On Fri, May 8, 2020 at 11:39 PM Steven D'Aprano <st...@pearwood.info> wrote:
> "More important" according to whose needs? > I dunno. To mine? To "beginner programmers"? To numeric computation? I can weaken my 'note' to 'purport' if that helps. (3) Whereas the proposed duck-typing sequence equality relies on > the ordinary meaning of equality, applied element by element, > ignoring the type of the containers. > I think this one is our main disagreement. I think a meaning for "equality" in which a tuple is equal (equivalent) to a list with the same items inside it is strikingly different from the ordinary meaning of equality. I don't deny that it is sometimes a useful question to ask, but it is a new and different question than the one answered by '==' currently. In my mind, this new kind of equality is MORE DIFFERENT from the current meaning than would be case-folded equivalence of strings, for example. > (1) They require a specialised equivalence relation apart from > `==`. Such as math.isclose(), a case insensitive comparison, > a JSON comparison. > Actually, this could perfectly well live on the types rather than in the modules. I mean, I could do it today by defining .__eq__() on some subclasses of strings, floats, dicts, etc. if I wanted to. But hypothetically (I'm not proposing this), we could also define new operators .__eq2__(), .__eq3__(), etc. that would be called when Python programmers used the operators `===`, `====`, etc. With these new operators in hand, we might give meanings to these new kinds of equivalence: (1, 2, 3) === [1, 2, 3] # has_same_items() "David" === "daviD" # a.upper() == b.upper() "David" ==== "dabit" # soundex(a, b) 3.14159265 === 3.14159266 # math.isclose(a, b) It's competely general in a way that the other equivalences aren't. > Umm... no, it's really not. It's a special kind of equivalence that I guess applies to the Sequence ABC. Or maybe the Collection ABC? But to be really useful, it probably needs to work with things that don't register those ABCs themselves. I would surly expect: (1, 2, 3) === np.array([1, 2, 3]) Also, if this were a thing. But what about dicts, which are now ordered, and hence sequence-like? Or dict.keys() if not the dict itself? I'm sure reasonable answers could be decided for questions like that, but this is FAR from "completely general" or a transparent extension of current equality. -- The dead increasingly dominate and strangle both the living and the not-yet born. Vampiric capital and undead corporate persons abuse the lives and control the thoughts of homo faber. Ideas, once born, become abortifacients against new conceptions.
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