What is it

__main__ is the name of the scope in which top-level code executes. A module’sname is set equal to__main__ when read from standard input, a script, or from an interactive prompt.

A module can discover whether 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 withpython -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 amain.py module, the contents of which will be executed when the module is run with -m.

For example, we are developing a script designed to be used as a module, we should do:

>>>defadd(a, b):...return a+b...>>>if __name__=="__main__":...     add(3,5)

Advantages

1. Every Python module has it’s__name__ defined and if this is__main__, it implies that the module is run standalone by the user, and we can do corresponding appropriate actions.
2. If you import this script as a module in another script, thename is set to the name of the script/module.
3. Python files can act as either reusable modules, or as standalone programs.
4. if __name__ == "__main__": is used to execute some code only if the file is run directly, and is not being imported.