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.. module:: __main__
:synopsis: The environment where the top-level script is run.
+'__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.
-This module represents the (otherwise anonymous) scope in which the
-interpreter's main program executes --- commands read either from standard
-input, from a script file, or from an interactive prompt. It is this
-environment in which the idiomatic "conditional script" stanza causes a script
-to run::
+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.