On Feb 10, 2010, at 05:28 PM, Bjorn Tillenius wrote: > think we should be a bit careful using it for other things than files. >I'm sure there are good use cases for using with with custom >implementations, but we should be careful not to over-use it. Just >because it's easy to write, doesn't mean that we should do it. It's very >easy to get carried away, wanting to use new features just because. It's >important to think about the end result.
I completely agree that we should be careful, and tasteful, but of course
that's true of any wacky Python feature, not just with-statements. :)
I sort of envision that we'll find some common patterns in our code that fit
well as context managers. I'm hoping that we can write a few generic classes,
and that we'll get used to seeing them in our code. Things like temporarily
changing the umask or cwd come to mind. Like a lot of these, it'll take some
time to propagate across our collective consciousness, so when the dev and
reviewer agree that a useful context manager has been written, documenting it
in the wiki and/or mailing list would be helpful.
>So, when writing context manager implementations, you (and the reviewer)
>should ask youself the question: how easy is it to see what's going on
>when the with statement is used? The with statement does add a level of
>magic. If you need to chase down the implementation to figure out what's
>going on, it's not a good design. As I see it, the with statement is
>mainly useful wehre you have a well-known behaviour, where it's easy to
>find out what's going on (for example from the name), or when the
>clean-up step isn't important. This doesn't mean that we should avoid
>writing our own context managers at all cost, just that we should
>evaluate the benefit. The more an object is used in the code, the more
>likely it is that the behaviour will be well-known.
Right. Above all, if you do decide to write a context manager, making it read
well in English when used as the target of the 'with' is half the battle.
with cwd('/path/to/stuff'):
# ...
is pretty obvious.
-Barry
signature.asc
Description: PGP signature
_______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : launchpad-dev@lists.launchpad.net Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
