@pythoncraft.com (Aahz) - 2012-11-03 12:41 -0700
          Re: is implemented with id ? Hans Mulder <hansmu@xs4all.nl> - 2012-11-03 22:49 +0100
            Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-03 22:18 +0000
              Re: is implemented with id ? Chris Angelico <rosuav@gmail.com> - 2012-11-04 09:50 +1100
              Re: is implemented with id ? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2012-11-04 01:14 +0000
                Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-04 03:10 +0000
                Re: is implemented with id ? Chris Angelico <rosuav@gmail.com> - 2012-11-04 14:19 +1100
                Re: is implemented with id ? aahz@pythoncraft.com (Aahz) - 2012-11-03 22:09 -0700
                Re: is implemented with id ? Hans Mulder <hansmu@xs4all.nl> - 2012-11-04 11:13 +0100
              Re: is implemented with id ? Chris Angelico <rosuav@gmail.com> - 2012-11-04 12:22 +1100
              Re: is implemented with id ? aahz@pythoncraft.com (Aahz) - 2012-11-03 22:08 -0700
            Re: is implemented with id ? Roy Smith <roy@panix.com> - 2012-11-03 18:41 -0400
            Re: is implemented with id ? aahz@pythoncraft.com (Aahz) - 2012-11-03 22:12 -0700
      Re: is implemented with id ? Dave Angel <d@davea.name> - 2012-09-05 10:00 -0400
        Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-05 14:41 +0000
          Re: is implemented with id ? Dave Angel <d@davea.name> - 2012-09-05 11:09 -0400
            Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-05 15:36 +0000
            Re: is implemented with id ? Hans Mulder <hansmu@xs4all.nl> - 2012-09-05 18:47 +0200
              Re: is implemented with id ? Dave Angel <d@davea.name> - 2012-09-05 13:19 -0400
          Re: is implemented with id ? Terry Reedy <tjreedy@udel.edu> - 2012-09-05 14:31 -0400
          Re: is implemented with id ? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-09-05 22:08 -0400
          Re: is implemented with id ? Duncan Booth <duncan.booth@invalid.invalid> - 2012-09-06 09:34 +0000
            Re: is implemented with id ? Chris Angelico <rosuav@gmail.com> - 2012-09-06 19:50 +1000
          Re: is implemented with id ? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-11-04 01:33 -0700
  Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-05 09:14 +0000
    Re: is implemented with id ? Ramchandra Apte <maniandram01@gmail.com> - 2012-09-05 05:48 -0700
      Re: is implemented with id ? Dave Angel <d@davea.name> - 2012-09-05 09:46 -0400
      Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-05 14:13 +0000
        Re: is implemented with id ? Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-05 11:08 -0600
        Re: is implemented with id ? Chris Angelico <rosuav@gmail.com> - 2012-09-06 19:07 +1000
      Re: is implemented with id ? Terry Reedy <tjreedy@udel.edu> - 2012-09-05 14:27 -0400
        Re: is implemented with id ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-06 06:44 +0000
          Re: is implemented with id ? Ramchandra Apte <maniandram01@gmail.com> - 2012-09-06 01:24 -0700
          Re: is implemented with id ? Roy Smith <roy@panix.com> - 2012-09-06 08:16 -0400
            Re: is implemented with id ? Ramchandra Apte <maniandram01@gmail.com> - 2012-09-06 06:30 -0700
      Re: is implemented with id ? Dave Angel <d@davea.name> - 2012-09-05 14:40 -0400

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