__main__
— 顶层脚本环境
¶
'__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
.