I am trying to determine if the following mypy warning is telling me something important.

import numpy as np
from numpy import typing as npt

def test(a: npt.ArrayLike) -> npt.NDArray:

    a = np.asarray(a)
    a = np.abs(a)

    return a

This results in the following warning on the return a line.

Incompatible return value type (got “_SupportsArray[dtype[Any]] | _NestedSequence[_SupportsArray[dtype[Any]]] | bool | int | float | complex | str | bytes | _NestedSequence[bool | int | float | complex | str | bytes]”, expected “ndarray[Any, dtype[Any]]”)Mypyreturn-value

Both the following work without warnings:

return np.abs(a)

b = np.abs(a)
return b

So I can’t tell if there really is an issue with reassigning a to itself in np.abs or if this is one of the many subtleties of numpy typing that I should just work around. The warning remains with many other numpy functions (np.sin,np.ceil, etc.).