check and set nonblocking option to stdin and stdout

nonblocking.py

import fcntl, sys, os

def get_status(fileno):
    fl = fcntl.fcntl(fileno, fcntl.F_GETFL)
    if (fl & os.O_NONBLOCK) == os.O_NONBLOCK:
        return "nonblocking"
    else:
        return "blocking"

def set_nonblocking(fileno):
    fl = fcntl.fcntl(fileno, fcntl.F_GETFL)
    return fcntl.fcntl(fileno, fcntl.F_SETFL, fl | os.O_NONBLOCK)

def set_blocking(fileno):
    if get_status(fileno) == "nonblocking":
        fl = fcntl.fcntl(fileno, fcntl.F_GETFL)
        return fcntl.fcntl(fileno, fcntl.F_SETFL, fl - os.O_NONBLOCK)
    else:
        return 0


stdin = sys.stdin.fileno()
stdout = sys.stdout.fileno()

print("stdin: %s, stdout: %s" % (get_status(stdin), get_status(stdout)))

print("")
print("making blocking")
set_blocking(stdin)
set_blocking(stdout)

print("stdin: %s, stdout: %s" % (get_status(stdin), get_status(stdout)))

print("")
print("making nonblocking")
set_nonblocking(stdin)
set_nonblocking(stdout)

print("stdin: %s, stdout: %s" % (get_status(stdin), get_status(stdout)))

result-arch-linux

% uname -a
Linux mini-arch 4.11.3-1-ARCH #1 SMP PREEMPT Sun May 28 10:40:17 CEST 2017 x86_64 GNU/Linux

% python3 --version
Python 3.6.1

% python3 nonblocking.py 
stdin: blocking, stdout: blocking

making blocking
stdin: blocking, stdout: blocking

making nonblocking
stdin: nonblocking, stdout: nonblocking

% python2 --version 
Python 2.7.13

% python2 nonblocking.py 
stdin: blocking, stdout: blocking

making blocking
stdin: blocking, stdout: blocking

making nonblocking
stdin: nonblocking, stdout: nonblocking