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

@bitdancer

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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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']

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?

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

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.

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.

Added a PR to facilitate discussion on python-ideas.

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

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

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

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Please add argument to override stdin/out/err in the input builtin #75784

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Please add argument to override stdin/out/err in the input builtin #75784

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wt commented on Sep 27, 2017

wt commented on Sep 27, 2017

bitdancer commented on Sep 27, 2017

serhiy-storchaka commented on Sep 27, 2017

wt commented on Sep 29, 2017

csabella commented on Mar 18, 2019

tonybaloney commented on May 6, 2019

iritkatriel commented on Jan 17, 2022

wt commented on Jan 20, 2022

iritkatriel commented on Oct 29, 2022

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