Control stript which is runing in background.

[Petro]

Hi. 
I would like to make something like this:
A python script would run headlessly in the background.
I would like to control the script from the command line using other python scripts or from the python shell.
>From time to time I would ask the main script to create a popup window with an image or a plot.
What would be the proper way to approach it. How to make communication between two scripts?
Thank you.
Petro.