Moreover, i think that there are more than the "transactional"
use cases mentioned in the PEP. For example, a handler may want to log exceptions to some tracing utility or it may want to swallow certain exceptions when
its block does IO operations that are ok to fail.
With the current PEP 310 definition, these can be manually handled using sys.exc_info() in the __exit__ method. Cleaning up my earlier transaction handler example:
class transaction(object):
def __enter__(self):
begin_transaction() def __exit__(self):
ex = sys.exc_info()
if ex[0] is not None:
abort_transaction()
else:
commit_transaction()Alternately, PEP 310 could be defined as equivalent to:
if hasattr(x, '__enter__'):
x.__enter__()
try:
try:
...
except:
if hasattr(x, '__except__'):
x.__except__(*sys.exc_info())
else:
raise
finally:
x.__exit__()Then the transaction handler would look like:
class transaction(object):
def __enter__(self):
self.aborted = False
begin_transaction() def __except__(self, *exc_info):
self.aborted = True
abort_transaction() def __exit__(self):
if not self.aborted:
commit_transaction()
Cheers, Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://boredomandlaziness.skystorm.net
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