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Groups > comp.lang.python > #19659

RE: contextlib.contextmanager and try/finally

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Prasad, Ramit wrote:

>>Like Neil mentioned, a contextmanager generator is wrapped with an
>>__exit__ method that is guaranteed to be called and that explicitly
>>resumes or closes the generator.  So as long as your contextmanager
>>generator is properly written (i.e. it yields exactly once), the
>>finally block will execute in a timely fashion.
> 
> Is that true even in the face of something like sys.exit()?
> What happens if 1) sys.exit is called while in the same thread
> 2) sys.exit is called from another thread but while this thread
> is in context manager?

sys.exit() uses the normal exception mechanism to terminate a program:

>>> import sys
>>> try:
...     sys.exit()
... except SystemExit:
...     print "I'd rather not"
...
I'd rather not
>>>

It won't derail a context manager:

>>> from contextlib import contextmanager
>>> @contextmanager
... def f():
...     try:
...             yield
...     finally: print "bye"
...
>>> import sys
>>> with f():
...     sys.exit()
...
bye
$

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contextlib.contextmanager and try/finally johannh@gmail.com - 2012-01-11 07:45 -0800
  Re: contextlib.contextmanager and try/finally Neil Cerutti <neilc@norwich.edu> - 2012-01-11 16:46 +0000
  Re: contextlib.contextmanager and try/finally Robert Kern <robert.kern@gmail.com> - 2012-01-11 17:14 +0000
  Re: contextlib.contextmanager and try/finally Ian Kelly <ian.g.kelly@gmail.com> - 2012-01-11 10:20 -0700
    Re: contextlib.contextmanager and try/finally johannh@gmail.com - 2012-01-11 09:30 -0800
    Re: contextlib.contextmanager and try/finally johannh@gmail.com - 2012-01-11 09:30 -0800
  RE: contextlib.contextmanager and try/finally "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-01-31 21:07 +0000
  RE: contextlib.contextmanager and try/finally Peter Otten <__peter__@web.de> - 2012-01-31 23:02 +0100
  Re: contextlib.contextmanager and try/finally Ian Kelly <ian.g.kelly@gmail.com> - 2012-01-31 15:09 -0700
    Re: contextlib.contextmanager and try/finally Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-01 02:15 +0000

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