Make contextlib.redirect_stdout reentrant

[ncoghlan]

BPO	19403
Nosy	@rhettinger, @ncoghlan
Dependencies	bpo-19330: Use public classes for contextlib.suppress and redirect_stdout
Files	issue19403_reentrant_redirect_stdout.diff: Make redirect_stdout reentrant

^{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 = 'https://github.com/ncoghlan'
closed_at = <Date 2013-11-03.07:02:23.977>
created_at = <Date 2013-10-26.06:43:50.540>
labels = ['type-feature']
title = 'Make contextlib.redirect_stdout reentrant'
updated_at = <Date 2013-11-03.07:02:23.975>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2013-11-03.07:02:23.975>
actor = 'python-dev'
assignee = 'ncoghlan'
closed = True
closed_date = <Date 2013-11-03.07:02:23.977>
closer = 'python-dev'
components = []
creation = <Date 2013-10-26.06:43:50.540>
creator = 'ncoghlan'
dependencies = ['19330']
files = ['32375']
hgrepos = []
issue_num = 19403
keywords = ['patch']
message_count = 4.0
messages = ['201318', '201358', '201514', '202001']
nosy_count = 3.0
nosy_names = ['rhettinger', 'ncoghlan', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue19403'
versions = ['Python 3.4']

[ncoghlan]

I realised making contextlib.redirect_stdout reentrant was actually fairly easy (thread safety is inherently impossible due to the process global side effect). Since making it reentrant makes it more user-friendly, I'll tweak the implementation to work that way.

Need to resolve bpo-19330 first, though.

As part of this change, the reusable-but-not-reentrant example in the docs needs to be updated to use contextlib.ExitStack rather than this (that's inherently not reentrant, since all the context managers in the stack would be triggered when the innermost context ends).

[ncoghlan]

I think this change also makes for nicer examples of reentrant (using the updated redirect_stdout) and reusable-but-not-reentrant (using ExitStack) behaviour in the docs.

[rhettinger]

+1

[python-dev]

New changeset 87d49e2cdd34 by Nick Coghlan in branch 'default':
Close bpo-19403: make contextlib.redirect_stdout reentrant
http://hg.python.org/cpython/rev/87d49e2cdd34