dv.add_slider creates a slider inside the gui and a float variable named var_name. This variable is connected with the slider and changes with the slider, and can be used throughout the code. Slider ...

Another way to test interface compatibility in Python is to use unittest.mock, which is a module that allows you to create mock objects that mimic the behavior and attributes of real objects.

Ok so technically Python is call-by-object and how it behaves depends on what you're doing. The 1st case below behaves like pass-by-value as expected.