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register cleanup handler

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  register cleanup handler Neal Becker <ndbecker2@gmail.com> - 2015-07-24 10:57 -0400
    Re: register cleanup handler Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2015-07-24 18:41 +0200
      Re: register cleanup handler Neal Becker <ndbecker2@gmail.com> - 2015-07-24 13:35 -0400

#94507 — register cleanup handler

I have code like:

if (condition):
  do_something_needing_cleanup

code_executed_unconditionally

<cleanup has to happen here if required, even if above did return, continue 
or exception>

Now, how can I make sure cleanup happens?  Actually, what I really would 
like, is:

if (condition):
  do_something_needing_cleanup
  register_scoped_cleanup (cleanup_fnc)

code_executed_unconditionally


So, any thoughts/hopes of python being able to do something like this?

I know we have try/finally, but I don't think that helps here, because
code_executed_unconditionally couldn't be inside the try.  Or am I missing 
something obvious?

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#94512

On 24-7-2015 16:57, Neal Becker wrote:
> I have code like:
> 
> if (condition):
>   do_something_needing_cleanup
> 
> code_executed_unconditionally
> 
> <cleanup has to happen here if required, even if above did return, continue 
> or exception>
> 
> Now, how can I make sure cleanup happens?  Actually, what I really would 
> like, is:
> 
> if (condition):
>   do_something_needing_cleanup
>   register_scoped_cleanup (cleanup_fnc)
> 
> code_executed_unconditionally
> 
> 
> So, any thoughts/hopes of python being able to do something like this?
> 
> I know we have try/finally, but I don't think that helps here, because
> code_executed_unconditionally couldn't be inside the try.  Or am I missing 
> something obvious?
> 

Sounds like you want a context manager, see
https://docs.python.org/3/library/contextlib.html#replacing-any-use-of-try-finally-and-flag-variables

Irmen

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#94514

Irmen de Jong wrote:

> On 24-7-2015 16:57, Neal Becker wrote:
>> I have code like:
>> 
>> if (condition):
>>   do_something_needing_cleanup
>> 
>> code_executed_unconditionally
>> 
>> <cleanup has to happen here if required, even if above did return,
>> continue or exception>
>> 
>> Now, how can I make sure cleanup happens?  Actually, what I really would
>> like, is:
>> 
>> if (condition):
>>   do_something_needing_cleanup
>>   register_scoped_cleanup (cleanup_fnc)
>> 
>> code_executed_unconditionally
>> 
>> 
>> So, any thoughts/hopes of python being able to do something like this?
>> 
>> I know we have try/finally, but I don't think that helps here, because
>> code_executed_unconditionally couldn't be inside the try.  Or am I
>> missing something obvious?
>> 
> 
> Sounds like you want a context manager, see
> https://docs.python.org/3/library/contextlib.html#replacing-any-use-of-try-finally-and-flag-variables
> 
> Irmen

Yes, that looks great!  I'm using py2.7.10, so I tried 'contexter' package.
if (condition):

with ExitStack() as stack:
  if condition:
    do_something()
    def cleanup_resources():
      some_cleanup_using_closure()
    stack.callback(cleanup_resources)
  unconditionally_executed_code_no_worrying_about_cleanup()

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