On Thu, 2004-03-18 at 13:39, Andrew Koenig wrote:
> > A very common use case in Python is where None is a valid value in a
> > dictionary:
> >
> > missing = object()
> >
> > if d.get('somekey', missing) is missing:
> > # it ain't there
> >
> > It even reads well!
>
> Indeed. Of course, object() is mutable, so there is no proposal to change
> the meaning of this program. What I'm concerned about is someone trying to
> do the same thing this way:
>
> missing = 'missing'
>
> if d.get('somekey', missing) is 'missing':
> # it ain't there
>
> This code contains a bug, but on an implementation that interns strings that
> happen to look like identifiers, no test will detect the bug.
Sure, but it's long been recommended against doing stuff like:
try:
foo()
except 'quit':
pass
def foo():
raise 'quit'
This doesn't seem like it's something broken that needs fixing. Once
you understand what's going on, it makes sense.
-Barry
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