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Groups > comp.lang.python > #34281
| From | Neil Cerutti <neilc@norwich.edu> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: Good use for itertools.dropwhile and itertools.takewhile |
| Date | 2012-12-05 14:34 +0000 |
| Organization | Norwich University |
| Message-ID | <ai94btF9hoaU1@mid.individual.net> (permalink) |
| References | <b80f3ab3-ef81-4806-86db-efd5800d4bb3@googlegroups.com> <mailman.474.1354653865.29569.python-list@python.org> <05bca175-2077-4fb8-917e-baee1a43a47d@googlegroups.com> <mailman.490.1354715109.29569.python-list@python.org> |
On 2012-12-05, Chris Angelico <rosuav@gmail.com> wrote:
> On Wed, Dec 5, 2012 at 12:17 PM, Nick Mellor <thebalancepro@gmail.com> wrote:
>>
>> takewhile mines for gold at the start of a sequence, dropwhile
>> drops the dross at the start of a sequence.
>
> When you're using both over the same sequence and with the same
> condition, it seems odd that you need to iterate over it twice.
> Perhaps a partitioning iterator would be cleaner - something
> like this:
>
> def partitionwhile(predicate, iterable):
> iterable = iter(iterable)
> while True:
> val = next(iterable)
> if not predicate(val): break
> yield val
> raise StopIteration # Signal the end of Phase 1
> for val in iterable: yield val # or just "yield from iterable", I think
>
> Only the cold hard boot of reality just stomped out the spark
> of an idea. Once StopIteration has been raised, that's it,
> there's no "resuming" the iterator. Is there a way around that?
> Is there a clean way to say "Done for now, but next time you
> ask, there'll be more"?
>
> I tested it on Python 3.2 (yeah, time I upgraded, I know).
Well, shoot! Then this is a job for groupby, not takewhile.
def prod_desc(s):
"""split s into product name and product description.
>>> prod_desc("CAR FIFTY TWO Chrysler LeBaron.")
['CAR FIFTY TWO', 'Chrysler LeBaron.']
>>> prod_desc("MR. JONESEY Saskatchewan's finest")
['MR. JONESEY', "Saskatchewan's finest"]
>>> prod_desc("no product name?")
['', 'no product name?']
>>> prod_desc("NO DESCRIPTION")
['NO DESCRIPTION', '']
"""
prod = ''
desc = ''
for k, g in itertools.groupby(s.split(),
key=lambda w: any(c.islower() for c in w)):
a = ' '.join(g)
if k:
desc = a
else:
prod = a
return [prod, desc]
This has no way to preserve odd white space which could break
evil product name differences.
--
Neil Cerutti
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Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-04 05:57 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-04 14:23 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-04 06:47 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-04 15:17 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Vlastimil Brom <vlastimil.brom@gmail.com> - 2012-12-04 15:31 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-04 07:24 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Vlastimil Brom <vlastimil.brom@gmail.com> - 2012-12-04 22:08 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-04 07:24 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-04 18:26 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Alexander Blinne <news@blinne.net> - 2012-12-04 18:18 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile DJC <djc@news.invalid> - 2012-12-04 18:28 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Alexander Blinne <news@blinne.net> - 2012-12-04 19:48 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Ian Kelly <ian.g.kelly@gmail.com> - 2012-12-04 12:37 -0700
Re: Good use for itertools.dropwhile and itertools.takewhile Alexander Blinne <news@blinne.net> - 2012-12-04 21:33 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-12-04 21:13 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile MRAB <python@mrabarnett.plus.com> - 2012-12-04 20:17 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Terry Reedy <tjreedy@udel.edu> - 2012-12-04 15:44 -0500
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-04 17:17 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Chris Angelico <rosuav@gmail.com> - 2012-12-06 00:45 +1100
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-05 14:34 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Ian Kelly <ian.g.kelly@gmail.com> - 2012-12-05 08:33 -0700
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-05 16:11 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-12-05 15:32 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Ian Kelly <ian.g.kelly@gmail.com> - 2012-12-05 09:16 -0700
Re: Good use for itertools.dropwhile and itertools.takewhile MRAB <python@mrabarnett.plus.com> - 2012-12-05 17:57 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-04 17:17 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-05 13:29 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-05 09:04 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile MRAB <python@mrabarnett.plus.com> - 2012-12-05 17:57 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-05 18:16 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Nick Mellor <thebalancepro@gmail.com> - 2012-12-05 11:01 -0800
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-05 20:13 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Vlastimil Brom <vlastimil.brom@gmail.com> - 2012-12-05 22:36 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Neil Cerutti <neilc@norwich.edu> - 2012-12-06 13:06 +0000
Re: Good use for itertools.dropwhile and itertools.takewhile Vlastimil Brom <vlastimil.brom@gmail.com> - 2012-12-06 15:12 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Alexander Blinne <news@blinne.net> - 2012-12-06 14:40 +0100
Re: Good use for itertools.dropwhile and itertools.takewhile Terry Reedy <tjreedy@udel.edu> - 2012-12-04 17:21 -0500
Re: Good use for itertools.dropwhile and itertools.takewhile Paul Rubin <no.email@nospam.invalid> - 2012-12-06 13:29 -0800
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