Module question

[Tuvas]

I know this is probably a very simple question, but I am building a
program that is now at about 2400 lines of code in the main module. I
need to break it up, however, there are certain variables that I would
like to use among all of them, namely the TKinter background. It's
build using tkinter, so, to do anything useful requires having the
master=Tk() variable portable in every interface. I can't just pass
this variable, the real way to do it is to have a global variable. How
can I do this? Thanks!