Understanding is being able to read python code with no reference book/manual. Applying is writing python code with no reference book/manual. In both cases do

Understanding is being able to read python code with no reference book/manual. Applying is writing python code with no reference book/manual. In both cases doing it properly means you are reasonably fast while being confident about the correctness (either that you correctly predicted the program's behavior or that you wrote bug-free software).