> Revising the code example to use an empty array

I think you mean

>>> import array
>>> memoryview(array.array('H', [])).itemsize
2

Your example is an array containing 0, not an empty array - but the conclusion is the same.

> It is technically un-necessary as it can be obtained using PyBuffer_SizeFromFormat

This obviously predicates on `PyBuffer_SizeFromFormat` being implemented, which according to the docs it is not.

> I think that the grammar would allow for an empty record "T{}" that would have itemsize 0 but is of little use inside numpy.

It also allows for records of empty arrays, "T{(0)d:data:}". While these are of little use, they _are_ supported by both ctypes and numpy, so we should support them in the PEP3118 interface used between them.