Ideal way to separate GUI and logic?

[fronagzen at gmail.com]

Well, I'm a newcome to Python, but I'm developing a program with a GUI in tkinter, and I'm wondering what is the best, 'most pythonic' way of doing this?

I could, obviously, write a monolithic block of code.

I can define the logic and the GUI as two separate classes and then call from those classes within a single script.

Those are probably less than ideal.

But how then do I separate out the logic and the GUI? Because the GUI needs to have commands defined for button presses and so forth, and those have to come from the logic section. Do I write the logic in a separate file and then import those to the GUI, and then run it there? Wouldn't it be better to have one file for the GUI, one for the logic, and then a third one that imports from both and then executes the app? How do I do that? (Examples would be nice, if possible.)