Deprecate the 'U' open mode #59409

serhiy-storchaka · 2012-06-27T10:29:51Z

BPO	15204
Nosy	@birkenfeld, @rhettinger, @pitrou, @bitdancer, @asvetlov, @cjerdonek, @vadmium, @serhiy-storchaka, @vajrasky
Files	deprecate-U-mode.patch deprecate-U-mode_2.patch deprecate-U-mode_3.patch

^{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 2013-11-24.21:15:30.677>
created_at = <Date 2012-06-27.10:29:50.642>
labels = ['type-bug', 'library', 'expert-IO', 'docs']
title = "Deprecate the 'U' open mode"
updated_at = <Date 2014-10-19.20:20:15.229>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2014-10-19.20:20:15.229>
actor = 'serhiy.storchaka'
assignee = 'docs@python'
closed = True
closed_date = <Date 2013-11-24.21:15:30.677>
closer = 'serhiy.storchaka'
components = ['Documentation', 'Library (Lib)', 'IO']
creation = <Date 2012-06-27.10:29:50.642>
creator = 'serhiy.storchaka'
dependencies = []
files = ['31416', '32708', '32809']
hgrepos = []
issue_num = 15204
keywords = ['patch']
message_count = 22.0
messages = ['164142', '164144', '164145', '164153', '164232', '164296', '168247', '171546', '171547', '171549', '179190', '195865', '195875', '203421', '203432', '204081', '204092', '204094', '204269', '213002', '229527', '229693']
nosy_count = 15.0
nosy_names = ['georg.brandl', 'rhettinger', 'pitrou', 'nadeem.vawda', 'stutzbach', 'Arfrever', 'r.david.murray', 'asvetlov', 'chris.jerdonek', 'docs@python', 'python-dev', 'martin.panter', 'serhiy.storchaka', 'vajrasky', '\xd0\x92\xd0\xb0\xd1\x81\xd0\xb8\xd0\xbb\xd0\xb8\xd0\xb9.\xd0\x9c\xd0\xb0\xd0\xba\xd0\xb0\xd1\x80\xd0\xbe\xd0\xb2']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue15204'
versions = ['Python 3.4']

serhiy-storchaka · 2012-06-27T10:29:50Z

Since Python 2.3 many open functions supports "Universal line mode" (PEP-278). Since 3.0 (and 2.6) PEP-3116 suggests better alternative -- io.TextWrapper.

Now support for the 'U' mode in the different open functions is heterogeneous. Some functions simply ignore the 'U' mode (but accept it), others perceive it as a synonym for text-mode, others just pass it on lower lever, other attempt to implement it, but the implementation is obtained imperfect and contradictory (as in ZipExtFile). The documentation for built-in open does not advise the use of the 'U' mode. The 'U' mode support cumbersome. I propose to deprecate the 'U' mode. If someone wanted to work with the universal line support, he'll surely need to work with encodings too, and io.TextWrapper provides is better choise.

The deprecation plan for the 'U' mode of open functions might be as follow:

3.3. Deprecating the 'U' mode in docs for all opens (building open, io.open, codecs.open, gzip.open, ZipFile.open, etc). Add suggestion about io.TextWrapper.
3.4. Raise a warning on use of the 'U' mode.
3.5. Raise an exception on use of the 'U' mode.
3.6 (or 4.0?). Remove the 'U' mode processing code.

As the first stage involves only the changes to the documentation, I hope deprecation can starts in 3.3.

serhiy-storchaka · 2012-06-27T10:50:57Z

Related issues: bpo-2091, bpo-5148, bpo-6759, bpo-12900.

pitrou · 2012-06-27T10:53:21Z

Starting to deprecate "U" in the 3.3 docs sounds reasonable to me.

bitdancer · 2012-06-27T13:31:01Z

Unless there are places where it is actually broken, I don't think there is a good reason to have step 3.5, though. Just add the deprecation warning and remove it in 4.0.

serhiy-storchaka · 2012-06-28T09:30:27Z

Unless there are places where it is actually broken, I don't think there is a good reason to have step 3.5, though. Just add the deprecation warning and remove it in 4.0.

Well. In any case, the 'U' mode in most cases has no effect, and the
code, where it has an effect (in zipfile), is very rarely used (and it
is actually complicated and broken).

Here are the patches for the first (documentation) and the second stage
(warnings).

nadeemvawda · 2012-06-28T21:28:35Z

+1 for the general idea of deprecating and eventually removing the "U"
modes.

But I agree with David, that it doesn't make sense to have separate steps
for 3.5 and 3.6/4.0. If you make the code raise an exception when "U" is
used, how is that different from what will happen when you remove the
code for processing it? Surely we want it to eventually be treated just
like any other invalid mode string?

rhettinger · 2012-08-15T00:41:15Z

The only people affected by deprecating "U" are the people who are currently using it for some reason -- presumably they are expecting that it does something useful for their code.

Ideally, this proposed deprecation should be mentioned on python-dev so that those folks will have an opportunity to respond.

serhiy-storchaka · 2012-09-28T21:59:29Z

Ideally, this proposed deprecation should be mentioned on python-dev so that those folks will have an opportunity to respond.

http://comments.gmane.org/gmane.comp.python.devel/134996

serhiy-storchaka · 2012-09-28T22:02:50Z

Chris, you did a great job on improving the documentation (including about universal newlines). Can you help with this issue?

For the first stage should be clearly shown that "U" mode is not only should not be used in new code, but must be removed from the old code.

Stage 1 patch updated to resolve conflicts with Chris changes.

cjerdonek · 2012-09-28T23:28:52Z

Thanks, Serhiy. :) Sure, I should be able to help with the documentation portion of this issue if the community is in agreement. Would the deprecation need to be moved up to 3.4 though now?

pitrou · 2013-01-06T15:48:27Z

Would the deprecation need to be moved up to 3.4 though now?

Yes, I think so.

serhiy-storchaka · 2013-08-22T07:27:08Z

Here is an updated patch. I think we can combine 1 and 2 stages (change the documentation and add warnings).

vajrasky · 2013-08-22T09:50:50Z

http://bugs.python.org/review/15204/diff/9032/Tools/iobench/iobench.py

Line 10 in New:
import io

But io module is never used.

serhiy-storchaka · 2013-11-19T20:38:37Z

Could anyone please review the patch?

serhiy-storchaka · 2013-11-19T21:58:10Z

Updated patch addresses Victor's comments.

serhiy-storchaka · 2013-11-23T19:47:19Z

Updated patch addresses Ezio's comments.

python-dev · 2013-11-23T20:13:14Z

New changeset 70bd6f7e013b by Serhiy Storchaka in branch 'default':
Issue bpo-15204: Deprecated the 'U' mode in file-like objects.
http://hg.python.org/cpython/rev/70bd6f7e013b

serhiy-storchaka · 2013-11-23T20:14:27Z

Thanks Victor and Ezio for the reviews.

python-dev · 2013-11-24T21:13:50Z

New changeset 694e2708b4a8 by Serhiy Storchaka in branch 'default':
Issue bpo-15204: Silence and check the 'U' mode deprecation warnings in tests.
http://hg.python.org/cpython/rev/694e2708b4a8

python-dev · 2014-03-10T01:35:02Z

New changeset 2d5544afb510 by R David Murray in branch 'default':
whatsnew: 'U' mode deprecation (bpo-15204).
http://hg.python.org/cpython/rev/2d5544afb510

ghost · 2014-10-16T12:53:09Z

open() documentation is probably broken a little now. Here is what one can see at the end of open() description:
"...
Deprecated since version 3.4, will be removed in version 4.0.

The 'U' mode."

Reader may assume open() function is what will be removed. Which is frightening :)

serhiy-storchaka · 2014-10-19T20:20:15Z

Please open new issue for this.

serhiy-storchaka assigned docspython Jun 27, 2012

serhiy-storchaka added docs Documentation in the Doc dir stdlib Python modules in the Lib dir topic-IO type-bug An unexpected behavior, bug, or error labels Jun 27, 2012

serhiy-storchaka closed this as completed Nov 24, 2013

ezio-melotti transferred this issue from another repository Apr 10, 2022

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Deprecate the 'U' open mode #59409

Deprecate the 'U' open mode #59409

serhiy-storchaka commented Jun 27, 2012

serhiy-storchaka commented Jun 27, 2012

serhiy-storchaka commented Jun 27, 2012

pitrou commented Jun 27, 2012

bitdancer commented Jun 27, 2012

serhiy-storchaka commented Jun 28, 2012

nadeemvawda mannequin commented Jun 28, 2012

rhettinger commented Aug 15, 2012

serhiy-storchaka commented Sep 28, 2012

serhiy-storchaka commented Sep 28, 2012

cjerdonek commented Sep 28, 2012

pitrou commented Jan 6, 2013

serhiy-storchaka commented Aug 22, 2013

vajrasky mannequin commented Aug 22, 2013

serhiy-storchaka commented Nov 19, 2013

serhiy-storchaka commented Nov 19, 2013

serhiy-storchaka commented Nov 23, 2013

python-dev mannequin commented Nov 23, 2013

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python-dev mannequin commented Nov 24, 2013

python-dev mannequin commented Mar 10, 2014

ghost commented Oct 16, 2014

serhiy-storchaka commented Oct 19, 2014

Deprecate the 'U' open mode #59409

Deprecate the 'U' open mode #59409

Comments

serhiy-storchaka commented Jun 27, 2012

serhiy-storchaka commented Jun 27, 2012

serhiy-storchaka commented Jun 27, 2012

pitrou commented Jun 27, 2012

bitdancer commented Jun 27, 2012

serhiy-storchaka commented Jun 28, 2012

nadeemvawda mannequin commented Jun 28, 2012

rhettinger commented Aug 15, 2012

serhiy-storchaka commented Sep 28, 2012

serhiy-storchaka commented Sep 28, 2012

cjerdonek commented Sep 28, 2012

pitrou commented Jan 6, 2013

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serhiy-storchaka commented Nov 19, 2013

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ghost commented Oct 16, 2014

serhiy-storchaka commented Oct 19, 2014