Re: why does dead code costs time?

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Date	Wed, 5 Dec 2012 19:24:13 +0100
From	Bruno Dupuis <python.ml.bruno.dupuis@lisael.org>
To	python-list@python.org
Subject	Re: why does dead code costs time?
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On Wed, Dec 05, 2012 at 10:59:26AM -0700, Ian Kelly wrote:
> On Wed, Dec 5, 2012 at 10:34 AM, Steven D'Aprano
> <steve+comp.lang.python@pearwood.info> wrote:
> > The difference is almost certain between the LOAD_CONST and the
> > LOAD_GLOBAL.
> >
> > As to *why* there is such a difference, I believe that's a leftover from
> > early Python days when None was not a keyword and could be reassigned.
> 
> I think this should even be considered a bug, not just a missing
> optimization.  Consider:

This is definitely a bug

> >>> globals()['None'] = 42
> >>> def f(x):
> ...     return None
> ...     print(x)
> ...
> >>> f('test')
> 42

This one is pretty scary

The difference between `return None` and `return` leads to inconsistency and
is in contradiction with the specs, AFAIK. I'm glad we pointed this out.

-- 
Bruno Dupuis

Thread

why does dead code costs time? Bruno Dupuis <python.ml.bruno.dupuis@lisael.org> - 2012-12-05 16:46 +0100
  Re: why does dead code costs time? Neil Cerutti <neilc@norwich.edu> - 2012-12-05 16:15 +0000
    Re: why does dead code costs time? Bruno Dupuis <python.ml.bruno.dupuis@lisael.org> - 2012-12-05 17:40 +0100
      Re: why does dead code costs time? Ramchandra Apte <maniandram01@gmail.com> - 2012-12-09 06:11 -0800
        Re: why does dead code costs time? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-12-09 16:47 +0000
          Re: why does dead code costs time? Ramchandra Apte <maniandram01@gmail.com> - 2012-12-12 21:23 -0800
            Re: why does dead code costs time? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-12-13 06:01 +0000
              Re: why does dead code costs time? rusi <rustompmody@gmail.com> - 2012-12-12 22:27 -0800
                Re: why does dead code costs time? Cameron Simpson <cs@zip.com.au> - 2012-12-13 17:51 +1100
                Re: why does dead code costs time? rusi <rustompmody@gmail.com> - 2012-12-12 22:59 -0800
                Re: why does dead code costs time? Chris Angelico <rosuav@gmail.com> - 2012-12-13 18:03 +1100
          Re: why does dead code costs time? Ramchandra Apte <maniandram01@gmail.com> - 2012-12-12 21:23 -0800
    Re: why does dead code costs time? Bruno Dupuis <python.ml.bruno.dupuis@lisael.org> - 2012-12-05 18:19 +0100
      Re: why does dead code costs time? Tim Roberts <timr@probo.com> - 2012-12-05 21:20 -0800
  Re: why does dead code costs time? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-12-05 17:34 +0000
    Re: why does dead code costs time? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-12-05 17:39 +0000
    Re: why does dead code costs time? Ian Kelly <ian.g.kelly@gmail.com> - 2012-12-05 10:59 -0700
    Re: why does dead code costs time? Bruno Dupuis <python.ml.bruno.dupuis@lisael.org> - 2012-12-05 19:24 +0100
    Re: why does dead code costs time? Terry Reedy <tjreedy@udel.edu> - 2012-12-05 15:41 -0500
    Re: why does dead code costs time? Chris Kaynor <ckaynor@zindagigames.com> - 2012-12-05 12:49 -0800
    Re: why does dead code costs time? Bruno Dupuis <python.ml.bruno.dupuis@lisael.org> - 2012-12-05 21:50 +0100
    Re: why does dead code costs time? Bruno Dupuis <python.ml.bruno.dupuis@lisael.org> - 2012-12-05 22:58 +0100

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