user interface - How to tell if python script is being run in a terminal or via GUI?

Question

I'm working in Linux and am wondering how to have python tell whether it is being run directly from a terminal or via a GUI (like alt-F2) where output will need to be sent to a window rather than stdout which will appear in a terminal.

In bash, this done by:

if [ -t 0 ] ; then  
    echo "I'm in a terminal"
else
    zenity --info --title "Hello" --text "I'm being run without a terminal"
fi

How can this be accomplished in python? In other words, the equivalent of [ -t 0 ])?

Answer 1

$ echo ciao | python -c 'import sys; print sys.stdin.isatty()'
False

Of course, your GUI-based IDE might choose to "fool" you by opening a pseudo-terminal instead (you can do it yourself to other programs with pexpect, and, what's sauce for the goose...!-), in which case isatty or any other within-Python approach cannot tell the difference. But the same trick would also "fool" your example bash program (in exactly the same way) so I guess you're aware of that. OTOH, this will make it impossible for the program to accept input via a normal Unix "pipe"!

A more reliable approach might therefore be to explicitly tell the program whether it must output to stdout or where else, e.g. with a command-line flag.