[docs] [issue26897] Clarify Popen stdin, stdout, stderr

[Yclept Nemo]

New submission from Yclept Nemo:

From: https://docs.python.org/dev/library/subprocess.html#popen-constructor

"..., an existing file descriptor (a positive integer), an existing file object, and None."

It should be made clear that the file object must be backed by an operating system file, i.e. must have a valid file descriptor.

As it stands, the documentation suggests implicit concurrency: that any file object can be used, and on read/write from the subprocess/OS arbitrary python code will be executed, i.e. the python interpreter is pre-empted or python spawns a hidden I/O thread.

Anyway, I'm pretty sure subprocess.Popen() just redirects the forked process' stdout/stdin/stderr to the file descriptors from the provided file object.

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assignee: docs at python
components: Documentation
messages: 264579
nosy: Yclept.Nemo, docs at python
priority: normal
severity: normal
status: open
title: Clarify Popen stdin, stdout, stderr
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26897>
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