turkeify.py

#!/usr/bin/env python3

import pty
import termios
import sys
import tty
import os

FROM_STR = b"#"
TO_STR = "🦃".encode("utf-8")

pid, tty_fd = pty.fork()
if pid == pty.CHILD:
    os.execvp(sys.argv[1], sys.argv[1:])

with os.fdopen(tty_fd, "r") as tty_file:
    stdout_fd = sys.stdout.fileno()
    while True:
        try:
            remaining = os.read(tty_fd, 1024)
        except OSError:
            break
        if len(remaining) == 0:
            break
        remaining = remaining.replace(FROM_STR, TO_STR)
        while len(remaining) > 0:
            written_len = os.write(stdout_fd, remaining)
            remaining = remaining[written_len:]