python __name__使用.

在saltstack原码salt-2015.8.8.2/salt/version.py中

if __name__ == '__main__':
    print(__version__)

经常有程序这样写:

def main():
    ......

if __name == "__main__":
    main();

顺便学习了一下__name__


在模块中直接使用,__name__是__main__;
在模块中导入模块,__name__是模块名;
在类中使用,__name__是类名.

Modules…

Predefined (writable) attributes: __name__ is the module’s name;

… Classes…

Special attributes: __name__ is the class name;

29.4.  — Top-level script environment

'__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.

t@localhost python$ cat namemethod.py 
#!/usr/bin/env python3
def tprint():
    print('__name__ is %s' %(__name__))
if __name__ == '__main__':
    tprint()
else:
    print('import:')
    tprint()
t@localhost python$ ./namemethod.py 
__name__ is __main__
t@localhost python$ cat test.py 
#!/usr/bin/env python3
mport namemethod
tprint()

t@localhost python$ ./test.py 
import:
__name__ is namemethod
__name__ is namemethod