Python: How to write to and read from an existing PseudoTerminal (pty/pts)

Question

I am attempting to programmatically interact with an existing program that provides an interface via a pseudo terminal (/dev/pts/1)

I have a poor understanding of how this works. I can currently interact crudely but successfully with:
echo SomeCommandToSend >> /dev/pts/1

And can equally crudely retrieve results with:
cat /dev/pts/1

Question: How can I cleanly and programmatically interact with this pseudo terminal from Python?

I have looked at these docs but was unable to see how to use that in this case, as I do not want to spawn a new process, just communicate with an existing one.

Answer 1

Following code will once print hello to your terminal (execute tty in your terminal to get /dev/pts/n) and infinitly read from terminal.

import sys                                           

with open("/dev/pts/1", "wb+", buffering=0) as term:
    term.write("hello".encode())
    while True:
        print(term.read(1).decode(), end='')
        sys.stdout.flush()