On Mon, Jun 4, 2018 at 5:39 AM Matthew Harrigan <harrigan.matt...@gmail.com> wrote:
> Should there be discussion of typing (pep-484) or abstract base classes in > this nep? Are there any requirements on the result returned by > __array_function__? > This is a good question that should be addressed in the NEP. Currently, we impose no limitations on the types returned by __array_function__ (or __array_ufunc__, for that matter). Given the complexity of potential __array_function__ implementations, I think this would be hard/impossible to do in general. I think the best case scenario we could hope for is that type checkers would identify that result of NumPy functions as: - numpy.ndarray if all inputs are numpy.ndarray objects - Any if any non-numpy.ndarray inputs implement the __array_function__ Based on my understanding of proposed rules for typing protocols [1] and overloads [2], I think this could just work, e.g., @overload def func(array: np.ndarray) -> np.ndarray: ... @overload def func(array: ImplementsArrayFunction) -> Any: ... [1] https://www.python.org/dev/peps/pep-0544/ [2] https://github.com/python/typing/issues/253#issuecomment-389262904
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