On Fri, Aug 30, 2019 at 5:51 PM Hongyi Zhao <hongyi.z...@gmail.com> wrote: > > On Fri, 30 Aug 2019 01:29:48 +0200, Peter Otten wrote: > > > Perhaps a simple example can help? > > > > $ cat checktty.py import sys > > > > stream = sys.stdout > > > > if stream.isatty(): > > message = "tty" > > else: > > message = "no tty" > > print(message, file=stream) > > > > When you run the script it prints to the terminal: > > > > $ python3 checktty.py tty > > > > But when you redirect to a pipe or into a file: > > > > $ python3 checktty.py | cat no tty > > > > $ python3 checktty.py > tmp.txt $ cat tmp.txt no tty > > > But, see my example: > > $ cat check-isatty.py > import sys > import time > > if sys.stderr.isatty(): > p = 'tty ' + '\r' > else: > p = 'no tty ' + '\n' > > sys.stderr.write(p) > sys.stderr.flush() > time.sleep(1.0) > > > I run both of the following commands: > > $ python check-isatty.py > $ python check-isatty.py | cat > > Both will output `tty'. So still I cannot figure out the issue. >
That's because sys.stderr is never changing in your example here. Try checking whether sys.stdout is a TTY instead. (Also, why the sleep? Seems unnecessary.) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
