Unbuffered, non-blocking stdin in Python

input.py

import fcntl
import termios
import sys
import os
import time


class NonBlockingInput(object):

    def __enter__(self):
        # canonical mode, no echo
        self.old = termios.tcgetattr(sys.stdin)
        new = termios.tcgetattr(sys.stdin)
        new[3] = new[3] & ~(termios.ICANON | termios.ECHO)
        termios.tcsetattr(sys.stdin, termios.TCSADRAIN, new)

        # set for non-blocking io
        self.orig_fl = fcntl.fcntl(sys.stdin, fcntl.F_GETFL)
        fcntl.fcntl(sys.stdin, fcntl.F_SETFL, self.orig_fl | os.O_NONBLOCK)

    def __exit__(self, *args):
        # restore terminal to previous state
        termios.tcsetattr(sys.stdin, termios.TCSADRAIN, self.old)
        fcntl.fcntl(sys.stdin, fcntl.F_SETFL, self.orig_fl)


with NonBlockingInput():
    while True:
        c = sys.stdin.read(1)
        print('tick', repr(c))
        time.sleep(0.1)

After use this in case of print() large text I receive:

BlockingIOError: [Errno 35] write could not complete without blocking

It looks fixed if edit def __exit__ like this, to restore blocking output:

    def __exit__(self, *args):
        # restore terminal to previous state
        termios.tcsetattr(sys.stdin, termios.TCSADRAIN, self.old)
        # set for blocking io
        orig_fl = fcntl.fcntl(sys.stdin, fcntl.F_GETFL)
        fcntl.fcntl(sys.stdin, fcntl.F_SETFL, orig_fl | ~ os.O_NONBLOCK)

    fcntl.fcntl(sys.stdin, fcntl.F_SETFL, orig_fl | ~ os.O_NONBLOCK)

This should be & not | but yes, looks good.

Another way is to just remember the orig_fl from __enter__ and restore it directly. Untested but shouldn't harm anything. :)

Thank you! I've edit like this, works fine: https://gist.github.com/lomalkin/9aa8f0c426655a252180b13bbe8e82c2#file-input-py