Guido van Rossum wrote on 7/6/18 08:31:
Thanks for an interesting discussion. I would also urge people to limit the
use of such sentinels for cases where it is *really* important to
distinguish between, say, f(None) and f(). In most cases using def
f(arg=None) is fine, and often it is even a virtue that passing None or
omitting an argument has exactly the same meaning. (I do know there a cases
where this doesn't apply -- I just think they ought to be fairly unusual.)
One of the most common places I use a non-None sentinel is when None is
a valid value in a dictionary:
_missing = object()
if mydict.get('foo', _missing) is _missing:
# it ain't there
I generally don't feel like a more complicated repr is valuable here, so
I haven't really wanted a built-in sentinel in a long time. My search
fu is weak today, but I'm pretty sure I suggested such a thing (and was
rightly persuaded against it) many years ago.
what-goes-around-comes-around-ly y'rs,
-Barry
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