On Sun., 1 Nov. 2020, 3:01 pm Guido van Rossum, <gu...@python.org> wrote:
> On Sat, Oct 31, 2020 at 21:48 Dan Stromberg <drsali...@gmail.com> wrote: > >> >> On Sat, Oct 31, 2020 at 9:37 PM Guido van Rossum <gu...@python.org> >> wrote: >> >>> >>> I think this over-stresses the notion that users might want to override >>> the comparison operator to be used. We only have two operators that make >>> sense in this context, 'is' and '==', and really, for almost everything you >>> want to do, '==' is the appropriate operator. (There is a small trickle of >>> bugs caused by people inappropriately using e.g. `if x is 1` instead of `if >>> x == 1`, suggesting that if anything, there is too much freedom here.) The >>> big exception is `None`, where you basically always want to use `is`, which >>> is what PEP 634 does. >>> >> > FWIW, there's an additional exception: >> sentinel = object() >> >> if var is sentinel: >> >> I use this idiom from time to time - instead of None. >> > > You can just write ‘case sentinel’, since object’s == operator uses > identity anyway. > No, you can't, as the other operand might decide it wants to compare equal to your sentinel value. Cheers, Nick. -- > --Guido (mobile) >
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