Please add argument to override stdin/out/err in the input builtin

[wt]

BPO	31603
Nosy	@bitdancer, @wt, @serhiy-storchaka, @csabella, @tonybaloney, @iritkatriel
PRs	bpo-31603 Add file args to input builtin #3814

^{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 2017-09-27.06:34:07.094>
labels = ['3.7', 'expert-IO']
title = 'Please add argument to override stdin/out/err in the input builtin'
updated_at = <Date 2022-01-20.18:29:21.436>
user = 'https://github.com/wt'

bugs.python.org fields:

activity = <Date 2022-01-20.18:29:21.436>
actor = 'wt'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['IO']
creation = <Date 2017-09-27.06:34:07.094>
creator = 'wt'
dependencies = []
files = []
hgrepos = []
issue_num = 31603
keywords = ['patch']
message_count = 9.0
messages = ['303103', '303105', '303132', '303135', '303297', '338208', '341587', '410816', '411041']
nosy_count = 6.0
nosy_names = ['r.david.murray', 'wt', 'serhiy.storchaka', 'cheryl.sabella', 'anthonypjshaw', 'iritkatriel']
pr_nums = ['3814']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue31603'
versions = ['Python 3.7']

[wt]

I would really love to add a few params to input so that it's signature looked more like so:

def input(prompt, /, *, fin=sys.stdin, fout=sys.stdout, ferr=sys.stderr):
    ...

This would certainly make overriding the the files in specific calls to input easier. A reasonable use case is collecting a piece over /dev/tty explicitly so that a redirected stdin could be used to pipe data into a program while overriding using /dev/tty to collect some piece of data. Here's some code illustrating what I'd like:

import sys
sys.stdin.close()
sys.stdin = open('/dev/null', 'r')
with open('/dev/tty', 'r') as f:
    x = input('Name? ', fin=f)
print(x)

FWIW, I have actually already implemented this fully (including tests). I am just trying to see what I need to do to allow release since I am work on my employer's time.

In the interest of getting feedback, does the signature provided above look sane?

[wt]

This might also allow simplification of the getpass.unix_getpass() logic. I am not 100% sure about that yet though.

[bitdancer]

This is probably a topic for the python-ideas mailing list. For example, rather than complicating input, it might be better to propose adding a redirect_stdin to contextlib to parallel the two existing redirect context managers. I don't remember why that was not added when the others were, but there was probably a reason, so a discussion about what the best solution is for the use case is in order, and python-ideas is the place for that.

[serhiy-storchaka]

input() is a convenient function for simple user interaction. If you need to read a data from different file object just use its readline() method.

[wt]

Added a PR to facilitate discussion on python-ideas.

[csabella]

For reference, here's the link to the Python ideas thread:

https://mail.python.org/pipermail/python-ideas/2017-September/047230.html

[tonybaloney]

The discussion on python-ideas has some unresolved questions. Wren, did you get a definitive answer on this idea?

[iritkatriel]

See also bpo-1927.

[wt]

I'm not sure that I ever got a definitive issue, but I didn't have time to
push it forward. I still think the idea has merit. I'd love to see it
implemented, but I don't have the time to pursue it right now.

Thanks,
wt

On Mon, Jan 17, 2022 at 10:23 AM Irit Katriel <report@bugs.python.org>
wrote:

Irit Katriel <iritkatriel@gmail.com> added the comment:

See also bpo-1927.

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nosy: +iritkatriel

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Python tracker <report@bugs.python.org>
<https://bugs.python.org/issue31603\>

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[iritkatriel]

[...] I don't have the time to pursue it right now.

Thanks, wt

Thank you.