Something about Renpy For loop error : expected statement.

 It takes me over hour to debug.
The simple fact is that under label, we cannot use For loop.
One while is valid to be used under label.
To use For loop, must go with python:

Another Finding is about call screen and show screen.
In past, it seems the second one is more appropriate for my case .
With Screen A and button A, to open Screen B.