[Python-ideas] Replacing the if __name__ == "__main__" idiom (was Re: making a module callable)

[Terry Reedy]

On 11/24/2013 2:10 PM, Guido van Rossum wrote:
> Haven't followed all of this, but perhaps the simplest thing would be to
> define a new builtin function that returns True in the namespace of the
> main module and false everywhere else. It could be implemented by
> pulling '__name__' out of the caller's local namespace and comparing it
> to '__main__'. We could name this function __main__(), or perhaps less
> dramatic, is_main(). Then you could write
>
> if is_main():
>      <do your main code>

Writing 'is_main' (or anything else) instead of '__name__=='__main__' 
seems silly if it would be the only thing breaking back compatibility.

> For people who want to use this idiom on older platforms too they can
> easily implement it themselves using sys._getframe.

...if one know about sys._getframe and how to use it. The leading 
underscore implies that it is subject to change in each version.

Writing an import (from somewhere dependable) for such a function will 
be as many keystrokes as writing the idiom. For my main project, I have 
a template file that includes 'if __name__.. <run test>' along with 
other project boilerplate.

-- 
Terry Jan Reedy