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Modification to "pairwise" in itertools recipes #49600
Description
| BPO | 5350 |
|---|---|
| Nosy | @birkenfeld, @rhettinger |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = 'https://github.com/rhettinger'
closed_at = <Date 2009-02-23.19:40:08.891>
created_at = <Date 2009-02-23.13:37:11.058>
labels = ['docs']
title = 'Modification to "pairwise" in itertools recipes'
updated_at = <Date 2009-02-23.21:57:27.667>
user = 'https://bugs.python.org/della'bugs.python.org fields:
activity = <Date 2009-02-23.21:57:27.667>
actor = 'della'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2009-02-23.19:40:08.891>
closer = 'rhettinger'
components = ['Documentation']
creation = <Date 2009-02-23.13:37:11.058>
creator = 'della'
dependencies = []
files = []
hgrepos = []
issue_num = 5350
keywords = []
message_count = 7.0
messages = ['82626', '82627', '82630', '82638', '82640', '82641', '82646']
nosy_count = 4.0
nosy_names = ['georg.brandl', 'rhettinger', 'LambertDW', 'della']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue5350'
versions = []
Activity
della commentedon Feb 23, 2009
I feel that the "pairwise" recipe could be slightly more elegant if "for
elem in b: break" became a simpler next(b) (or b.next() for Python 2.x).
It is also more natural to modify the recipes to suit one's needs (e.g.,
returning items with a given gap between them, or convert the recipe to
k-wise iteration).
birkenfeld commentedon Feb 23, 2009
Assigning to Raymond.
Note that "for elem in b: break" and "next(b)" are not equivalent when b
is empty/exhausted.
della commentedon Feb 23, 2009
Georg, you're right, there's a StopIteration to catch. My thinko was
mistaking the function for a generator where the exception propagation
would have done the right thing. The amended version now becomes
...which is not that attractive anymore, also because it's slower. Sorry
for the error.
rhettinger commentedon Feb 23, 2009
Applied in r69908 .
lambertdw commentedon Feb 23, 2009
Nice. I had thought of this a while ago but found counter example,
probably using the empty iterator
I didn't realize "next" had optional argument.
birkenfeld commentedon Feb 23, 2009
Shame on me, I forgot about the optional argument too.
della commentedon Feb 23, 2009
great Raymond! :)