[Python-ideas] breaking out of module execution

[Ethan Furman]

Georg Brandl wrote:
> On 24.04.2012 22:20, M.-A. Lemburg wrote:
> 
>>>> Think of code like this (let's assume the "break" statement is used
>>>> for stopping module execution):
>>>>
>>>> """
>>>> #
>>>> # MyModule
>>>> #
>>>>
>>>> ### Try using the fast variant
>>>>
>>>> try:
>>>>     from MyModule_C_Extension import *
>>>> except ImportError:
>>>>     pass
>>>> else:
>>>>     # Stop execution of the module code object right here
>>>>     break
>>>>
>>>> ### Ah, well, so go ahead with the slow version
>>>>
>>>> import os, sys
>>>> from MyOtherPackage import foo, bar, baz
>>>>
>>>> class MyClass:
>>>>     ...
>>>>
>>>> def MyFunc(a,b,c):
>>>>     ...
>>>>
>>>> def main():
>>>>     ...
>>>>
>>>> if __name__ == '__main__':
>>>>     main()
>>>> """
>>> There's a subtle bug here that shows that the proposed feature has its
>>> awkward points:  you probably want to execute the "if __name__ == '__main__'"
>>> block in the C extension case as well.
>> No, you don't :-) If you would have wanted that to happen, you'd
>> put the "if __name__..." into the else: branch.
> 
> Not sure I understand.  Your example code is flawed because it doesn't execute
> the main() for the C extension case.  Of course you can duplicate the code in
> the else branch, but you didn't do it in the first place, which was the bug.

It's only a bug if you *want* main() to execute in the C extension case 
-- so for M.A.L. it's not a bug (apparently he meant "I" when he wrote 
"you" ;)

~Ethan~