Hacker News Reader

>I don't think that's a great example for Python; that's just knowing what "is" is for. The fact that it works the same as == for small integers in CPython is an optimisation showing through, but only in a place where it doesn't really matter.

Python should have prevented checking primitives with is though -- only let object pointers...

View on HN

I believe they're still object pointers in CPython, they're just ordinary singletons; in other implementations, they aren't even singletons. Python's object model doesn't have primitives. Adding special rules around them would significantly complicate the language as well as limit the implementors' ability to fiddle with the ranges of pre-allocated instances, for minimal benefit.

>in other implementations, they aren't even singletons

That would have been less surprising (since for < 256 the singleton-ness means all same valued instances have the same "address" (id), so behave in equality check as if they were plain numbers).

Integers are object pointers, too. CPython just so happens to preallocate a range of small integers[0].

[0]: https://github.com/python/cpython/blob/master/Objects/longob...

Reply on news.ycombinator.com