bookhoweverbefore we dive into that topicbe sure to work through this part' set of lab exercises and before thathere is this quiz to review the topics covered here test your knowledgequiz what is significant about variables at the top level of module whose names begin with single underscore what does it mean when module' __name__ variable is the string "__main__" if the user interactively types the name of module to testhow can your code import it how is changing sys path different from setting pythonpath to modify the module search path if the module __future__ allows us to import from the futurecan we also import from the pasttest your knowledgeanswers variables at the top level of module whose names begin with single underscore are not copied out to the importing scope when the from statement form is used they can still be accessed by an import or the normal from statement formthough the __all__ list is similarbut the logical converseits contents are the only names that are copied out on from if module' __name__ variable is the string "__main__"it means that the file is being executed as top-level script instead of being imported from another file in the program that isthe file is being used as programnot library this usage mode variable supports dual-mode code and tests user input usually comes into script as stringto import the referenced module given its string nameyou can build and run an import statement with execor pass the string name in call to the __import__ or importlib import_module changing sys path only affects one running program (process)and is temporary --the change goes away when the program ends pythonpath settings live in the operating system--they are picked up globally by all your programs on machineand changes to these settings endure after programs exit nowe can' import from the past in python we can install (or stubbornly usean older version of the languagebut the latest python is generally the best python (at least within lines--see longevity!test your knowledgeanswers