[Python-Dev] idea for data-type (data-format) PEP

Greg Ewing greg.ewing at canterbury.ac.nz
Fri Nov 3 00:52:44 CET 2006

Alexander Belopolsky wrote:
> In ctypes arrays of different
> shapes are represented using different types.  As a result, if the object
> exporting its buffer is resized, the datatype object cannot be reused, it
> has to be replaced.

I was thinking about that myself the other day.
I was thinking that both ctypes and NumPy arrays
+ proposed_type_descriptor provide a way of
describing an array of binary data and providing
Python-level access to that data. So a NumPy
array and an instance of a ctypes type that
happens to describe an array are very similar
things. I was wondering whether they could be
unified somehow.

But then I realised that the ctypes array is
a fixed-size array, whereas NumPy's notion of
an array is rather more flexible. So they're not
really the same thing after all.

However, the *elements* of the array are fixed
size in both cases, so the respective descriptions
of the element type could potentially have something
in common.

My current take on the situation is that Travis is
probably right about ctypes types being too
cumbersome for what he has in mind.

The next best thing would be to make them interoperate:
have an easy way of getting a ctypes type corresponding
to a given data layout description and vice versa.


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