issues: 1936840711

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1936840711 PR_kwDOAMm_X85cdvXs 8294 Use shape and dtype as typevars in NamedArray 14371165 closed 0     9 2023-10-11T05:08:32Z 2023-12-12T20:41:29Z 2023-10-18T06:22:52Z MEMBER   0 pydata/xarray/pulls/8294

Using a different TypeVar strategy compared to #8281. The idea here is to typevar shape and dtype instead, just like numpy does.

Previously I tried to use the _data array as the TypeVar but that causes all kinds of issues since TypeVar is usually invariant and can't be updated to a new type. Since the dtype changes very frequently when doing array operations it quickly gets difficult to pass along the correct typing.

  • This PR adds a from_array function. The intention is to use that function to create NamedArrays when you are passing around ArrayLikes. The init for NamedArray will now just assume the input data is correct. At runtime at least, mypy will catch any non-supported array types. There's some precedent to this:
  • numpy.array_api.Array forces to use xp.asarray.
  • Cubed assumes the inputs are correct. Has a xp.asarray and a from_array function.
  • The ugly fastpath argument is therefore not needed.
  • Adds a bunch of type hint classes, duckarray[ShapeType, DType] (corresponding to np.ndarray) or DuckArray[ScalarType] (corresponding to np.typing.NDArray) are the recommended ones.
  • It's better to use these kinds of classes over creating is_duck_array functions with typeguards because isinstance also works on the else clause.

  • This PR adds some array_api functions, the idea here is that NamedArray could also be array_api compliant.

  • [x] Tests added

  • [x] Closes #8291

References: https://github.com/tomwhite/cubed/blob/ea885193dd37d27917a24878b51bb086aaef5fb1/cubed/core/ops.py#L34 https://stackoverflow.com/questions/74633074/how-to-type-hint-a-generic-numpy-array https://numpy.org/doc/stable/reference/arrays.scalars.html#scalars https://github.com/numpy/numpy/blob/040ed2dc9847265c581a342301dd87d2b518a3c2/numpy/init.pyi#L1423 https://github.com/numpy/numpy/blob/040ed2dc9847265c581a342301dd87d2b518a3c2/numpy/_typing/_array_like.py#L32 https://stackoverflow.com/questions/69186176/determine-if-subclass-has-a-base-classs-method-implemented-in-python

 
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