[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Changes by Antoine Pitrou :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Antoine Pitrou added the comment:


New changeset 3c2817b6884a5fcf792197203f3c26b157210607 by Antoine Pitrou in 
branch 'master':
Fix bpo-30526: Add TextIOWrapper.reconfigure() and a 
TextIOWrapper.write_through attribute (#1922)
https://github.com/python/cpython/commit/3c2817b6884a5fcf792197203f3c26b157210607


--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Changes by Antoine Pitrou :


--
pull_requests: +2002

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Antoine Pitrou added the comment:

Thanks. I'll produce an updated PR using reconfigure() for line_buffering and 
write_through.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Nick Coghlan]

Nick Coghlan added the comment:

Right, the request/requirement for in-place configuration changes arise from 
the fact the underlying buffer objects can't readily be shared, while makes 
swapping out the wrapper problematic if others may already have references to 
the original.

The "Don't do this implicitly in a library" admonition is then really the same 
one that applies to any unusual tinkering with global state (e.g. 
monkeypatching): you can definitely break things if you do it carelessly, so 
let the main application decide if and when global state updates are 
appropriate.


I do like "reconfigure()" as the API name, since that's then nicely amenable to 
expanding to all the settings supported by `open()` as concrete use cases 
arise. One thing we'll need to watch out for is the difference between "Leave 
this setting alone" and "Revert this setting to the global default".

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Antoine Pitrou added the comment:

Le 01/06/2017 à 12:41, Serhiy Storchaka a écrit :
> 
> First at all, I'm not sure that allowing to modify TextIOWrapper settings 
> after creation is a good idea. I would be feeling uncomfortable if the 
> third-party library changed the buffering or encoding settings of passed text 
> stream for its own needs, and this stream is sys.stdout.

Agreed that third-party libraries should not, but we're talking about
applications here.

> For example set f.line_buffering = False for performance and break your 
> logging. Creating a new TextIOWrapper for own needs looks safer.

Now you may have two TextIOWrappers alive wrapping the same buffered IO
object.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

First at all, I'm not sure that allowing to modify TextIOWrapper settings after 
creation is a good idea. I would be feeling uncomfortable if the third-party 
library changed the buffering or encoding settings of passed text stream for 
its own needs, and this stream is sys.stdout. For example set f.line_buffering 
= False for performance and break your logging. Creating a new TextIOWrapper 
for own needs looks safer. But changing the global state is the essential part 
of Nick's and your issues.

This could have long-term consequences, so it is worth to discuss the principle 
on the Python-Dev mailing list before applying the changes.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Changes by Antoine Pitrou :


--
stage:  -> patch review

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Antoine Pitrou added the comment:

I don't think those two issues need to be merged.  Setting line_buffering and 
write_through is almost trivial, while setting the encoding seems to take a 
significant amount of effort.

That said, I agree that a unified interface may be nice.  Perhaps a 
reconfigure(**kwargs) method?

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

This looks similar to issue15216 and may be merged with it. At least setting 
line_buffering and encoding should have unified interface. I see two 
possibilities of making this Pythonic:

* Make attributes writeable.

* Add a method (configure(), reopen(), or like) that takes new values as 
keyword arguments. This allows to change several attributes at a time.

--
nosy: +ncoghlan, serhiy.storchaka

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

Changes by Antoine Pitrou :


--
pull_requests: +1965

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue30526] Allow setting line_buffering on existing TextIOWrapper

[Antoine Pitrou]

New submission from Antoine Pitrou:

Currently, if you want to change the line buffering behaviour of standard 
streams, you can create a new stream and assign it to 
sys.{stdout,stderr,stdin}.  Unfortunately, it is common for references to the 
old streams to be stored in various places (such as logging configuration, or 
third-party libraries).  Replacing them all is probably a hopeless cause.  It 
would be much better if one could simply write `sys.stdout.line_buffering = 
True` and be done with it.

--
components: IO
messages: 294850
nosy: benjamin.peterson, pitrou, stutzbach
priority: normal
severity: normal
status: open
title: Allow setting line_buffering on existing TextIOWrapper
type: enhancement
versions: Python 3.7

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com