How to check whether print() prints to terminal or file?

Question

Is there a way in Python 3 to check whether the following command

print('Hello')

prints to the terminal by using

python3 example.py

or prints to the file by using

python3 example.py > log.txt

...? In particular, is there a way to print different things depending on whether I use > log.txt or not?

Does this answer your question? [How do I determine if sys.stdin is redirected from a file vs. piped from another process?](https://stackoverflow.com/questions/13442574/how-do-i-determine-if-sys-stdin-is-redirected-from-a-file-vs-piped-from-another) — Brian61354270, Jun 30 '22 at 14:08
@Brian After testing the accepted answer in your link (and changing the print statements to print functions for python3), the output was the same: in both cases the output said "terminal", whether I used "> log.txt" or not. So it unfortunately didn't work. — ersbygre1, Jun 30 '22 at 14:11
@ersbygre1 Were you checking _stdin_ or _stdout_? The idea is the same for both, but the code in the dupe uses `sys.stdin.fileno()` (i.e. 0). You want `sys.stdout.fileno()` (i.e. 1) — Brian61354270, Jun 30 '22 at 14:12
Potential duplicates: [Determining if stdout for a Python process is redirected](https://stackoverflow.com/q/1512457/11082165), and [How do I detect whether sys.stdout is attached to terminal or not?](https://stackoverflow.com/q/1077113/11082165), and [How to recognize whether a script is running on a tty?](https://stackoverflow.com/q/858623/11082165) — Brian61354270, Jun 30 '22 at 14:17

score 3 · Accepted Answer · answered Jun 30 '22 at 14:11

3

I think you're looking for:

writing_to_tty = sys.stdout.isatty()

So...

if sys.stdout.isatty():
    print("I'm sending this to the screen")
else:
    print("I'm sending this through a pipeline or to a file")

answered Jun 30 '22 at 14:11

Thickycat

This worked exactly like I imagined it. Thanks for the `.isatty()` function! – ersbygre1 Jun 30 '22 at 14:14

1 Answers1