On Sun, Jul 26, 2020 at 8:25 PM Guido van Rossum <gu...@python.org> wrote:
> The only reason I can think of why you are so resistant to this would be > due to poor development practices, e.g. adding tests long after the "main" > code has already been deployed, or having a separate team write tests. > and even then, maybe monkey-patch an __eq__ in for your tests? For my part, I have for sure defined __eq__ for no other reason than tests -- but I'm still glad I did. Though perhaps the idea (sorry, not sure who to credit) of providing a utility for object equality in the stdlib, so that in the common case, it would be simple to write a "standard" __eq__ would be nice to have. (note on that -- make sure it handles properties "properly" -- if that's possible) In fact, defining `__hash__` as returning the constant `42` is better, > because it is fine if two objects that *don't* compare equal still have the > same hash value (but not the other way around). > Really? can anyone recommend something to read so I can "get" this -- it's counter intuitive to me. Is __eq__ always checked?!? I recently was faced with dealing with this issue in updating some old code, and I'm still a bit confused about the relationship between __hash__ and __eq__, and main Python docs did not clarify it for me. > Finally, dataclasses get you all this for free, and they are the future. > That is a great point -- I've learned that the really nice thing about dataclasses is that they keep a separate structure of all the attributes that matter, and some metadata about them -- type, etc. This is really useful, and better (or at least more stable) than simply relying on __dict__ and friends. I'm thinking that a "dataclasstools" package that builds on dataclasses, would be really nice -- clearly something to start on PyPi, but as a unified effort, we could get something cleaner than everyone building their own little bit on their own. -CHB -- Christopher Barker, PhD Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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