python print() crash script when it's detached from console & console closed

Question

I have a python3 script which I run from console. When I try to run it detached from console using

1. script.py & disown -f
2. setsid -f script.py

then I close the console, the script crash after a while.

If I detach it using:

3. nohup script.py &
4. at now
   script.py
   Ctrl+D

it keeps running.

Script sleep, wake up every 10s do Some processing, print some output. I discovered the script is crashing because of print(). When I comment out the lines with print(), it run without problems when I detached it from console and console is closed.

I solved this by using logging module:
logging.basicConfig(format='%(message)s', encoding='utf-8', level=logging.INFO,handlers=[logging.StreamHandler(sys.stdout)])
and replace print() with logging.info()

So, stdout is "closed"/"invalid" when the script is detached from console using first 3 methods then console is closed. I knew that but I did not know will affect python, bash script don't care about it. 4th method does not close stdout, the output is sent on mail, so that's why it works.

I am curious how can I check in this situation if it is safe to write to stdout, using print() or sys.stdout.write() ?

I tried both of these conditions

if sys.stdout.closed==False 
if sys.stdout is not None

but print() is still called when the script is detached from console using above first 2 methods, then console is closed.

#!/usr/bin/python3
import time
import sys

for i in range(1,100):
    # same result
    #if sys.stdout.closed==False
    if sys.stdout  is not None 
        print(str(i))
    time.sleep(10)

Answer 1

sys.stdout.writable return true when script.py is detached from terminal using 1. and 2. and calling print() crash the script.

But I found that I can check if script is still connected to tty with:

if sys.stdout.isatty() :
    print(...)

this works to avoid print() when script is detached from tty.