Should variables in class be defined as constants (POM)

We are having an argument with a colleague.

We are refactoring all our code for Autotests. We partly decideded, that variables will be grouped in classes. Something similar to web Page Object Model.

I have to emphasize that it is not web system we are writing tests for, but windows app. Our variables will vary from input for selection to some "strings" for auto functions in the app. (But I did not find any particular information about object models for such cases, so trying to work it out by the web standards)

So the question is: should the variables in classes be defined as constants?

Bonus: it's python.