How a script can know if it has been called with the -i command line option?

[Michele Simionato]

The subject says it all, I would like a script to act differently when
called as
$ python script.py and when called as $ python -i script.py. I looked
at the sys module
but I don't see a way to retrieve the command line flags, where should
I look?
TIA,

          Michele Simionato