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Add subprocess.iter_output() convenience function #57787

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ncoghlan opened this issue Dec 11, 2011 · 3 comments
Open

Add subprocess.iter_output() convenience function #57787

ncoghlan opened this issue Dec 11, 2011 · 3 comments
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stdlib Python modules in the Lib dir type-feature A feature request or enhancement

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@ncoghlan
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BPO 13578
Nosy @ncoghlan, @giampaolo

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 = None
created_at = <Date 2011-12-11.05:05:54.306>
labels = ['type-feature', 'library']
title = 'Add subprocess.iter_output() convenience function'
updated_at = <Date 2012-06-12.12:00:10.774>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2012-06-12.12:00:10.774>
actor = 'ncoghlan'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2011-12-11.05:05:54.306>
creator = 'ncoghlan'
dependencies = []
files = []
hgrepos = []
issue_num = 13578
keywords = []
message_count = 3.0
messages = ['149210', '149215', '152794']
nosy_count = 3.0
nosy_names = ['ncoghlan', 'giampaolo.rodola', 'rosslagerwall']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue13578'
versions = ['Python 3.4']
@ncoghlan
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subprocess.check_output() is nice, but doesn't help if you want to process the piped data line-by-line.

Currently, that means you have to do the full Popen dance if you want access to each line of output as it becomes available.

This RFE is for a subprocess.iter_output() module level helper that:

  1. Starts the subprocess
  2. Yield the individual lines of output as they are produced by the subprocess
  3. Cleans up (including checking for errors) at the end

This biggest challenge I have noticed so far in exploring this is how to handle timeouts on Windows - on Unix, select.select() can do the job, but that won't handle pipes in the Windows case.

@ncoghlan ncoghlan added stdlib Python modules in the Lib dir type-feature A feature request or enhancement labels Dec 11, 2011
@ncoghlan
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You can see a version of this here:

https://bitbucket.org/ncoghlan/shell_command/src/2b1988b072aa/shell_command.py#cl-157

@giampaolo
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This biggest challenge I have noticed so far in exploring
this is how to handle timeouts on Windows

I haven't actually looked into it but this somewhat recalls:
http://bugs.python.org/issue1191964
Since bpo-1191964 is supposed to provide async subprocess I/O I presume Windows timeouts are also involved somewhere in the provided patch/recipe.

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