Explicit array conversion (e.g., array(), asarray())

Reading through the standard, it appears that we may have missed an important feature: the ability to explicit coerce objects into a desired array type, either from builtin Python types like float/list or other array libraries. In other words, we need something like NumPy’s array() and/or asarray() functions.

[rgommers]

Got a good answer thanks to Pearu: using memoryview(x) in Python will work if and only if an object supports the buffer protocol. So it does not require the Python C API. That makes it less onerous to support, at least in principle (in practice, all libraries will implement it via Python C API calls I’d expect).

[rgommers]

Makes sense. We need only one function I think - asarray and array are almost identical. I’d suggest a mash-up, because neither is ideal:

asarray(obj, dtype=None, copy=False, order='K', ndmin=0)

Some thoughts:

• subok as a keyword doesn’t make too much sense to me, subclasses should be fine if the library allows them.
• order and ndmin make sense for asarray too even though numpy doesn’t have them in asarray.
• what inputs types obj accepts should be very well specified, and stricter than what numpy does. Probably: sequences, generators, and anything with a __dlpack__ method.
• Anything that doesn’t produce a supported dtype should raise an exception.
• No buffer protocol, __array__ or __array_interface__.