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I want to get user input from a subprocess in an new terminal.

    import subprocess
    additionalBuildArguments = "defaultarg1"
    proc = subprocess.Popen(["python", "user_input.py", additionalBuildArguments],
                            creationflags=subprocess.CREATE_NEW_CONSOLE,
                            stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    try:
        outs, errs = proc.communicate(timeout=15)
    except subprocess.TimeoutExpired:
        proc.kill()
        outs, errs = proc.communicate()
    additionalBuildArguments = outs or additionalBuildArguments

user_input.py:

import sys

arg = sys.argv[1]
user_input = input(f"Additional build arguments [{arg}] (Push <ENTER> to use these settings):\n")
print(user_input)

as long as I don't set the stdout=subprocess.PIPE and/or the stderr=subprocess.PIPE options I can enter input. But with these options I can't write any input to the console. Indeed I need these options to redirect the stdout, to have access to the printed user_input in the parent process. Does anyone know what's the problem here?

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  • It's really unclear what you are trying to ask. Is there a reason you are running python as a subprocess of itself in the first place? The preferred solution is usually to import the function(s) you want to use from the other file, and run them directly. Commented Oct 4, 2021 at 10:31
  • The python code I am running is a gdb extention script. I use gdb inside of eclipse and the stdin and stdout of gdb somehow isn't redirected to the eclipse console. So I have two options for a workaround to get user input here. The first one is to use some kind of input dialog but I don't found any platform independent solution without using external packages, which I don't want to. So I'm trying to spawn a new termial, which I can interact with and get the user input from there. But this is not working so far. Commented Oct 4, 2021 at 10:38
  • There are many undeclared variables here. Can you try to reduce to a minimal reproducible example which is actually runnable and demonstrates your problem? Commented Oct 4, 2021 at 10:39
  • I changed the code a little bit. Now all variables should be declared. Basiacally I want to spawn a subprocess and get user input using the input() function after that I want to print the user input to stdout which I redircted to the parent process and therefore can read it in the parent process using outs, errs = proc.communicate(timeout=15) Commented Oct 4, 2021 at 10:45

1 Answer 1

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Please note that I do not understand why you want to do this, and feel instinctively that you should not. However, it's perfectly possible: just catpure only stdout:

import sys
from subprocess import run
print("Type away: ", end="")
sys.stdout.flush()
r = run(["python", "-c", "print(input())"], capture_output=True, encoding="utf8")
print(f"You entered {r.stdout}")

EDIT Apparently you are using windows. Per the docs your flag is set when shell=True. With shell=True this works for me, but I have no idea whether it will for you:

import sys
from subprocess import run
print("Type away: ", end="")
sys.stdout.flush()
r = run("python -c 'print(input())'", capture_output=True, shell=True, encoding="utf8")
print(f"You entered {r.stdout}")

This can be chained to run in yet a third process, which would be needed to print whilst also capturing stdout, from a subprocess. But at this point we are in the realm of very horrible hacks.

A better, but still hacky, solution, is to re-phrase the problem a bit. You want to spawn a terminal, which apparently you can do, and the user can interact with it correctly, and then you want to get output from that terminal in the spawning code. STDOUT is not the proper channel for this communication. Personally I would structure my code like this:

in spawning code:

  • generate parametrised script to run in spawned terminal and save it as a temp file
  • spawn subterminal running the generated script
  • wait for completion
  • read temp out file and get data
  • delete both temp script and temp out file

in generated code:

  • do as much as possible (you have a full python, after all)
  • dump output as json to a temporary file

This is still hacky, but it only involves spawning one terminal. Note that I still don't understand why you want to do this, but this should at least work.

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4 Comments

the problem is that I have to spawn a new terminal with the creationflags=subprocess.CREATE_NEW_CONSOLE option, because I can't access the console of the parent process. That's the reason I want to use a subprocess to get the user input. If I try ** r = subprocess.run(["python", "-c", "print(input())"], creationflags=subprocess.CREATE_NEW_CONSOLE, capture_output=True, encoding="utf8"))** it is not working.
this message print("Type away: ", end="") should also be printed in a new spawned terminal because printing to the console in the parent process also does not work. I basically want to emulate an input dialog using a new terminal which is closing after the user entered his input. I want to do that because I cannot use a external lib like Tkinter.
see updated answer
Thank you I will try that! I tried to expain a little bit why I want to do that in a comment under the first answer. I know that this is not clean code but I don't exactely understand why I have the problems with stdin and stdout in my python gdb extension when I run it in eclipse, so I'm trying to find a workaround

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