type hint array functions

[raybellwaves]

Does any have any recommendation of type hinting generic array functions? https://numpy.org/devdocs/reference/typing.html#numpy.typing.ArrayLike looks interesting.

Say I have a function:

def double(a):
    return a + a

which I want to apply to an xarray object (xr.DataArray or xr.Dataset) (my main type). However, for testing and other purposes I may want to use it on a numpy.ndarray or dask.array.

With numpy typing I can write
file.py:

import numpy.typing as npt

def double(a: npt.ArrayLike) -> npt.ArrayLike:
    return a + a

but when I run mypy file.py I get long error message (see below) of Unsupported ...

np.version : 1.21.4
mypy.version : 0.910

mypy --install-types --non-interactive file.py will get rid of the first three lines in the Traceback below.

I apologize this isn't a strict xarray questions but curious how people type hint generic array functions.

❯ mypy test.py
miniconda3/envs/test_env/lib/python3.9/site-packages/numpy/_pytesttester.py:128: error: Cannot find implementation or library stub for module named "pytest"
miniconda3/envs/test_env/lib/python3.9/site-packages/numpy/_pytesttester.py:128: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
test.py:4: note: (Skipping most remaining errors due to unresolved imports or missing stubs; fix these first)
test.py:4: error: Unsupported left operand type for + ("Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]" and "int")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]" and "float")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]" and "complex")
test.py:4: error: Unsupported left operand type for + ("_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("_SupportsArray[dtype[Any]]" and "bool")
test.py:4: error: Unsupported operand types for + ("_SupportsArray[dtype[Any]]" and "int")
test.py:4: error: Unsupported operand types for + ("_SupportsArray[dtype[Any]]" and "float")
test.py:4: error: Unsupported operand types for + ("_SupportsArray[dtype[Any]]" and "complex")
test.py:4: error: Unsupported left operand type for + ("Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("Sequence[_SupportsArray[dtype[Any]]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[_SupportsArray[dtype[Any]]]" and "int")
test.py:4: error: Unsupported operand types for + ("Sequence[_SupportsArray[dtype[Any]]]" and "float")
test.py:4: error: Unsupported operand types for + ("Sequence[_SupportsArray[dtype[Any]]]" and "complex")
test.py:4: error: Unsupported left operand type for + ("Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[_SupportsArray[dtype[Any]]]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[_SupportsArray[dtype[Any]]]]" and "int")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[_SupportsArray[dtype[Any]]]]" and "float")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[_SupportsArray[dtype[Any]]]]" and "complex")
test.py:4: error: Unsupported left operand type for + ("Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]" and "int")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]" and "float")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]" and "complex")
test.py:4: error: Unsupported left operand type for + ("Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]" and "int")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]" and "float")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]" and "complex")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "str")
test.py:4: error: Unsupported operand types for + ("bool" and "bytes")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]")
test.py:4: error: Unsupported operand types for + ("bool" and "Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("int" and "_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("int" and "str")
test.py:4: error: Unsupported operand types for + ("int" and "bytes")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]")
test.py:4: error: Unsupported operand types for + ("int" and "Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("float" and "_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("float" and "str")
test.py:4: error: Unsupported operand types for + ("float" and "bytes")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]")
test.py:4: error: Unsupported operand types for + ("float" and "Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "str")
test.py:4: error: Unsupported operand types for + ("complex" and "bytes")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]")
test.py:4: error: Unsupported operand types for + ("complex" and "Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("str" and "_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("str" and "bool")
test.py:4: error: Unsupported operand types for + ("str" and "int")
test.py:4: error: Unsupported operand types for + ("str" and "float")
test.py:4: error: Unsupported operand types for + ("str" and "complex")
test.py:4: error: Unsupported operand types for + ("str" and "bytes")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]")
test.py:4: error: Unsupported operand types for + ("str" and "Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[Sequence[Sequence[Sequence[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "_SupportsArray[dtype[Any]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[_SupportsArray[dtype[Any]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[_SupportsArray[dtype[Any]]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[Any]]]]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "bool")
test.py:4: error: Unsupported operand types for + ("bytes" and "int")
test.py:4: error: Unsupported operand types for + ("bytes" and "float")
test.py:4: error: Unsupported operand types for + ("bytes" and "complex")
test.py:4: error: Unsupported operand types for + ("bytes" and "str")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]")
test.py:4: error: Unsupported operand types for + ("bytes" and "Sequence[Sequence[Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]]]")
test.py:4: error: Unsupported left operand type for + ("Sequence[Union[bool, int, float, complex, str, bytes]]")
test.py:4: error: Unsupported operand types for + ("Sequence[Union[bool, int, float, complex, str, bytes]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[Union[bool, int, float, complex, str, bytes]]" and "int")
test.py:4: error: Unsupported operand types for + ("Sequence[Union[bool, int, float, complex, str, bytes]]" and "float")
test.py:4: error: Unsupported operand types for + ("Sequence[Union[bool, int, float, complex, str, bytes]]" and "complex")
test.py:4: error: Unsupported left operand type for + ("Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]" and "bool")
test.py:4: error: Unsupported operand types for + ("Sequence[Sequence[Union[bool, int, float, complex, str, bytes]]]" and "int")
Found 117 errors in 2 files (checked 1 source file)

[aaronspring]

Asking for xarray-contrib/xskillscore#317?

[TomNicholas]

@max-sixty as the self-designated typing expert any ideas?

[max-sixty]

I'd prefer "lauded" than "self-designated" 😄

But unfortunately this looks like strictly a numpy issue, as @raybellwaves pointed out. So I'm not that familiar with it...