Python 3.6.5 Documentation > "__main__" — Top-level script environment
"__main__" — Top-level script environment *****************************************
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"'__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 "-m".
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