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Groups > comp.lang.python > #32289

Re: while expression feature proposal

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On 10/26/12 19:18, Steven D'Aprano wrote:
> def iterate_until_none_or_false(func, *args, **kwargs):
>     while True:
>         x = func(*args, **kwargs)
>         # Halt if x is None or False, but not other falsey values.
>         if x is None or x is False:
>             return
>         yield x
> 
> for x in iterate_until_none_or_false(
>         some_function, 1, 2, "c", spam="yummy"):
>     process(x)

I was initially a pretty strong advocate of the proposed "as"
syntax.  However, the more I've thought about it, the more I keep
coming back to how I've solved the problem in the past which is
mostly what Steven suggests here.  There are so many edge-cases and
warts in the "as" syntax; most of which disappear with this
generator+forloop:

- yielding/unpacking multiple results  each time: the "as" syntax
would get really ugly.  Do you test the whole result, or an element
of the result?

- knowing the stopping condition varies: is it when something is
False-ish (an empty string/tuple/list, False, None, etc)?  When it
"is None"?  When it is exactly "False"?

- the whole "x = (foo(bar) as result) if result else None" (or
should that be "x = result if (foo(bar) as result) else None"?)
style/discussion just really looks ugly to me.  Usually I find
Python code quite beautiful and this syntax doesn't resonate as
"beautiful".

To despite my previous excitement, I'm now neutral at best on a
limited "while TERM as VAR:" syntax.

I know this "being persuaded by rational arguments and changing
one's mind" thing is rare on the Intarwebs, so I hope I haven't
upset the natural balance of things too greatly. :-)

-tkc

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Re: while expression feature proposal Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-24 16:54 -0600
  Re: while expression feature proposal Paul Rubin <no.email@nospam.invalid> - 2012-10-24 16:08 -0700
    Re: while expression feature proposal Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-24 17:39 -0600
      Re: while expression feature proposal Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-10-25 09:21 +0200
        Re: while expression feature proposal Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-10-25 12:12 +0200
        Re: while expression feature proposal Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-25 10:36 -0600
          Re: while expression feature proposal Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-10-25 22:49 +0200
            Re: while expression feature proposal Dan Loewenherz <dloewenherz@gmail.com> - 2012-10-25 22:12 -0700
              Re: while expression feature proposal Paul Rubin <no.email@nospam.invalid> - 2012-10-25 23:06 -0700
                Re: while expression feature proposal Chris Angelico <rosuav@gmail.com> - 2012-10-26 17:23 +1100
                Re: while expression feature proposal Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-26 09:43 +0000
                Re: while expression feature proposal Dan Loewenherz <dloewenherz@gmail.com> - 2012-10-26 08:29 -0700
                Re: while expression feature proposal Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-26 09:42 -0600
                Re: while expression feature proposal Paul Rubin <no.email@nospam.invalid> - 2012-10-26 09:10 -0700
                Re: while expression feature proposal Cameron Simpson <cs@zip.com.au> - 2012-10-27 09:03 +1100
                Re: while expression feature proposal Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-26 16:48 -0600
                Re: while expression feature proposal Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-27 00:07 +0000
                Re: while expression feature proposal Paul Rubin <no.email@nospam.invalid> - 2012-10-26 20:43 -0700
                Re: while expression feature proposal Tim Chase <sed@thechases.com> - 2012-10-26 18:26 -0500
                Re: while expression feature proposal Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-10-26 19:41 -0400
                Re: while expression feature proposal Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-10-26 19:19 -0400
                Re: while expression feature proposal Chris Angelico <rosuav@gmail.com> - 2012-10-27 11:42 +1100
              Re: while expression feature proposal Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-10-26 19:12 -0400
                Re: while expression feature proposal Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-27 00:18 +0000
                Re: while expression feature proposal Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-10-26 20:27 -0400
                Re: while expression feature proposal Tim Chase <python.list@tim.thechases.com> - 2012-10-27 14:15 -0500
              Re: while expression feature proposal Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-10-26 19:51 -0400
        Re: while expression feature proposal Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-25 10:47 -0600
    Re: while expression feature proposal Paul Rudin <paul.nospam@rudin.co.uk> - 2012-10-25 10:35 +0100

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