How to pass variables from one class to another

[hobbyist]

How to pass values from one class to another when the class you want to get value from is after. What I mean: Suppose I have two classes:

class One:
    .....
    f = ClassTwoValue

class Two:
    ....
    ClassTwoValue = 2

I want the class One to get the value from class Two. I found solutions (from google search, such as this: https://stackoverflow.com/questions/1999...to-another) only for class Two to get the value from class One... which does not work for my situation... Any ideas?