On Feb 02, 2010, at 06:21 PM, Jeroen Vermeulen wrote: >(Irrelevant gripes: it's a thin layer of sugar;
True, but it's a tasty bit of sugar. I find that carefully used,
with-statements are more readable than try/finallys.
>it doesn't scale well for more than resource;
'one'?------------------------------^
It's awkward to do in Python 2.6, but possible:
>>> from contextlib import nested
>>> with nested(open('/etc/passwd'), open('/etc/group')) as (a, b):
... pass
But easier in Python 2.7 and 3:
>>> with open('/etc/passwd') as a, open('/etc/group') as b:
... pass
>The justification for this design was transactions: it lets you write
>transaction classes don't need explicit commits or aborts, because they
>can see for themselves if the code block exits normally or with an
>exception.
I'm not sure the with-statement was designed for transactions, but one good
reason why it shouldn't be used for transactions is because (IME) proper
handling doesn't fit into pure try/finally:
txn = transaction.begin()
try:
modify_the_database()
except:
# Yes, bare except.
txn.abort()
else:
# Ah, everything succeeded.
txn.commit()
That's not a good fit for 'with'. I suppose you can wedge it into the context
manager protocol, but it wouldn't be the first thing I'd reach for.
I guess that means we (mostly) agree! :)
-Barry
signature.asc
Description: PGP signature
_______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
