Remove array.fromstring() and array.tostring() aliases, deprecated since Python 3.2

[corona10]

BPO	38916
Nosy	@brettcannon, @rhettinger, @vstinner, @benjaminp, @serhiy-storchaka, @corona10, @miss-islington
PRs	bpo-38916: array.array: remove fromstring() and tostring() #17487 [3.8] bpo-38916: Document array.array deprecation #17523 [3.7] bpo-38916: Document array.array deprecation (GH-17523) #17525

^{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 2019-12-09.13:58:48.548>
created_at = <Date 2019-11-26.14:08:48.341>
labels = ['easy', 'library', '3.9']
title = 'Remove array.fromstring() and array.tostring() aliases, deprecated since Python 3.2'
updated_at = <Date 2019-12-09.13:58:48.547>
user = 'https://github.com/corona10'

bugs.python.org fields:

activity = <Date 2019-12-09.13:58:48.547>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-12-09.13:58:48.548>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2019-11-26.14:08:48.341>
creator = 'corona10'
dependencies = []
files = []
hgrepos = []
issue_num = 38916
keywords = ['patch', 'easy (C)']
message_count = 17.0
messages = ['357495', '357496', '357497', '357524', '357527', '357538', '357576', '357601', '357623', '357932', '357933', '357941', '358072', '358073', '358084', '358087', '358089']
nosy_count = 7.0
nosy_names = ['brett.cannon', 'rhettinger', 'vstinner', 'benjamin.peterson', 'serhiy.storchaka', 'corona10', 'miss-islington']
pr_nums = ['17487', '17523', '17525']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue38916'
versions = ['Python 3.9']

[corona10]

array.fromstring was deprecated at 3.2

IMHO, now we can remove array.fromstring.
For my research, there is no usage on the standard library.
I 'd like to propose that let's remove array.fromstring from 3.9

[corona10]

I'd like to tag this issue as an easy issue.

[corona10]

For whom are interested in this issue,
Please wait until the core developer decides to approve this issue. :)
After that, we can review the PR for this issue.

Thank you for understanding.

[brettcannon]

If it was documented as deprecated and raising a deprecation warning then 3.2 is definitely far enough back to warrant removing it.

[brettcannon]

Although I will admit we have not had a discussion on python-dev about removing stuff that was left for Python 2.7 compatibility, so that discussion should probably occur first before we go ripping stuff out.

[rhettinger]

Thoughts:

• The tostring() method should be handled in the same way.
• Remediation is easy because from_bytes() is a alias
• Still, all removals cause disruption from at least some users
• The only real benefit of removing it is a sense of tidiness;
  otherwise, there's no harm to keeping it (it's not broken).
• The other deprecation in the array module says, "Deprecated since
  version 3.3, will be removed in version 4.0". Perhaps this
  one should have had the same qualifier.

[brettcannon]

there's no harm to keeping it (it's not broken)

... for now. :) There's always the risk that will change if we keep the code around.

The other deprecation in the array module says, "Deprecated since version 3.3, will be removed in version 4.0". Perhaps this one should have had the same qualifier.

If the function is left then I agree it should probably be updated to match the rest of the module.

[corona10]

The other deprecation in the array module says, "Deprecated since version 3.3, will be removed in version 4.0". Perhaps this one should have had the same qualifier.

I agree,
How about note it in the documentation and logging rather than removing them?

[brettcannon]

How about note it in the documentation and logging rather than removing them?

Yep, docs and raising DeprecationWarning should be good.

[vstinner]

If it was documented as deprecated and raising a deprecation warning then 3.2 is definitely far enough back to warrant removing it.

Exactly. I'm in favor of removing fromstring() and tostring() methods right now, and update 3.7 and 3.8 documentation to mention that the methods are removed in Python 3.9, not Python 4.0.

Either do it right now, or wait the beginning of the next Python 3.x release cycle. I prefer to push some incompatible changes at the beginning of dev cycles, to get enough time to measure the feedback from users.

--

Brett opened a more generic discussion about the deprecation process, since PEP-602 has been accepted:
https://mail.python.org/archives/list/python-dev@python.org/thread/BRA7G4UIGGW2X7YY55KQZBOGJEYNUV6O/

[vstinner]

I chose to write PR 17487 even if the issue was tagged as "easy (C)", just to make sure that the change is done as soon as possible in the 3.9 dev cycle.

[vstinner]

bpo-38897 removed usage of deprecated array.fromstring() method. Commit in master:

386d00c

[vstinner]

New changeset 0131aba by Victor Stinner in branch 'master':
bpo-38916: array.array: remove fromstring() and tostring() (GH-17487)
0131aba

[vstinner]

Brett Cannon: "If it was documented as deprecated and raising a deprecation warning then 3.2 is definitely far enough back to warrant removing it."

I understood that Brett is in favor of removing it.

Raymond Hettinger: "The tostring() method should be handled in the same way."

Done.

Raymond Hettinger: "Remediation is easy because from_bytes() is a alias"

For code supporting Python 2 and Python 3, it may be annoying, but Python 3.9 will only be released after Python 2 support will end. So I consider that it's an acceptable annoyance. Users can put "if six.PY3" in their code or don't support Python 3.9.

Raymond Hettinger: "Still, all removals cause disruption from at least some users"

I'm perfectly aware of that. But I consider that it's worth it. I chose to push my change early in the 3.9 development cycle, to get users feedback earlier. So we can still revert the change if they are too many complains.

Raymond Hettinger: "The other deprecation in the array module says, "Deprecated since version 3.3, will be removed in version 4.0". Perhaps this one should have had the same qualifier."

I proposed PR 17523 to document that tostring() and fromstring() deprecated aliases will be removed in Python 3.9.

[vstinner]

New changeset 0381ea7 by Victor Stinner in branch '3.8':
bpo-38916: Document array.array deprecation (GH-17523)
0381ea7

[miss-islington]

New changeset 21e1138 by Miss Islington (bot) in branch '3.7':
bpo-38916: Document array.array deprecation (GH-17523)
21e1138

[vstinner]

The aliases were deprecated since Python 3.2. It's now time to use the newer names.

array.array.fromstring() implictly converted Unicode to UTF-8:

$ python3
Python 3.7.5 (default, Oct 17 2019, 12:16:48) 
>>> import array
>>> a=array.array('B')
>>> a.fromstring('€uro')
>>> a
array('B', [226, 130, 172, 117, 114, 111])
>>> list('€uro'.encode('utf8'))
[226, 130, 172, 117, 114, 111]

The removal is now documented in 3.7 and 3.8.