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Re: while True or while 1

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在 2012年1月24日星期二UTC+8上午4时50分11秒，Andrea Crotti写道：
> On 01/23/2012 06:05 PM, Evan Driscoll wrote:
> >
> > To play devil's advocate for a moment, if you have the choice between 
> > two ways of writing something, A and B, where both are basically the 
> > same in terms of difficulty to write, difficulty to maintain, and 
> > difficulty to understand, but A is faster than B, even if just by a 
> > hair, why NOT write A?
> >
> > It's like 'iter++' vs '++iter' in a C++ for loop. For ints, or for 
> > some iterators with optimization, it makes no difference. But the 
> > latter will be faster in debug builds, and *might* be faster in 
> > release builds if you have a complicated iterator. So why NOT make 
> > for(...; ...; ++i) the typical way of writing a for loop?
> >
> > In the Python world, is 'while 1' any harder to understand than 'while 
> > True'? I'm about as staunch a supporter as you'll find for the idea 
> > that 'while 1' should throw an exception, and even *I* think that 
> > 'while 1' is about the least-offensive idiom out there. If 'while 1' 
> > throws you off, I'd hate to see what you do when you learn that Python 
> > accepts loops like 'while x' where the condition evaluates to true if 
> > x is a non-zero integer and false if x is 0.
> >
> >
> > All that said, I like the 'while "stuff to do"' idea.
> >
> > Evan
> 
> I think it's not the same, iter++ or ++iter is exactly the same in terms 
> of readability, so of course
> if one might be a bit faster, it should be used.
> 
> while 1 works because the 1 is converted to boolean automatically, but 
> why not just writing a boolean
> in the first place?
> 
> It's not bad of course but to me it's not very Pythonic, and reminds me C.
> At that point I also prefer the "while 'might be long loop'" idea, which 
> at least
> adds some value *and* it might be very slightly faster too.

 A fake generator that can't be cascaded for more processing  can be called
 an iterator by the definition of an iterator. 

But that is miss-leading in implementing silly trivial non-qualified iterators.

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Re: while True or while 1 Chris Angelico <rosuav@gmail.com> - 2012-01-22 01:59 +1100
  Re: while True or while 1 Erik Max Francis <max@alcyone.com> - 2012-01-21 13:13 -0800
    Re: while True or while 1 Chris Angelico <rosuav@gmail.com> - 2012-01-22 09:13 +1100
      Re: while True or while 1 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-01-22 05:25 +0000
        Re: while True or while 1 Dan Sommers <dan@tombstonezero.net> - 2012-01-22 16:05 +0000
          Re: while True or while 1 alex23 <wuwei23@gmail.com> - 2012-01-22 19:55 -0800
            Re: while True or while 1 Dave Angel <d@davea.name> - 2012-01-23 08:02 -0500
              Re: while True or while 1 Hrvoje Niksic <hniksic@xemacs.org> - 2012-01-23 14:28 +0100
                Re: while True or while 1 Dave Angel <d@davea.name> - 2012-01-23 13:33 -0500
        Re: while True or while 1 MRAB <python@mrabarnett.plus.com> - 2012-01-22 16:13 +0000
    Re: while True or while 1 Grant Edwards <invalid@invalid.invalid> - 2012-01-23 15:51 +0000
    Re: while True or while 1 Giampaolo Rodolà <g.rodola@gmail.com> - 2012-01-23 17:41 +0100
      Re: while True or while 1 Erik Max Francis <max@alcyone.com> - 2012-01-23 11:12 -0800
        Re: while True or while 1 Giampaolo Rodolà <g.rodola@gmail.com> - 2012-01-23 21:20 +0100
    Re: while True or while 1 Ian Kelly <ian.g.kelly@gmail.com> - 2012-01-23 10:39 -0700
    Re: while True or while 1 Evan Driscoll <edriscoll@wisc.edu> - 2012-01-23 12:05 -0600
    Re: while True or while 1 Andrea Crotti <andrea.crotti.0@gmail.com> - 2012-01-23 20:50 +0000
      Re: while True or while 1 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-23 14:42 -0800
      Re: while True or while 1 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-23 14:42 -0800
      Re: while True or while 1 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-01-24 03:37 +0000

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