break in a module

[Erik Max Francis]

Eric Snow wrote:
> With modules I sometimes have code at the beginning to do some small
> task if a certain condition is met, and otherwise execute the rest of
> the module body.  Here's my main use case:
> 
>   """some module"""
> 
>   import sys
>   import importlib
>   import util  # some utility module somewhere...
> 
>   if __name__ == "__main__":
>       name = util.get_module_name(sys.modules[__name__])
>       module = importlib.import_module(name)
>       sys.modules[__name__] = module
>   else:
>       # do my normal stuff at 1 indentation level
> 
> I would rather have something like this:
> 
>   """some module"""
> 
>   import sys
>   import importlib
>   import util  # some utility module somewhere...
> 
>   if __name__ == "__main__":
>       name = util.get_module_name(sys.modules[__name__])
>       module = importlib.import_module(name)
>       sys.modules[__name__] = module
>       break
> 
>   # do my normal stuff at 0 indentation level
> 
> So, any thoughts?  Thanks.

The answer would depend on exactly what "normal stuff" you expect your 
module to do if it's not being run as a script (which is what your 
`__name__ == '__main__'` check tests for).  A typical module will define 
it's appropriate attributes, functions, classes, and so on at module 
scope.  It will then end with a test to see if it's being run as a 
script, and then do the appropriate thing.  This allows modules to be 
imported separately from being executed as scripts.

Your sample code makes it hard to understand the use case, especially 
since if you want this hypothetical "module break" to stop executing the 
module, then your `__name__ == '__main__'` test basically does nothing 
useful (it fiddles with some modules -- especially since it appears to 
be they very module that is being executed -- and then quits).

At a more general level, the idea of a "module break" doesn't make much 
sense.  Modules are just collections of things; they can include some 
direct code, but typically consist of mostly definitions.  Modules can 
interact with each other, be called recursively, etc., and so at an 
arbitrary point saying, "break out of this module" doesn't have a great 
deal of meaning.

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