Error with removed init parameters about dataclassy HOT 5 CLOSED

Interesting. I have never got round to benchmarking dataclasses versus this library. I was acutely aware that __call__ is very hot and probably far slower than object.__call__ (which I believe is implemented in C). __new__ is the real equivalent of dataclasses' __init__ so it would be interesting to compare this directly.

I haven't looked at how dataclasses passes arguments to __post_init__, but it's likely it does it statically with metaprogramming rather than dynamically like dataclassy's current __call__ implementation. To be honest, the main reason I haven't obsessed too much about that method is that I use post-init processing very rarely, and when there isn't a custom __init__ dataclassy just uses object.__call__. Now that the library is more or less feature-complete (as I see it so far) performance would be something good to focus on. If it would also be useful to you, any benchmarking you do would likely be very helpful in a new issue.

Anyway, good to know that it's fixed and also that it works with 3.9!

from dataclassy.

Thanks, I've fixed this but I'm not yet awake enough to be completely sure of exactly why it was broken before or commit a proper test!

from dataclassy.

Ah, it's because the earlier slice didn't consider the extra *args parameter added in __new__ to allow argument pass-through to __init__.

Not directly related to the bug but now we use a custom __call__ it might be neater to use the keyword-only indicator * instead of *args.

from dataclassy.

OK, I think that's everything 🙂 If you can confirm everything now works as expected I'll release an update to PyPI.

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Awesome, I tested it and it works!

As a side note, it seems like dataclassy's performance is roughly twice that of the builtin dataclasses. On the project that encountered this bug (it creates many instances of a single dataclass) I was profiling, the runtime roughly doubles from 4 sec with dataclasses to 8 sec with dataclassy.

Most of the time spent is on dataclassy/dataclassy/dataclass.py:104(__call__) and <string>:1(__new__), tested on Python 3.9.

No rush of course to improve this performance, I just wanted to provide a reference point in case you find it useful.

from dataclassy.