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Re: while expression feature proposal

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Am 25.10.2012 01:39 schrieb Ian Kelly:
> On Wed, Oct 24, 2012 at 5:08 PM, Paul Rubin <no.email@nospam.invalid> wrote:
>> from itertools import dropwhile
>>
>> j = dropwhile(lambda j: j in selected,
>>                   iter(lambda: int(random() * n), object()))
>>               .next()
>>
>> kind of ugly, makes me wish for a few more itertools primitives, but I
>> think it expresses reasonably directly what you are trying to do.
>
> Nice, although a bit opaque.  I think I prefer it as a generator expression:
>
> j = next(j for j in iter(partial(randrange, n), None) if j not in selected)

This generator never ends. If it meets a non-matching value, it just 
skips it and goes on.

The dropwhile expression, however, stops as soon as the value is found.

I think

# iterate ad inf., because partial never returns None:
i1 = iter(partial(randrange, n), None)
# take the next value, make it None for breaking:
i2 = (j if j in selected else None for j in i1)
# and now, break on None:
i3 = iter(lambda: next(i2), None)

would do the job.


Thomas

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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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