[Python-ideas] Avoiding nested for try..finally: atexit for functions?

[Nikolaus Rath]

Andrew Bennetts <andrew-CCXH/aKPDeEYtQj7fl1lsA at public.gmane.org> writes:
> On Tue, Oct 18, 2011 at 10:14:56PM -0400, Nikolaus Rath wrote:
> [...]
>> I would much rather have something like this:
>> 
>> def my_fun():
>>     allocate_res1()
>>     atreturn.register(cleanup_res1)
>>     # do stuff
>>     allocate_res2()
>>     atreturn.register(cleanup_res2)
>>     # do stuff
>>     allocate_res3()
>>     atreturn.register(cleanup_res3)
>>     # do stuff
>>     return
>> 
>> Has the idea of implementing such "on return" handlers ever come up?
>> Maybe there is some tricky way to do this with function decorators?
>
> The "with" statement is a good answer.  If for some reason you need to
> be compatible with version of Python so old it doesn't have it, then try
> the bzrlib.cleanup module in bzr.  It implements the sort of API you
> describe above.

Yes, that's sort of what I was thinking about. I think the API is still
more convoluted than necessary, but that's probably because it works
with Python 2.4.

Having thought about this a bit more, I think it should be possible to
use 'with' rather than decorators to implement something like this:

with CleanupManager() as mngr:
     allocate_res1()
     mngr.register(cleanup_res1)
     # do stuff
     allocate_res2()
     mngr.register(cleanup_res2)
     # do stuff
     allocate_res3()
     mngr.register(cleanup_res3)
     # do stuff
    
The mngr object would just run all the registered functions when the
block is exited.

Thoughts?

Best,

   -Nikolaus

-- 
 »Time flies like an arrow, fruit flies like a Banana.«

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