Issue 20423: io.StringIO newline param has wrong default (original) (raw)
Created on 2014-01-28 19:24 by couplewavylines, last changed 2022-04-11 14:57 by admin. This issue is now closed.
Messages (7)
Author: (couplewavylines)
Date: 2014-01-28 19:24
In io.StringIO, the newline argument's default is currently documented as "newline=None" in the section header. However, it's described this way: "The default is to do no newline translation." The behavior of io.StringIO is consistent with this description (NO newline translation). The header should actually read "newline=''". "newline=None" would mean there IS newline translation by default, which is not the case. Code sample attached as no_translation.py.
Author: Serhiy Storchaka (serhiy.storchaka) * 
Date: 2014-01-28 19:37
No, actual default is '\n'.
io.StringIO('abc\r\ndef\nghi\rklm').readlines() ['abc\r\n', 'def\n', 'ghi\rklm'] io.StringIO('abc\r\ndef\nghi\rklm', newline=None).readlines() ['abc\n', 'def\n', 'ghi\n', 'klm'] io.StringIO('abc\r\ndef\nghi\rklm', newline='').readlines() ['abc\r\n', 'def\n', 'ghi\r', 'klm'] io.StringIO('abc\r\ndef\nghi\rklm', newline='\n').readlines() ['abc\r\n', 'def\n', 'ghi\rklm'] io.StringIO('abc\r\ndef\nghi\rklm', newline='\r').readlines() ['abc\r', '\r', 'def\r', 'ghi\r', 'klm'] io.StringIO('abc\r\ndef\nghi\rklm', newline='\r\n').readlines() ['abc\r\r\n', 'def\r\n', 'ghi\rklm']
Author: (couplewavylines)
Date: 2014-01-28 19:44
Serhiy, you're right, I now see the default behavior is "newline='\n'".
So, the header is still wrong, and the text is "The default is to do no newline translation" may be incorrect too? Or just unclear (to me anyway)?
Author: Serhiy Storchaka (serhiy.storchaka) *
Date: 2014-01-28 19:51
On other hand, may be the behavior of io.StringIO is wrong. Because it is different from io.TextIOWrapper.
io.TextIOWrapper(io.BytesIO(b'abc\r\ndef\nghi\rklm')).readlines() ['abc\n', 'def\n', 'ghi\n', 'klm'] io.TextIOWrapper(io.BytesIO(b'abc\r\ndef\nghi\rklm'), newline=None).readlines() ['abc\n', 'def\n', 'ghi\n', 'klm'] io.TextIOWrapper(io.BytesIO(b'abc\r\ndef\nghi\rklm'), newline='').readlines() ['abc\r\n', 'def\n', 'ghi\r', 'klm'] io.TextIOWrapper(io.BytesIO(b'abc\r\ndef\nghi\rklm'), newline='\n').readlines() ['abc\r\n', 'def\n', 'ghi\rklm'] io.TextIOWrapper(io.BytesIO(b'abc\r\ndef\nghi\rklm'), newline='\r').readlines() ['abc\r', '\ndef\nghi\r', 'klm'] io.TextIOWrapper(io.BytesIO(b'abc\r\ndef\nghi\rklm'), newline='\r\n').readlines() ['abc\r\n', 'def\nghi\rklm']
Author: Antoine Pitrou (pitrou) *
Date: 2014-01-28 21:42
Using '\n' as default is normal: StringIOs are not stored on disk so there's no point in converting newlines by default (it's only slower while not improving interoperability). '\n' is the default line separator in Python.
So we should just fix the docs here.
The bug when using '\r' or '\r\n' should probably be fixed though (that would be a separate issue).
Author: Roundup Robot (python-dev) 
Date: 2014-02-02 21:51
New changeset 82cfab2ad98d by Antoine Pitrou in branch '3.3': Issue #20423: fix documentation of io.StringIO's newline parameter http://hg.python.org/cpython/rev/82cfab2ad98d
New changeset 69a2cc048c80 by Antoine Pitrou in branch '2.7': Issue #20423: fix documentation of io.StringIO's newline parameter http://hg.python.org/cpython/rev/69a2cc048c80
New changeset df2efd48227e by Antoine Pitrou in branch 'default': Issue #20423: fix documentation of io.StringIO's newline parameter http://hg.python.org/cpython/rev/df2efd48227e
Author: Antoine Pitrou (pitrou) *
Date: 2014-02-02 21:52
The docs are now fixed, thank you!
History
Date
User
Action
Args
2022-04-11 14:57:57
admin
set
github: 64622
2014-02-02 21:52:34
pitrou
set
status: open -> closed
resolution: fixed
messages: +
stage: needs patch -> resolved
2014-02-02 21:51:52
python-dev
set
nosy: + python-dev
messages: +
2014-01-28 21:42:10
pitrou
set
messages: +
2014-01-28 19:51:04
serhiy.storchaka
set
nosy: + pitrou, benjamin.peterson, stutzbach, hynek
messages: +
2014-01-28 19:44:20
couplewavylines
set
messages: +
2014-01-28 19:37:23
serhiy.storchaka
set
versions: + Python 2.7
nosy: + serhiy.storchaka
messages: +
keywords: + easy
stage: needs patch
2014-01-28 19:26:20
couplewavylines
set
files: + no_translation_output.txt
2014-01-28 19:24:38
couplewavylines
create