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DEP: deprecate numpy.typing.NBitBase#28884

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jorenham:typing/deprecate-npt.NBitBase
May 3, 2025
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DEP: deprecate numpy.typing.NBitBase#28884
charris merged 2 commits intonumpy:mainfrom
jorenham:typing/deprecate-npt.NBitBase

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@jorenham jorenham commented May 1, 2025 •
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numpy.typing.NBitBase is intended to be used as e.g.

import numpy as np
import numpy.typing as npt

def f[NT: npt.NBitBase](x: np.complexfloating[NT]) -> np.floating[NT]: ...

This will lead to problems for float64 and complex128, which were changed into concrete subtypes of floating and complexfloating in NumPy 2.2. That means that e.g. floating[_64Bit] is no longer assignable to float64, causing type-checkers to reject x: float64 = f(complex128(1)). This defeats its purpose, and should therefore no longer be used.

The general alternative is to use typing.overload:

import numpy as np
from typing import overload

@overload
def f(x: np.complex64) -> np.float32: ...
@overload
def f(x: np.complex128) -> np.float64: ...
@overload
def f(x: np.clongdouble) -> np.longdouble: ...

And even though it has gotten more verbose, it requires less mental to interpret.

In situations where the input scalar type is the same as the output type, there's a simpler alternative:

Old:

import numpy as np
import numpy.typing as npt

def f[NT: npt.NBitBase](x: np.floating[NT]) -> np.floating[NT]: ...

New:

import numpy as np

def f[FloatT: np.floating](x: FloatT) -> FloatT: ...

This also makes the code more readable, IMO.

Note that at the moment, float32 is assignable to floating[_32Bit], because it is defined as a type alias, as opposed to a proper subtype. In NumType this has already been fixed (i.e. it's incorrect) for all scalar types.

@jorenham jorenham added 07 - Deprecation 56 - Needs Release Note. Needs an entry in doc/release/upcoming_changes 41 - Static typing labels May 1, 2025
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@jorenham jorenham removed the 56 - Needs Release Note. Needs an entry in doc/release/upcoming_changes label May 1, 2025
@jorenham jorenham marked this pull request as ready for review May 1, 2025 18:54
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jorenham commented May 1, 2025

I'm a sphinx noob, so I had Claude write the release note. Content-wise it looks fine to me, but there might be sphinx issues or something 🤷🏻.

@jorenham jorenham force-pushed the typing/deprecate-npt.NBitBase branch from c404985 to 8176a27 Compare May 1, 2025 18:58
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jorenham commented May 1, 2025

Diff from mypy_primer, showing the effect of this PR on type check results on a corpus of open source code:

pandas (https://github.com/pandas-dev/pandas)
+ pandas/_typing.py:91: error: Unused "type: ignore" comment  [unused-ignore]

See pandas-dev/pandas#61387

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@jorenham jorenham force-pushed the typing/deprecate-npt.NBitBase branch from 8176a27 to c2fb472 Compare May 1, 2025 21:18
@jorenham jorenham force-pushed the typing/deprecate-npt.NBitBase branch from c2fb472 to 72fcaa9 Compare May 1, 2025 21:23
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github-actions bot commented May 1, 2025

Diff from mypy_primer, showing the effect of this PR on type check results on a corpus of open source code:

pandas (https://github.com/pandas-dev/pandas)
+ pandas/_typing.py:91: error: Unused "type: ignore" comment  [unused-ignore]

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charris commented May 2, 2025

Do you consider this ready? I note several runs of mypy_primer.

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jorenham commented May 3, 2025

Do you consider this ready? I note several runs of mypy_primer.

Ah yea sorry about that, I was tweaking "vibe coding" the release notes for a bit before. But it should be ready for review.

@charris charris merged commit 297caea into numpy:main May 3, 2025
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charris commented May 3, 2025

Thanks Joren, let's see how it goes.

The vibe coding is an interesting experiment. Is there anyway to control the line length?

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jorenham commented May 3, 2025

Is there anyway to control the line length?

Hmmm, I guess you could try including it in the prompt 🤷🏻?

@jorenham jorenham deleted the typing/deprecate-npt.NBitBase branch May 3, 2025 20:12
@jorenham jorenham mentioned this pull request Jun 9, 2025
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@jorenham jorenham mentioned this pull request Jul 24, 2025
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