[Python-checkins] cpython (3.4): #15104: improve the discussion of __main__.
python-checkins at python.org
Mon Apr 14 21:06:18 CEST 2014
user: R David Murray <rdmurray at bitdance.com>
date: Mon Apr 14 15:04:47 2014 -0400
#15104: improve the discussion of __main__.
Patch by Sam Lucidi.
Doc/library/__main__.rst | 16 +++++++++++-----
1 files changed, 11 insertions(+), 5 deletions(-)
diff --git 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
+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
+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.
Repository URL: http://hg.python.org/cpython
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