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Diffstat (limited to 'Doc/library/__main__.rst')
| -rw-r--r-- | Doc/library/__main__.rst | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/Doc/library/__main__.rst b/Doc/library/__main__.rst index a1d3c24..a46993d 100644 --- a/Doc/library/__main__.rst +++ b/Doc/library/__main__.rst @@ -5,13 +5,19 @@ .. 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``. |