On 3 Feb. 2018 1:09 am, "Eric V. Smith" <e...@trueblade.com> wrote:
The problem with dropping hash=True is: how would you write __hash__ yourself? It seems like a bug magnet if you're adding fields to the class and forget to update __hash__, especially in the presence of per-field hash=False and eq=False settings. And you'd need to make sure it matches the generated __eq__ (if 2 objects are equal, they need to have the same hash value). I think anyone that does this needs to think *very* carefully about how they do it, and offering both "hash=True" and "frozen=True" is an attractive nuisance that means people will write "hash=True" when what they wanted was "frozen=True". In particular, having to work out how write a maintainable "__hash__" will encourage folks to separate out the hashed fields as a separate frozen subrecord or base class. If this proves to be an intolerable burden then the short hand spelling could be added back in 3.8, but once we ship it we're going to be stuck with explaining the interactions indefinitely. Cheers, Nick.
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