What is significant about variables at the top level of a module whose names begin with a single underscore?
What does it mean when a module’s __name__ variable is the string "__main__"?
If the user interactively types the name of a module to test, how 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 future, can we also import from the past?