How to determine if Python script was run via command line?

Background

I would like my Python script to pause before exiting using something similar to:

raw_input("Press enter to close.")

but only if it is NOT run via command line. Command line programs shouldn't behave this way.

Question

Is there a way to determine if my Python script was invoked from the command line:

$ python myscript.py

verses double-clicking myscript.py to open it with the default interpreter in the OS?

I don't think there's any reliable way to detect this (especially in a cross-platform manner). For example on OS X, when you double-click a .py file and it tuns with "Python Launcher", it runs in a terminal, identically to if you execute it manually.

Although it may have other issues, you could package the script up with something like py2exe or Platypus, then you can have the double-clickable icon run a specific bit of code to differentiate (import mycode; mycode.main(gui = True) for example)