[Python-ideas] allow overriding files used for the input builtin

[Wren Turkal]

Hi there,


I have posted an idea for improvement with a PR of an implementation to https://bugs.python.org/issue31603.


The basic idea is to add fin, fout, and ferr file object parameters and default to using what is used today when the args are not specified. I believe this would be useful to allow captures input and send output to specific files when using input. The input builtin has some logic to use readline if it's available. It would be nice to be able to use this same logic no matter what files are being used for input/output.


This is meant to turn code like the following:

orig_stdin = sys.stdin

orig_stdout = sys.stdout

with open('/dev/tty', 'r+') as f:

    sys.stdin = f

    sys.stdout = f

    name = input('Name? ')

sys.stdin = orig_stdin

sys.stdout = orig_stdout

print(name)


into something more like this:

with open('/dev/tty', 'r+') as f:

    name = input('Name? ', fin=f, fout=f)

print(name)


It's nice that it makes the assignment to a global variable to change the file used for input/output to no longer be needed.


I had this idea the other day, and I realized that it would be super easy to implement, so I went ahead the threw up a PR also.


Would love to see if anyone else is interested in this. I think it's pretty cool that the core logic really didn't need to be changed other than plumbing in the new args.


FWIW, this change introduces no regressions and adds a few more tests to test the new functionality. Honestly, I think this functionality could probably be used to simplify some of the other tests as well, but I wanted to gauge what folks thought of the change before going farther.


Wren Turkal

Existential Production Engineer of the Ages

Facebook, Inc.
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