"Invalid self argument" for numpy's iadd

To Reproduce

from typing import Any

import numpy as np
import numpy.typing as npt

def plus1(array: npt.NDArray[np.integer[Any]]) -> None:
    array += 1

Expected Behavior

No error

Actual Behavior

error: Invalid self argument "ndarray[tuple[int, ...], dtype[integer[Any]]]" to attribute function "iadd" with type "Callable[[ndarray[tuple[int, ...], dtype[numpy.bool[builtins.bool]]], _SupportsArray[dtype[numpy.bool[builtins.bool]]] | _NestedSequence[_SupportsArray[dtype[numpy.bool[builtins.bool]]]] | builtins.bool | _NestedSequence[builtins.bool]], ndarray[_ShapeT_co, _DType_co]]" [misc]

Your Environment

Mypy version used: 1.16.0
Mypy command-line flags: none
Mypy configuration options from mypy.ini (and other config files): none
Python version used: 3.13.2
Numpy version used: 2.2.6

@bersbersbers

@bersbersbers
Is it wrong to use union as follows?

import numpy as np
import numpy.typing as npt

from typing import Any


def plus1(array: npt.NDArray[np.uint8 | np.int8]) -> npt.NDArray[np.uint8 | np.int8]:
    return array + 1

It wouldn't be wrong necessarily, if I enumerated all possible integer types. Question is, why should I need to do that, considering that np.integer exists? :)

I also tried this, with varying success:

from typing import Any

import numpy as np
import numpy.typing as npt

# works
def plus1a(array: npt.NDArray[np.signedinteger[Any]]) -> None:
    array += 1


# works
def plus1b(array: npt.NDArray[np.unsignedinteger[Any]]) -> None:
    array += 1


# fails
def plus1c(array: npt.NDArray[np.signedinteger[Any] | np.unsignedinteger[Any]]) -> None:
    array += 1


# fails
def plus1d(array: npt.NDArray[np.integer[Any]]) -> None:
    array += 1

It's defined as follows in the numpy stubs:

@overload
def __iadd__(self: NDArray[np.bool], other: _ArrayLikeBool_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(
    self: NDArray[unsignedinteger[Any]],
    other: _ArrayLikeUInt_co | _IntLike_co,
    /,
) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[signedinteger[Any]], other: _ArrayLikeInt_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[float64], other: _ArrayLikeFloat_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[floating[Any]], other: _ArrayLikeFloat_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[complex128], other: _ArrayLikeComplex_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[complexfloating[Any]], other: _ArrayLikeComplex_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[timedelta64], other: _ArrayLikeTD64_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[datetime64], other: _ArrayLikeTD64_co, /) -> ndarray[_ShapeT_co, _DType_co]: ...
@overload
def __iadd__(self: NDArray[object_], other: Any, /) -> ndarray[_ShapeT_co, _DType_co]: ...

https://github.com/numpy/numpy/blob/2b686f659642080e2fc708719385de6e8be0955f/numpy/__init__.pyi#L3334-L3357

So since there is no self: integer, self: number, or self: generic, mypy rejects this call to __iadd__. Mypy 1.15.0 and 1.16.0 behave in the same way, so this is not a mypy regression or something.

It's worth noting that pyright does not reject this. I'm guessing that it falls back to __add__ if the overloads of __iadd__ are exhausted.

But even so, I agree that your example should be accepted by all type-checkers. I'll try to get this fixed before the upcoming numpy 2.3 release, but it might not make it in time (2.3 is about to be released).

edit: see numpy/numpy#29092

@jorenham

@jorenham thanks for taking care of this. Just one bit:

Mypy 1.15.0 and 1.16.0 behave in the same way

I disagree at least partially - at least in my code base, this issue started appearing after 1.16.0 was released, and going back to 1.15.0 fixes it. Maybe my MWE above also triggers something in 1.15, but something definitely changed with 1.16.

I'll try to get this fixed before the upcoming numpy 2.3 release, but it might not make it in time (2.3 is about to be released).

This will be fixed in the upcoming numpy 2.3.0 release.

Is this fixed now? I run into a similar problem with numpy version 2.3.3. The only difference is that I use np.floating and np.number, which mypy still seems to complain about for __iadd__ and __isub__. The linked PR does not seem to address these cases.

Is this fixed now? I run into a similar problem with numpy version 2.3.3. The only difference is that I use np.floating and np.number, which mypy still seems to complain about for __iadd__ and __isub__. The linked PR does not seem to address these cases.

Ah I didn't realize that this was also affecting number and floating, since that wasn't mentioned in the OP. I'll try to get those ones fixed as well then.

I guess the whole numpy type hierarchy is in principle affected. It would be great if there was a more systematic way to include these type hints (instead of spelling out each alternative individually).

It would be great if there was a more systematic way to include these type hints (instead of spelling out each alternative individually).

There is :) I've implemented it in https://github.com/numpy/numtype (not in numpy itself because that'd be backwards incompatible)

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"Invalid self argument" for numpy's iadd #19171

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iwakitakuma33 commented on May 30, 2025

bersbersbers commented on May 30, 2025

jorenham commented on May 30, 2025

bersbersbers commented on May 30, 2025

jorenham commented on Jun 2, 2025

david-zwicker commented on Sep 30, 2025

jorenham commented on Sep 30, 2025

david-zwicker commented on Sep 30, 2025

jorenham commented on Sep 30, 2025

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"Invalid self argument" for numpy's `iadd` #19171