__main__— Top-level script environment
'__main__' is the name of the scope in which top-level code executes.
A module’s __name__ is set equal to
'__main__' when read from
standard input, a script, or from an interactive prompt.
A module can discover whether or not it is running in the main scope by
checking its own
__name__, which allows a common idiom for conditionally
executing code in a module when it is run as a script or with
python -m but not when it is imported:
if __name__ == "__main__": # execute only if run as a script main()
For a package, the same effect can be achieved by including a
__main__.py module, the contents of which will be executed when the
module is run with