BUG: NEP 50 promotion for python scalars is not followed for <ufunc>.outer and <ufunc>.at

Describe the issue:

NEP-50 nicely promotes, e.g., python floats to whatever float dtype an array has. However, for outer functions, this is not followed.

Reproduce the code example:

import numpy as np
a = np.arange(10.0, dtype="f4").reshape(5, 2)
np.add(1.0, a).dtype
# dtype('float32')
np.add.outer(1.0, a).dtype
# dtype('float64')

Error message:

Python and NumPy Versions:

2.4.6
3.14.6 (main, Jun 10 2026, 18:54:31) [GCC 15.2.0]

Runtime Environment:

Not relevant.

How does this issue affect you or how did you find it:

Found while reviewing #32040.

This still seems to be the case with 2.5.1

@mhvk

@mhvk hmm, maybe there are issues in ufunc.at as well?

>>> arr = np.array([2**63], dtype=np.uint64)
>>> np.add(arr, 1)[0]
np.uint64(9223372036854775809)
>>> # correct
>>> np.add.at(arr, 0, 1)
>>> arr[0]
np.uint64(9223372036854775808)
>>> # +1 silently lost

>>> arr = np.zeros(1, dtype=np.uint8)
>>> np.add(arr, -1)
OverflowError: Python integer -1 out of bounds for uint8
>>> np.add.at(arr, 0, -1)
>>> arr[0]
np.uint8(255)

@seberg

Oops... It looks like the initial work missed these other cases where the ufunc has to deal with multiple inputs (.reduce, .reduceat, and .accumulate thankfully cannot suffer from this...). Ping also @seberg...

I opened #32094

Hmmm yeah, I wonder if these even ever supported the value-based paths, but maybe not even and I just forgot the follow-up for these after much time had passed...

Anyway, the past is the past, and I guess it is nice to fix it and aligning things...

(In theory, I always had the half wish that we deferred the construction of the final array until after the promotion is finished, but in practice that diff was too large to push for it at the time.)

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BUG: NEP 50 promotion for python scalars is not followed for <ufunc>.outer and <ufunc>.at #32076

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Reproduce the code example:

Error message:

Python and NumPy Versions:

Runtime Environment:

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BUG: NEP 50 promotion for python scalars is not followed for <ufunc>.outer and <ufunc>.at #32076

Description

Describe the issue:

Reproduce the code example:

Error message:

Python and NumPy Versions:

Runtime Environment:

How does this issue affect you or how did you find it:

Activity

jorenham commented on Jul 23, 2026

ngoldbaum commented on Jul 24, 2026

mhvk commented on Jul 24, 2026

ngoldbaum commented on Jul 24, 2026

seberg commented on Jul 24, 2026

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