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OrderedDict iterators are exhausted during pickling #78755

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sir-sigurd mannequin opened this issue Sep 4, 2018 · 7 comments
Closed

OrderedDict iterators are exhausted during pickling #78755

sir-sigurd mannequin opened this issue Sep 4, 2018 · 7 comments
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@serhiy-storchaka
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3.7 (EOL) end of life 3.8 only security fixes extension-modules C modules in the Modules dir type-bug An unexpected behavior, bug, or error

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@sir-sigurd
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sir-sigurd mannequin commented Sep 4, 2018

BPO 34574
Nosy @serhiy-storchaka, @MojoVampire, @sir-sigurd, @miss-islington, @tirkarthi
PRs
  • bpo-34574: Prevent OrderedDict iterators from exhaustion during pickling. #9051
  • [3.7] bpo-34574: Prevent OrderedDict iterators from exhaustion during pickling. (GH-9051) #9996
  • [3.6] bpo-34574: Prevent OrderedDict iterators from exhaustion during pickling. (GH-9051) #9997
    		•

    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/serhiy-storchaka'
closed_at = <Date 2018-10-20.06:06:46.626>
created_at = <Date 2018-09-04.04:19:39.374>
labels = ['extension-modules', '3.8', 'type-bug', '3.7']
title = 'OrderedDict iterators are exhausted during pickling'
updated_at = <Date 2018-10-20.06:06:46.548>
user = 'https://github.com/sir-sigurd'

    bugs.python.org fields:

    activity = <Date 2018-10-20.06:06:46.548>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2018-10-20.06:06:46.626>
closer = 'serhiy.storchaka'
components = ['Extension Modules']
creation = <Date 2018-09-04.04:19:39.374>
creator = 'sir-sigurd'
dependencies = []
files = []
hgrepos = []
issue_num = 34574
keywords = ['patch']
message_count = 7.0
messages = ['324551', '324650', '324664', '328124', '328126', '328127', '328128']
nosy_count = 5.0
nosy_names = ['serhiy.storchaka', 'josh.r', 'sir-sigurd', 'miss-islington', 'xtreak']
pr_nums = ['9051', '9996', '9997']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue34574'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']
    @sir-sigurd
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    sir-sigurd mannequin commented Sep 4, 2018

    In [1]: from collections import OrderedDict

    In [2]: od = OrderedDict.fromkeys(range(10))

    In [3]: it = iter(od)

    In [4]: it.__reduce__()
    Out[4]: (<function iter>, ([0, 1, 2, 3, 4, 5, 6, 7, 8, 9],))

    In [5]: list(it)
    Out[5]: []

    @sir-sigurd sir-sigurd mannequin added the type-bug An unexpected behavior, bug, or error label Sep 4, 2018
    @MojoVampire
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    MojoVampire mannequin commented Sep 5, 2018

    This would presumably be a side-effect of all generic pickling operations of iterators; figuring out what the iterator produces requires running out the iterator. You could special case it case-by-case, but that just makes the behavior unreliable/confusing; now some iterators pickle without being mutated, and others don't. Do you have a proposal to fix it? Is it something that needs to be fixed at all, when the option to pickle the original OrderedDict directly is there?

    @sir-sigurd
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    sir-sigurd mannequin commented Sep 6, 2018

    Other iterators either don't support pickling or aren't mutated during pickling:

    In [10]: it = iter({1})

    In [11]: pickle.dumps(it)
    Out[11]: b'\x80\x04\x95\x1e\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x04iter\x94\x93\x94]\x94K\x01a\x85\x94R\x94.'

    In [12]: list(it)
    Out[12]: [1]

    In [13]: it = (x for x in {1})

    In [14]: pickle.dumps(it)
    ---------------------------------------------------------------------------

    TypeError                                 Traceback (most recent call last)
<ipython-input-14-7e86a183a31c> in <module>()
----> 1 pickle.dumps(it)

    TypeError: can't pickle generator objects

    @serhiy-storchaka serhiy-storchaka self-assigned this Sep 8, 2018
    @serhiy-storchaka
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    New changeset a5259fb by Serhiy Storchaka (Sergey Fedoseev) in branch 'master':
    bpo-34574: Prevent OrderedDict iterators from exhaustion during pickling. (GH-9051)
    a5259fb

    @miss-islington
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    New changeset dcd56f6 by Miss Islington (bot) in branch '3.7':
    bpo-34574: Prevent OrderedDict iterators from exhaustion during pickling. (GH-9051)
    dcd56f6

    @miss-islington
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    New changeset 0d3dd9f by Miss Islington (bot) in branch '3.6':
    bpo-34574: Prevent OrderedDict iterators from exhaustion during pickling. (GH-9051)
    0d3dd9f

    @serhiy-storchaka
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    Thank your Sergey for your report and fix.

    @serhiy-storchaka serhiy-storchaka added extension-modules C modules in the Modules dir 3.7 (EOL) end of life 3.8 only security fixes labels Oct 20, 2018
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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