Description

assignee = None
closed_at = None
created_at = <Date 2008-08-26.15:57:45.065>
labels = ['3.11', 'type-bug', '3.9', '3.10', 'docs']
title = 'Popen() object stdout attribute reassignment behaviour'
updated_at = <Date 2021-12-05.15:57:52.556>
user = 'https://bugs.python.org/vincentlegoll'

activity = <Date 2021-12-05.15:57:52.556>
actor = 'iritkatriel'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2008-08-26.15:57:45.065>
creator = 'vincent.legoll'
dependencies = []
files = []
hgrepos = []
issue_num = 3687
keywords = []
message_count = 5.0
messages = ['71983', '107970', '107976', '281545', '407713']
nosy_count = 7.0
nosy_names = ['georg.brandl', 'terry.reedy', 'giampaolo.rodola', 'vlegoll', 'vincent.legoll', 'maaz92', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue3687'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Activity

1. vincentlegoll commented on Aug 26, 2008

   

   vincentlegollmannequin

   on Aug 26, 2008

   MannequinAuthor

   More actions

   The subprocess.Popen() object documentation should indicate
   that the stdout attribute should not be modified after
   object construction. Because that won't work.

   Or the attribute may be rendered read-only

   >> from subprocess import Popen, PIPE
   >> import sys, os
   >> p1 = Popen(["echo", "1"], stdout = PIPE)
   >> p2 = Popen(["cat"], stdin = p1.stdout, stderr = PIPE, stdout = PIPE)
   >> p2.stdout = sys.stdout
   >> print p2.communicate()

   This blocks forever
2. vincentlegoll

   assigned

   birkenfeld

   on Aug 26, 2008
3. vincentlegoll

   added

   docsDocumentation in the Doc dirDocumentation in the Doc dir

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Aug 26, 2008
4. terryjreedy commented on Jun 17, 2010

   

   terryjreedy

   on Jun 17, 2010

   Member

   More actions

   While it could be argued that it is 'obvious' that changing the stdin, stdout, stderr, and pid of a processes cannot work, I agree that a small addition would be good. In 17.1.2. Popen Objects, after "The following attributes are also available", insert " (do not try to change them)" before ':'.

   Actually, it seems to me that the attributes should actually be read-only (in 3.2) if possible (via custom Popen.__setattr__), in which case the only doc change needed (for 3.2) would be insertion of 'read-only' before 'attributes'.

   Georg, if you know the id of the subprocess maintainer (if there is one now), could you add him to the nosy list for an opinion or comment?
5. vlegoll commented on Jun 17, 2010

   

   vlegollmannequin

   on Jun 17, 2010

   Mannequin

   More actions

   On Thu, Jun 17, 2010 at 2:34 AM, Terry J. Reedy <[email protected]> wrote:

   While it could be argued that it is 'obvious'

   What is obvious for someone maybe is not for others, if I tried to modify it,
   that was on the (false) assumption that it will do what I wanted (whatever
   that is)...

   Adding more precision to documentation or making the interface fool proof
   will make life of dumb devs like me easier by not having to guess or try.

   Thanks for taking care of this.
6. admin

   assigned

   docspython

   and unassigned

   birkenfeld

   on Oct 29, 2010
7. maaz92 commented on Nov 23, 2016

   

   maaz92mannequin

   on Nov 23, 2016

   Mannequin

   More actions

   Hi, I want to update the doc for this. This will be my first attempt to update the documentation.
8. vadmium

   added

   3.7 (EOL)end of lifeend of life

   on Dec 6, 2016
9. iritkatriel commented on Dec 5, 2021

   

   iritkatriel

   on Dec 5, 2021

   Member

   More actions

   The situation is the same in 3.11, both doc and implementation.
10. iritkatriel

    added

    3.9 (EOL)end of lifeend of life

    3.10 (EOL)end of lifeend of life

    3.11only security fixesonly security fixes

    and removed

    3.7 (EOL)end of lifeend of life

    on Dec 5, 2021
11. ezio-melotti

    transferred this issue fromon Apr 10, 2022
12. iritkatriel

    added

    3.12only security fixesonly security fixes

    and removed

    3.9 (EOL)end of lifeend of life

    on Feb 2, 2023
13. gpshead

    added a commit that references this issue on Feb 8, 2023

    gh-47937: Note that Popen attributes are read-only (#93070)

    027adf4
14. miss-islington

    added 3 commits that reference this issue on Feb 8, 2023

    pythongh-47937: Note that Popen attributes are read-only (pythonGH-93070

    49398b8

    pythongh-47937: Note that Popen attributes are read-only (pythonGH-93070

    cc9e77c

    pythongh-47937: Note that Popen attributes are read-only (pythonGH-93070

    15e6490
15. gpshead

    closed this as completedon Feb 8, 2023
16. ambv

    added 2 commits that reference this issue on Feb 8, 2023

    [3.11] gh-47937: Note that Popen attributes are read-only (GH-93070) (#…

    7240ba7

    [3.10] gh-47937: Note that Popen attributes are read-only (GH-93070) (#…

    8bc4111
17. carljm

    added a commit that references this issue on Feb 9, 2023

    Merge branch 'main' into inlinecomp2

    be3becc

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