How can I use GNU readline when the value of sys.stdin has been changed?

[thePhysicist8]

I'm using Python 3.5.2 on Linux.

I'm trying to get my program to take input from a pipe (i.e. find ~/docs | main.py) and later take input from the terminal. After reading this Stack Overflow post (stackoverflow.com/questions/7141331/pipe-input-to-python-program-and-later-get-input-from-user), I tried opening /dev/tty to replace sys.stdin.

import sys
import readline

def tty_input(prompt):
   with open("/dev/tty") as terminal:
       sys.stdin = terminal
       user_input = input(prompt)
   sys.stdin = sys.__stdin__
   return user_input

The problem with this approach is that GNU readline doesn't work when sys.stdin != sys.__stdin__. I can't use the arrow keys to move the cursor or navigate the history like I can normally. I read of a patch for this issue that was proposed here (bugs.python.org/issue512981), but I don't know that anything came of it.

If there is a way to accept input from both a pipe and the terminal without changing the value of sys.stdin, I'm open to suggestions.

Apologies for the URLs, but I can't post clickable links yet.

[Larz60+]

This is just an idea that may or may not have merit.
While sitting here scratching my butt, I thought,
why not create a thread that monitors stdin. Whenever
activity is detected, notify the main thread which could
then kick off an event. (As in interrupt), that redirects stdin.

You may want to watch this:
An Introduction to Python Concurrency - David Beazley

And perhaps scratch you're butt as well!

[Larz60+]

Welcome to the Forum by the way

[Ofnuts]

I wonder why you would need to do that. If you need to feed a few things to your program while entering more data at the terminal there are other ways. If the caller is a bash script you can use expect to feed input to the terminal, for instance.

[Larz60+]

As stated

This is just an idea that may or may not have merit.

I normally think of the more complicated than necessary solution,
then usually see the more obvious (and simple) solution later.

[wavic]

This is typical for the most of the people including me for the most of the time.

[Skaperen]

in a recent project i needed to redirect stdout and stderr.  the way i did it was to use os.open() to open a new POSIX file descriptor then use a couple calls to os.dup2() to change descriptors 1 and 2.  i just made sure i did stdout,flush() ahead of this.  maybe you can do this for stdin (0).  be sure you have empty buffers to avoid mixed data.

stdout.flush()
fd = os.open(ln,os.O_APPEND|os.O_CREAT|os.O_WRONLY)
os.dup2(fd,1) if fd != 1 else None
os.dup2(1,2)

"ln" means "log name".  this is opening log files for several cloud programs.