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.