At 10:00 AM 5/11/2005 -0700, Guido van Rossum wrote:
>(3) Full exception information, with the understanding that when
>__exit__() returns normally, exception processing will resume as usual
>(i.e. __exit__() is called from a finally clause). Exceptions raised
>from __exit__() are considered errors/bugs in __exit__() and should be
>avoided by robust __exit__() methods.
FYI, there are still use cases for clearing the exception state in an
__exit__ method, that might justify allowing a true return from __exit__ to
suppress the error. e.g.:
class Attempt(object):
def __init__(self,type,last=False):
self.type = type
self.last = last
def __enter__(self): pass
def __exit__(self,*exc):
if exc and not last and issubclass(exc[0],self.type):
# suppress exception
return True
def retry(count, type=Exception):
attempt = Attempt(type)
for i in range(count-1):
yield attempt
yield Attempt(type, True)
# usage:
for attempt in retry(3):
do attempt:
somethingThatCouldFail()
and:
class logging_exceptions(object):
def __init__(self,logger): self.logger = logger
def __enter__(self): pass
def __exit__(self,*exc):
if exc:
# log and suppress error
self.logger.error("Unexpected error", exc_info=exc)
return True
while True:
do logging_exceptions(my_logger):
processEvents()
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