Question

I want a program to do one thing if executed like this:

cat something | my_program.py 

and do another thing if run like this

my_program.py 

But if I read from stdin, then it will wait for user input, so I want to see if there is anything to read before trying to read from stdin.

Answer 1

If you want to detect if someone is piping data into your program, or running it interactively you can use isatty to see if stdin is a terminal:

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