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add aiter() and anext() functions #76042
Description
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 = None
closed_at = <Date 2021-03-24.01:43:07.674>
created_at = <Date 2017-10-24.13:26:15.573>
labels = ['library', '3.10']
title = 'add aiter() and anext() functions'
updated_at = <Date 2021-04-07.22:59:05.539>
user = 'https://github.com/sorcio'bugs.python.org fields:
activity = <Date 2021-04-07.22:59:05.539>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2021-03-24.01:43:07.674>
closer = 'pablogsal'
components = ['Library (Lib)']
creation = <Date 2017-10-24.13:26:15.573>
creator = 'davide.rizzo'
dependencies = []
files = ['47242']
hgrepos = []
issue_num = 31861
keywords = ['patch']
message_count = 25.0
messages = ['304910', '304923', '304924', '304926', '305107', '319519', '319520', '323989', '323997', '324009', '337061', '337135', '375633', '380408', '381832', '383327', '383441', '389414', '389417', '389420', '389422', '389426', '389427', '390402', '390495']
nosy_count = 15.0
nosy_names = ['gvanrossum', 'vstinner', 'rb', 'jab', 'davide.rizzo', 'jmehnle', 'Dima.Tisnek', 'yselivanov', 'JelleZijlstra', 'pablogsal', 'BTaskaya', 'Eric Wieser', 'John Belmonte', 'jack1142', 'Dennis Sweeney']
pr_nums = ['8895', '23847', '25004', '25005', '25008']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue31861'
versions = ['Python 3.10']
Activity
sorcio commentedon Oct 24, 2017
PEP-525 suggested that adding aiter() and anext() would need to wait until async __aiter__ is dropped in 3.7. bpo-31709 solved that, so now it would be possible to add them.
1st1 commentedon Oct 24, 2017
Guido, do we need a PEP to add aiter() and anext() builtins?
gvanrossum commentedon Oct 24, 2017
No, just this tracker issue, a PR and a reviewer. (Sorry, I can't review
CPython code myself any more.)
1st1 commentedon Oct 24, 2017
Alright, I'll work on a PR after PEP 55x.
sorcio commentedon Oct 27, 2017
I attempted to make a Python implementation (attached) to use in my code. There are a few questions in the comments.
One of the complications is the async equivalent of next with two arguments like next(iterator, default). It cannot return the result of __anext__() because it needs to catch StopAsyncIteration. So it should return an awaitable wrapper instead (in my Python code this is rendered as a coroutine). A secondary question is whether the default value should be returned as it is passed, or awaited on.
JelleZijlstra commentedon Jun 14, 2018
Do these really need to be builtins?
They seem too specialized to be widely useful; I've personally never needed them in any async code I've written. It would make more sense to me to put them in a module like operators.
1st1 commentedon Jun 14, 2018
We're only beginning to see async iterators being used in the wild, so we can't have a definitive answer at this point.
I think putting them to the operators module makes sense, at least for 3.8. Do you want to work on a pull request?
jab commentedon Aug 24, 2018
Updating the issue title to reflect the decision to add these to the operator module rather than to built-ins.
Submitted a PR here: #8895
[-]aiter() and anext() built-in functions[/-][+]add aiter() and anext() functions to operator module[/+]1st1 commentedon Aug 24, 2018
Great, thanks! There's someone working on a pr to add them as builtins (so that pr is in C). I'll have to take a look when i'm back from vacation at that pr too, before we can make a decision.
I've been to europython, pycon ru, and pybay conferences recently and the number of people who want these as builtins was surprisingly high.
jab commentedon Aug 24, 2018
Interesting, thanks Yury!
I only saw the discussion here which implied these wouldn't go directly into builtins for 3.8 (and I searched here and in GitHub, and couldn't find the PR you mentioned either), so I'm curious if that was tracked somewhere. It'd be unfortunate if the work I did on that PR couldn't be used, but I'd be even happier to have these as builtins.
Thanks again for reviewing when you're back, and have a wonderful vacation in the meantime!
dimaqq commentedon Mar 4, 2019
https://www.python.org/dev/peps/pep-0525/#aiter-and-anext-builtins kinda promised
aiterandanextbuilt-ins.This ticket seems idle.
Perhaps it's time for the decider club to either remove that language from PEP-525 or make a plan for aiter/anext?
7 remaining items
jab commentedon Dec 18, 2020
Please see #23847 for the C implementation of aiter and anext added to builtins, as requested.
[-]add aiter() and anext() functions to operator module[/-][+]add aiter() and anext() functions[/+]isidentical commentedon Dec 20, 2020
I don't have anything to add to this beside the name choice is safe and won't clash with anything (but honestly I would prefer it to be discussed on the ML before implementing something after 3 years). I checked a limited dataset to search for aiter and only found examples from 2 different projects. Elastic have something for themselves and the other usages are coming from the tests of aioitertools.
https://github.com/elastic/elasticsearch-py/blob/5fe9ff721ce493fbf2fc8b94d5ab02fc7e55fd5a/elasticsearch/_async/helpers.py#L85-L96
gvanrossum commentedon Mar 23, 2021
New changeset f0a6fde by Joshua Bronson in branch 'master':
bpo-31861: Add aiter and anext to builtins (bpo-23847)
f0a6fde
pablogsal commentedon Mar 23, 2021
New changeset d969202 by Pablo Galindo in branch 'master':
bpo-31861: Complete the C-API docs for PyObject_GetAiter and PyAiter_Check (GH-25004)
d969202
pablogsal commentedon Mar 24, 2021
New changeset 919d42d by Pablo Galindo in branch 'master':
bpo-31861: Fix possible crash in PyAnextAwaitable_New (GH-25005)
919d42d
vstinner commentedon Mar 24, 2021
I reopen the issue.
The commit f0a6fde introduced a reference leak:
$ ./python -m test -R 3:3 test_asyncgen0:00:00 load avg: 4.75 Run tests sequentially
0:00:00 load avg: 4.75 [1/1] test_asyncgen
beginning 6 repetitions
123456
......
test_asyncgen leaked [72, 72, 72] references, sum=216
test_asyncgen leaked [30, 30, 30] memory blocks, sum=90
test_asyncgen failed
== Tests result: FAILURE ==
1 test failed:
test_asyncgen
Total duration: 6.0 sec
Tests result: FAILURE
pablogsal commentedon Mar 24, 2021
New changeset a02683a by Pablo Galindo in branch 'master':
bpo-31861: Fix reference leak in builtin_anext_impl() (GH-25008)
a02683a
pablogsal commentedon Mar 24, 2021
Fixed by PR25008
sweeneyde commentedon Apr 7, 2021
A bug was reported in anext(): https://bugs.python.org/issue43751
vstinner commentedon Apr 7, 2021
I proposed to PR 25266 to rename PyAnextAwaitable_Type to _PyAnextAwaitable_Type, and to initialize the type at Python startup: can someone please have a look?