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__pow__(float, float) should be float | complex, not Any #12895

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vbraun opened this issue Oct 24, 2024 · 4 comments
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__pow__(float, float) should be float | complex, not Any #12895

vbraun opened this issue Oct 24, 2024 · 4 comments

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@vbraun
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vbraun commented Oct 24, 2024 •
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Exponentiating a float with fractional power can be float or a complex, but nothing else:

In [1]: 1.0 ** 0.5
Out[1]: 1.0

In [2]: (-1.0) ** 0.5
Out[2]: (6.123233995736766e-17+1j)

But the result is currently typed as Any, but float | complex would be stricter and more self-explanatory

I don't see any technical reason for not doing so, maybe I'm missing something? But getting Any and then have mypy --strict complain about it is definitely a headscratcher.

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@AlexWaygood
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We've tried this before, and it causes too many false positive errors unfortunately. Most people most of the time are only using ** between two positive floats, so it's very confusing for those users to find that mypy infers the result as float | complex when they know it's a float at runtime. You can see some discussion in #7682.

@srittau srittau closed this as not planned Won't fix, can't repro, duplicate, stale Oct 24, 2024
@Akuli
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Akuli commented Oct 24, 2024

Perhaps we could use float | Any.

@hauntsaninja
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See #7682 (comment) , int | Any could be worth a shot

@embray
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embray commented Oct 29, 2024

Most people most of the time are only using ** between two positive floats, so it's very confusing for those users

I don't think we should be doing something wrong just because some users didn't learn basic maths

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@srittau @embray @vbraun @hauntsaninja @Akuli @AlexWaygood